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  • 1.
    Aili, Daniel
    et al.
    Imperial College London, U.K..
    Mager, M
    Imperial College London, U.K..
    Roche, David
    Imperial College London, U.K..
    Stevens, Molly
    Imperial College London, U.K..
    Hybrid Nanoparticle-Liposome Detection of Phospholipase Activity2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 4, p. 1401-1405Article in journal (Refereed)
    Abstract [en]

    A flexible nanoparticle-based phospholipase (PL) assay is demonstrated in which the enzymatic substrate is decoupled from the nanoparticle surface. Liposomes are loaded with a polypeptide that is designed to heteroassociate with a second polypeptide immobilized on gold nanoparticies. Release of this polypeptide from the liposornes, triggered by PL, induces a folding-dependent nanoparticle bridging aggregation. The colorimetric response from this aggregation enables straightforward and continuous detection of PL in the picomolar range. The speed, specificity, and flexibility of this assay make it appropriate for a range of applications, from point of care diagnostics to high throughput pharmaceutical screening.

  • 2.
    Aili, Daniel
    et al.
    Imperial College London, UK .
    Stevens, Molly M.
    Imperial College London, UK .
    Bioresponsive peptide-inorganic hybrid nanomaterials2010In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 39, no 9, p. 3358-3370Article, review/survey (Refereed)
    Abstract [en]

    Bioanalytical techniques that enable simple, fast and reliable high sensitivity monitoring of biomolecular interactions are of immense importance for diagnostics and drug development. This tutorial review provides an overview of recent progress in the development of peptide-based hybrid nanomaterials that transduce molecular interactions by exploiting the optical and magnetic properties of nanoparticles. Peptides have emerged as an interesting alternative to conventional biomolecular receptors, such as antibodies, and are facilitating the design of responsive hybrid nanomaterials that are both robust and sensitive for biodiagnostic applications.

  • 3.
    Ardic, Madeleine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Gifvars, Anton
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    A study on the effects of the process parameters of polymerised HMDSO using RF-PECVD in corrosion protection applications2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis the effects of the process parameters of pp-HMDSO were studied in the application of corrosion protection of an Al surface. The method for polymerising the HMDSO vapour was RF-PECVD. The following process parameters were studied: RF-power, flow of HMDSO, Oxygen as reactive gas, Ar as inert gas, the effect of applied bias voltage, as well as Ar etch as pre-treatment and subjecting the film to a pure O2 plasma as post-treatment. The results were a prolonging of the total decay time of the Al film when subjected to a 1M NaOH solution. The decay time increased from 5-20s for an unprotected Al film to 140min for the best pp-HMDSO coating. SEM/EDX, XRR, L*a*b* were used when analysing the pp-HMDSO films. The best performing coatings were tested on reflectors and passed the industry standard test of being subjected to a 0.1M NaOH for 5min without visible corrosion or decay.

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  • 4.
    Atakan, Aylin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Erdtman, Edvin
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Mäkie, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts2018In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, p. 55-64Article in journal (Refereed)
    Abstract [en]

    Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.

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  • 5.
    Benselfelt, Tobias
    et al.
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Nordenström, Malin
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Wågberg, Lars
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Explaining the Exceptional Wet Integrity of Transparent Cellulose Nanofibril Films in the Presence of Multivalent Ions: Suitable Substrates for Biointerfaces2019In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 13, no 6, article id 1900333Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) assemble into water‐resilient materials in the presence of multivalent counter‐ions. The essential mechanisms behind these assemblies are ion–ion correlation and specific ion effects. A network model shows that the interfibril attraction indirectly influences the wet modulus by a fourth power relationship to the solidity of the network (Ew ∝ φ4). Ions that induce both ion–ion correlation and specific ion effects significantly reduce the swelling of the films, and due to the nonlinear relationship dramatically increase the wet modulus. Herein, this network model is used to explain the elastoplastic behavior of wet films of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical (TEMPO)‐oxidized, carboxymethylated, and phosphorylated CNFs in the presence of different counter‐ions. The main findings are that the aspect ratio of the CNFs influences the ductility of the assemblies, that the bivalency of phosphorylate ligands probably limits the formation of interfibril complexes with divalent ions, and that a higher charge density increases the friction between fibrils by increasing the short‐range attraction from ion–ion correlation and specific ion effects. These findings can be used to rationally design CNF materials for a variety of applications where wet strength, ductility, and transparency are important, such as biomaterials or substrates for bioelectronics.

  • 6.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Formation mechanisms of covalent nanostructures from density functional theory2016In: Proceedings of International Workshop on On-Surface Synthesis, Cham: Springer, 2016, p. 269-287Conference paper (Refereed)
    Abstract [en]

    In this chapter, it is demonstrated how electronic structure calculations, with focus on density functional theory, can be used to gain insight about on-surface reactions. I first give a brief introduction to how density functional theory can be used to study reactions. The focus is then shifted to two different types of on-surface reactions, highlighting the theoretical work that has been performed to gain detailed atomistic insight into them. First, the state of the art of the theory behind on-surface Ullmann coupling is described. In this reaction, molecular building blocks dehalogenate, which enables them to covalently couple. The most crucial reaction parameters are identified—the diffusion and coupling barriers of surface-supported radicals—and the potential for theory to optimize these is discussed. We then concentrate on the homo-coupling between terminal alkynes, a rudimentarily different process where molecules initially couple before undergoing a dehydrogenation step. The theory of the mechanism behind this coupling strategy is less developed than that of the on-surface Ullmann coupling, where fundamental questions remain to be unraveled. For example, by the subtle change of substrate from Ag to Au, the on-surface alkyne chemistry is completely altered from the homo-coupling to a cyclodehydrogenation reaction for the same molecular building block, of which origin remains unknown. The main objective of the chapter is to give an impression of what kind of information theory can obtain about reaction on surface, as well as to motivate and inspire for future theoretical studies, which will be needed to turn on-surface synthesis into a more predictive discipline.

  • 7.
    Cao, S.
    et al.
    Jiangsu University, Zhenjiang, China.
    Fang, L.
    Jiangsu University, Zhenjiang, China.
    Zhao, Z.
    Jiangsu University, Zhenjiang, China.
    Ge, Yi
    Cranfield University, Bedfordshire, UK.
    Piletsky, Sergey
    Cranfield University, Bedfordshire, UK.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology. University of Cranfield, UK.
    Hierachically Structured Hollow Silica Spheres for High Efficiency Immobilization of Enzymes2013In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Advanced Functional Materials, ISSN 1616-3028, Vol. 23, no 17, p. 2162-2167Article in journal (Refereed)
    Abstract [en]

    In this work, the first example of a hierarchically structured hollow silica system is reported without any chemical modification to the enzyme involved in the process. The leaching of the physically adsorbed enzyme is substantially restrained in comparison to pure hollow silica supports. The hierarchical architecture is composed of the ordered hollow silica spheres with a shell-in-shell structure. This rationally integrated architecture, which serves as the host for glucose oxidase immobilization, displays many significant advantages, including increases in mechanical stability, enzyme loading, and bioactivity, and a decrease in enzyme leaching compared to existing pure hollow silica matrices. This facilitates further multifarious applications for enhanced enzyme immobilization, biosensors, and biocatalysis.

  • 8.
    Chalangar, Ebrahim
    et al.
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering. School of Information Technology, Halmstad University, 301 18, Halmstad, Sweden.
    Nur, Omer
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics.
    Willander, Magnus
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics.
    Gustafsson, Anders
    Solid State Physics and NanoLund, Lund University, Box 118, 221 00, Lund, Sweden.
    Pettersson, Håkan
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering. School of Information Technology, Halmstad University, 301 18, Halmstad, Sweden; Solid State Physics and NanoLund, Lund University, Box 118, 221 00, Lund, Sweden.
    Synthesis of Vertically Aligned ZnO Nanorods Using Sol-gel Seeding and Colloidal Lithography Patterning2021In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 16, no 1, article id 46Article in journal (Refereed)
    Abstract [en]

    Different ZnO nanostructures can be grown using low-cost chemical bath deposition. Although this technique is cost-efficient and flexible, the final structures are usually randomly oriented and hardly controllable in terms of homogeneity and surface density. In this work, we use colloidal lithography to pattern (100) silicon substrates to fully control the nanorods' morphology and density. Moreover, a sol-gel prepared ZnO seed layer was employed to compensate for the lattice mismatch between the silicon substrate and ZnO nanorods. The results show a successful growth of vertically aligned ZnO nanorods with controllable diameter and density in the designated openings in the patterned resist mask deposited on the seed layer. Our method can be used to fabricate optimized devices where vertically ordered ZnO nanorods of high crystalline quality are crucial for the device performance.

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  • 9. Order onlineBuy this publication >>
    Chalangar, Seyed Ebrahim
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering.
    Synthesis and Characterization of ZnO/Graphene Nanostructures for Electronics and Photocatalysis2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Recent rapid development of electronics and electro-optical devices demands affordable and reliable materials with enhanced performance. Forming nanocomposites of already well-known materials is one possible route towards novel functional materials with desirable synergistic enhanced properties. Incompatible chemical properties, mismatched crystal structures and weak bonding interactions between the substances, however, often limit the number of possible nanocomposites. Moreover, using an inexpensive, facile, large-area and flexible fabrication technique is crucial to employ the new composites in industrially viable applications.

    This thesis focuses on the synthesis and characterization of different zinc oxide/graphene (ZnO/GR) nanocomposites, well suited for optoelectronics and photocatalysis applications. Two different approaches of i) substrate-free random synthesis, and ii) template-assisted selective area synthesis were studied in detail. In the first approach, ZnO nanoparticles/rods were grown on GR. The obtained nanocomposites were investigated for better GR dispersity, electrical conductivity and optical properties. Besides, by adding silver iodide to the nanocomposite, an enhanced plasmonic solar-driven photocatalyst was synthesized and analyzed. In the second approach, arrays of single, vertically aligned ZnO nanorods were synthesized using a colloidal lithography-patterned sol-gel ZnO seed layer. Our demonstrated nanofabrication technique with simple, substrate independent, and large wafer-scale area compatibility improved the alignment and surface density of ZnO nanorods over large selective growth areas. Eventually, we found a novel method to further enhance the vertical alignment of the ZnO nanorods by introducing a GR buffer layer between the Si substrate and the ZnO seed layer, together with the mentioned patterning technique.

    The synthesized nanocomposites were analyzed using a large variety of experimental techniques including electron microscopy, photoelectron spectroscopy, x-ray diffraction, photoluminescence and cathodoluminescence spectroscopy for in-depth studies of their morphology, chemical and optical properties. Our findings show that the designed ZnO/GR nanocomposites with vertically aligned ZnO nanorods of high crystalline quality, synthesized with the developed low-cost nanofabrication technique, can lead to novel devices offering higher performance at a significantly lower fabrication cost.

    List of papers
    1. Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
    Open this publication in new window or tab >>Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
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    2018 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 41, article id 415201Article in journal (Refereed) Published
    Abstract [en]

    The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (amp;lt;100 degrees C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphene dispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2018
    Keywords
    graphene; zinc oxide; nanorods; nanocomposites; persistent photoconductivity; printing
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-150196 (URN)10.1088/1361-6528/aad3ec (DOI)000440632800001 ()30015332 (PubMedID)2-s2.0-85051665865 (Scopus ID)
    Note

    Funding Agencies|Knowledge Foundation; Linkoping University; Halmstad University

    Available from: 2018-08-22 Created: 2018-08-22 Last updated: 2024-01-08Bibliographically approved
    2. Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
    Open this publication in new window or tab >>Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
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    2019 (English)In: RSC Advances, E-ISSN 2046-2069, Vol. 9, no 52, p. 30585-30598Article in journal (Refereed) Published
    Abstract [en]

    High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.

    Place, publisher, year, edition, pages
    Royal Meteorological Society, 2019
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-160568 (URN)10.1039/C9RA06273D (DOI)000487989300064 ()
    Note

    Funding agencies: Department of Science and Technology (ITN) at Campus Norrkoping, Linkoping University, Sweden; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation

    Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2024-01-08Bibliographically approved
    3. Synthesis of Vertically Aligned ZnO Nanorods Using Sol-gel Seeding and Colloidal Lithography Patterning
    Open this publication in new window or tab >>Synthesis of Vertically Aligned ZnO Nanorods Using Sol-gel Seeding and Colloidal Lithography Patterning
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    2021 (English)In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 16, no 1, article id 46Article in journal (Refereed) Published
    Abstract [en]

    Different ZnO nanostructures can be grown using low-cost chemical bath deposition. Although this technique is cost-efficient and flexible, the final structures are usually randomly oriented and hardly controllable in terms of homogeneity and surface density. In this work, we use colloidal lithography to pattern (100) silicon substrates to fully control the nanorods' morphology and density. Moreover, a sol-gel prepared ZnO seed layer was employed to compensate for the lattice mismatch between the silicon substrate and ZnO nanorods. The results show a successful growth of vertically aligned ZnO nanorods with controllable diameter and density in the designated openings in the patterned resist mask deposited on the seed layer. Our method can be used to fabricate optimized devices where vertically ordered ZnO nanorods of high crystalline quality are crucial for the device performance.

    Place, publisher, year, edition, pages
    Springer, 2021
    National Category
    Condensed Matter Physics Materials Chemistry Nano Technology
    Identifiers
    urn:nbn:se:liu:diva-174072 (URN)10.1186/s11671-021-03500-7 (DOI)000627791200001 ()33709294 (PubMedID)
    Note

    Funding: Lund University; AForsk Foundation [19-725]; Halmstad University; Linkoping University; Crafoord Foundation

    Available from: 2021-03-12 Created: 2021-03-12 Last updated: 2021-04-12Bibliographically approved
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  • 10. Order onlineBuy this publication >>
    Chen, Yu-Hsiang
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Mechanical and thermal stability of hard nitride coatings2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hard coating’s thermal stability is essential due to the high temperature environment of high-speed cutting applications, while the phase and microstructure evolution induced by exposing the coating to high temperature affects the mechanical properties. In this thesis, the mechanical stability of arc-evaporated, hard, transition metal nitride coatings annealed at high temperature is analyzed and related to the phase and microstructure evolution. In addition to hardness, fracture toughness is evaluated by surface and cross-sectional investigations by scanning/transmission electron microscopy of damage events following mechanical tests.

    The crack resistance of Ti1xAlxN with a range of Al content (x = 0.23-0.82) was studied by contact fatigue tests, where the differences in the microstructure were found to play a major role. Superior mechanical properties were found in Ti0.63Al0.37N; in the as-deposited state as a result of a favorable grain size, and after annealing at 900o C due to the microstructure formed during spinodal decomposition.

    The mechanical and high-temperature properties of hard coatings can be enhanced by alloying or multi-layering. Within this work, quaternary Ti-Al-X-N (X = Cr, Nb and V) alloys were studied and superior toughness was found for TiAl(Nb)N in both the as-deposited and annealed (1100C) states. The hexagonal (h)-AlN formation in cubic (c)-TixAl0.37Cr10.37xN (x = 0.03 and 0.16) was analyzed by in-situ x-ray scattering during annealing. The energy for h-AlN formation was found to be dependent on the microstructure evolution during annealing, which varies with the coating composition.

    High Al content h-ZrAlN/c-TiN and h-ZrAlN/c-ZrN multilayers were investigated through scratch tests followed by focused ion-beam analysis of the crack propagation. A c-Ti(Zr)N phase forms in h-ZrAlN/c-TiN multilayers at high temperatures and that contributes to enhanced hardness and fracture toughness by keeping the semi-coherent sub-interfaces.

    Finally, an in-situ analysis of coatings by x-ray scattering during a turning process was carried out. It demonstrates the possibility of observation of stress evolution and thermal expansion of the coatings or the work piece material during machining. This experiment provides real-time information on the coating behavior during cutting.

    List of papers
    1. Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys
    Open this publication in new window or tab >>Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys
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    2017 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 691, p. 1024-1032Article in journal (Refereed) Published
    Abstract [en]

    The phase evolution of cubic (c), solid solution TixCr-0.37Al1-0.37-x N alloys with x = 0.03 and 0.16, and the kinetics of the hexagonal (h)-AlN formation are studied via in situ wide angle x-ray scattering experiments during high temperature (1000-1150 degrees C) annealing. Spinodal decomposition was observed in Ti0.16Cr0.36Al0.48N while Ti0.03Cr0.38Al0.59N decomposes through nucleation and growth of h-AlN, c-TiN and c-CrAlN. h-AlN is formed from c-CrAlN domains in both cases and the formation rate of h-AlN depends on the stability of the c-CrAlN domains. In Ti0.16Cr0.36Al0.48N, the c-CrAlN domains are stabilized by crystallographic coherency with the surrounding c-TiCrN in a microstructure originating from spinodal decomposition. This results in lower formation rates of h-AlN for this composition. These differences are reflected in higher activation energy for h-AlN formation in Ti0.16Cr0.36Al0.48N compared to Ti0.03Cr0.38Al0.59N. It also points out different stabilities of the intermediate phase c-CrAlN during phase decomposition of TiCrAlN alloys. Additional contributions to the low activation energy for formation of h-AlN in Ti0.03Cr0.38Al0.59N stems from precipitation at grain boundaries. (C) 2016 Elsevier B.V. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2017
    Keywords
    Coating materials; Phase transitions; Kinetics; Synchrotron radiation
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:liu:diva-132647 (URN)10.1016/j.jallcom.2016.08.299 (DOI)000386227900124 ()
    Note

    Funding Agencies|EUs Erasmus-Mundus graduate school in Material Science and Engineering (DocMASE); Swedish Research Council VR [621- 2012-4401]; Rontgen-Angstrom Cluster grant [VR 2011-6505]; Swedish Foundation for Strategic Research, SSF [RMA08-0069]; Swedish government strategic research area grant AFM - SFO MatLiU [2009-00971]; VINNOVA (M - Era.net project) [2013-02355]

    Available from: 2016-11-21 Created: 2016-11-18 Last updated: 2021-12-29
    2. Thermal and mechanical stability of wurtzite-ZrA1N/cubic-TiN and wurtzite-ZrA1N/cubic-ZrN multilayers
    Open this publication in new window or tab >>Thermal and mechanical stability of wurtzite-ZrA1N/cubic-TiN and wurtzite-ZrA1N/cubic-ZrN multilayers
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    2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 324, p. 328-337Article in journal (Refereed) Published
    Abstract [en]

    The phase stability and mechanical properties of wurtzite (w)-Zr(0.25)A1(0.75)N/cubic (c)-TiN and w-Zr(0.25)A1(0.75)N/c-ZrN multilayers grown by arc evaporation are studied. Coherent interfaces with an orientation relation of c-TiN (111)[1-10]IIw-ZrAlN (0001)[11-20] form between ZrA1N and TiN sublayers during growth of the w-ZrAIN/c-TiN multilayer. During annealing at 1100 degrees C a c-Ti(Zr)N phase forms at interfaces between ZrA1N and TiN, which reduces the lattice mismatch so that the coherency and the compressive strain are partially retained, resulting in an increased hardness (32 GPa) after annealing. For the w-ZrAIN/c-ZrN multilayer, there is no coherency between sublayers leading to strain relaxation during annealing causing the hardness to drop. The retained coherency between layers and the compressive strain in the w-ZrAIN/c-TiN multilayer results in superior fracture toughness compared to the w-ZrAIN/c-ZrN multilayer as revealed by cross-sectional investigations of damage events under scratch and indentation tests. (C) 2017 Elsevier B.V. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2017
    Keywords
    Multilayers; ZrAIN coatings; Scratch test; Fracture toughness; Arc evaporation
    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:liu:diva-140035 (URN)10.1016/j.surfcoat.2017.05.055 (DOI)000406988200037 ()
    Note

    Funding Agencies|EUs Erasmus-Mundus Graduate School in Material Science and Engineering (DocMASE); Swedish Research Council VR [621-2012-4401, 2011-6505]; Swedish Government Strategic Research Area Grant AFM - SFO MatLiU [VINNOVA 2009-00971]; Competence center on Functional Nanoscale Materials, FunMat-II [VINNOVA 2016-05156]

    Available from: 2017-08-29 Created: 2017-08-29 Last updated: 2022-12-19
    3. Enhanced thermal stability and fracture toughness of TiAlN coatings by Cr, Nb and V-alloying
    Open this publication in new window or tab >>Enhanced thermal stability and fracture toughness of TiAlN coatings by Cr, Nb and V-alloying
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    2018 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 342, p. 85-93Article in journal (Refereed) Published
    Abstract [en]

    The effect of metal alloying on mechanical properties including hardness and fracture toughness were investigated in three alloys, Ti 0.33Al0.50(Me) 0.17N (Me = Cr, Nb and V), and compared to Ti0.50Al0.50N, in the as-deposited state and after annealing. All studied alloys display similar as-deposited hardness while the hardness evolution during annealing is found to be connected to phase transformations, related to the alloy’s thermal stability. The most pronounced hardening was observed in Ti0.50Al0.50N, while all the coatings with additional metal elements sustain their hardness better and they are harder than Ti0.50Al0.50N after annealing at 1100 °C. Fracture toughness properties were extracted from scratch tests. In all tested conditions, as-deposited and annealed at 900 and 1100 °C, Ti0.33Al0.50Nb0.17N show the least surface and sub-surface damage when scratched despite the differences in decomposition behavior and h-AlN formation. Theoretically estimated ductility of phases existing in the coatings correlates well with their crack resistance. In summary, Ti0.33Al0.50Nb0.17N is the toughest alloy in both as-deposited and post-annealed states.

    Place, publisher, year, edition, pages
    Elsevier, 2018
    Keywords
    Thermal stability, Quaternary transition metal nitrides, Scratch test, Fracture toughness, Arc evaporation
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-147842 (URN)10.1016/j.surfcoat.2018.02.059 (DOI)000440120700010 ()2-s2.0-85042726396 (Scopus ID)
    Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2022-12-19Bibliographically approved
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    Mechanical and thermal stability of hard nitride coatings
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  • 11.
    Chey, Chan Oeurn
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Patra, Hirak K
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Tengdelius, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Golabi, Mohsen
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Parlak, Onur
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Imani, Roghayeh
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Elhag, Sami A. I.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Yandi, Wetra
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Tiwari, Ashutosh
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Impact of nanotoxicology towards technologists to end users2013In: Advanced Materials Letters, ISSN 0976-3961, E-ISSN 0976-397X, Vol. 4, no 8, p. 591-597Article in journal (Refereed)
    Abstract [en]

    The length scale for nanomaterial is small enough to be invisible and presume innocence for the initial avoidance of the toxicity issues. Again it was beyond the understanding of the time frame when nanotechnology just blooms that a length scale itself might be an important toxic parameter apart from its materialistic properties. We present this report to address the fundamental issues and questions related to the nanotoxicity issues from laboratory to the land of applications. We emphasize about the basic nanoscale materials that are regularly being used by the scientific community and the nanotechnology based materials that has already in the market or will come soon.

  • 12.
    de la Rica, Roberto
    et al.
    Imperial College London, UK.
    Aili, Daniel
    Imperial College London, UK and Nanyang Technological University, Singapore.
    Stevens, Molly
    Imperial College London, UK.
    Enzyme-responsive nanoparticles for drug release and diagnostics2012In: Advanced Drug Delivery Reviews, ISSN 0169-409X, E-ISSN 1872-8294, Vol. 64, no 11, p. 967-978Article, review/survey (Refereed)
    Abstract [en]

    Enzymes are key components of the bionanotechnology toolbox that possess exceptional biorecognition capabilities and outstanding catalytic properties. When combined with the unique physical properties of nanomaterials, the resulting enzyme-responsive nanoparticles can be designed to perform functions efficiently and with high specificity for the triggering stimulus. This powerful concept has been successfully applied to the fabrication of drug delivery schemes where the tissue of interest is targeted via release of cargo triggered by the biocatalytic action of an enzyme. Moreover, the chemical transformation of the carrier by the enzyme can also generate therapeutic molecules, therefore paving the way to design multimodal nanomedicines with synergistic effects. Dysregulation of enzymatic activity has been observed in a number of severe pathological conditions, and this observation is useful not only to program drug delivery in vivo but also to fabricate ultrasensitive sensors for diagnosing these diseases. In this review, several enzyme-responsive nanomaterials such as polymer-based nanoparticles, liposomes, gold nanoparticles and quantum dots are introduced, and the modulation of their physicochemical properties by enzymatic activity emphasized. When known, toxicological issues related to the utilization nanomaterials are highlighted. Key examples of enzyme-responsive nanomaterials for drug delivery and diagnostics are presented, classified by the type of effector biomolecule, including hydrolases such as proteases, lipases and glycosidases, and oxidoreductases.

  • 13.
    Domènech-Gil, Guillem
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering. Institute of Nanoscience and Nanotechnology (IN2UB), Department of Electronic and Biomedical Engineering, Universitat de Barcelona (UB), Barcelona, Spain.
    Gràcia, Isabel
    Institut de Microelectrònica de Barcelona (IMB), Centre Nacional de Microelectrònica (CNM), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
    Cané, Carles
    Institut de Microelectrònica de Barcelona (IMB), Centre Nacional de Microelectrònica (CNM), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
    Romano-Rodríguez, Albert
    Institute of Nanoscience and Nanotechnology (IN2UB), Department of Electronic and Biomedical Engineering, Universitat de Barcelona (UB), Barcelona, Spain.
    Nitrogen Dioxide Selective Sensor for Humid Environments Based on Octahedral Indium Oxide2021In: Frontiers in Sensors, E-ISSN 2673-5067, Vol. 2, article id 672516Article in journal (Refereed)
    Abstract [en]

    We report the growth of micrometer-sized In2O3 octahedral structures, which are next aligned in chains using dielectrophoresis on top of microhotplates with prepatterned electrodes and integrated heater to work as chemoresistive gas sensors. The devices are relatively fast (180 s), highly sensitive (response up to ∼256%), and selective toward NO2 in humid environments, showing little response to O2 and ethanol, and being completely insensitive to CO and CH4. The here-presented fabrication method can be easily extended as a cost-effective post-process in CMOS-compatible microhotplate fabrication and, thus, represents a promising candidate for indoor and outdoor air quality monitoring devices.

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  • 14. Order onlineBuy this publication >>
    Dorri, Samira
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnetron Sputter Epitaxy of CrB2/TiB2 Diboride Superlattice Thin Films2024Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Artificial superlattices with their exceptional properties have been popular in a broad range of applications such as electronic, magnetic, optical, and hard coating. Another potential application for single crystal artificial superlattices is highly efficient interference neutron optics, owing to an ultimate interface width of just ±½ atomic layer. Moreover, studies of superlattices have been instrumental in understanding the hardening mechanisms in transition metal nitrides and carbides while such studies on transition metal diborides is lacking, despite extensive studies on monolithic transition metal diboride thin films.

    This work is an initiative to grow CrB2/TiB2 (0001) diboride superlattices epitaxially onto Al2O3 (0001) substrates by direct current magnetron sputter epitaxy implementing two different approaches; compound diboride targets, and co-sputtering of a metal target with a compound target. Effects of substrate temperature, B stoichiometry (B/TM ratio), modulation period Λ = DCrB2 + DTiB2, layer thickness ratio , and relative applied power to magnetrons on the structural and interface quality of superlattices are studied and discussed.

    Using compound targets, superlattices with thickness ratio Γ = 0.3 and modulation periods Λ between 1 and 10 nm, and with Λ = 6 nm and thickness ratios between 0.2 to 0.8 were synthesized at the optimum sputter gas pressure of pAr = 4 mTorr and a substrate temperature of 600 °C. It is found that superlattices with Λ = 6 nm and Γ in the range of 0.2-0.4 exhibit the highest structural quality. However, B segregation in the over-stoichiometric TiBy layers (y > 2), grown from TiB2 compound target, results in narrow epitaxial superlattice columnar growth with structurally distorted B-rich boundaries. By co-sputtering from Ti and TiB2 targets, y could be reduced from 3.3 to 0.9 in TiBy layers through controlling the relative applied target power. Co-sputtered TiBy single layers and superlattices were grown at substrate temperatures between 600 and 900 °C. 300-nm-thick TiB2.3 single layers grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films.A significant enhancement for close-tostoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm was achieved at 750 °C. X-ray diffraction, time of flight elastic recoil detection analysis, scanning transmission electron microscopy, electron energy loss spectroscopy, selected area electron diffraction, and nano-indentation are used for characterization.

    List of papers
    1. Effects of stoichiometry and individual layer thickness ratio on the quality of epitaxial CrBx/TiBy superlattice thin films
    Open this publication in new window or tab >>Effects of stoichiometry and individual layer thickness ratio on the quality of epitaxial CrBx/TiBy superlattice thin films
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    2023 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 228, article id 111842Article in journal (Refereed) Published
    Abstract [en]

    Studies of single crystal artificial superlattices (SLs) of transition-metal (TM) diborides, which is instru- mental to understand hardening mechanisms at nanoscale, is lacking. Here, CrBx/TiBy (0001) diboride SLs [x,y E 1.7-3.3] are grown epitaxially on Al2O3(0001) substrates by direct-current magnetron sputter epitaxy. Growth conditions for obtaining well-defined SLs with good interface quality are found at 4 mTorr Ar pressure and 600 degrees C. 1 -mu m-thick SL films deposited with modulation periods A between 1 and 10 nm, and A=6 nm SLs with TiBy-to-A layer thickness ratios F ranging from 0.2 to 0.8 are studied. SLs with A=6 nm and F in the range of 0.2-0.4, with a near stoichiometric B/TM ratio, exhibit the high- est structural quality. The effects of F and stoichiometries (B/TM ratio) on the distribution of B in the SL structures are discussed. By increasing the relative thickness of TiBy, the crystalline quality of SLs starts to deteriorate due to B segregation in over-stoichiometric TiBy, resulting in narrow epitaxial SL columnar growth with structurally-distorted B-rich boundaries. Moreover, increasing the relative thickness of under-stoichiometric CrBx enhances the SL quality and hinders formation of B-rich boundaries. The SLs are found to exhibit hardness values in the range of 29-34 GPa.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2023
    Keywords
    Diborides; Superlattices; Thin films; Thickness ratio; Modulation period; Stoichiometry
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-194825 (URN)10.1016/j.matdes.2023.111842 (DOI)000998208000001 ()
    Note

    Funding Agencies|Swedish National Graduate School in Neutron Scattering (SwedNess); Swedish Foundation for Strategic Research (SSF) [GSn15 -0008]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials (AFM) at Linkoeping University (Faculty Grant SFO Mat LiU) [2009 00971]; Swedish Research Council VR [2019-00191, 2021-00357]; Knut and Alice Wallenberg Foundation [KAW 2015.0043]

    Available from: 2023-06-14 Created: 2023-06-14 Last updated: 2024-01-12
    2. Enhanced quality of single crystal CrBx/TiBy diboride superlattices by controlling boron stoichiometry during sputter deposition
    Open this publication in new window or tab >>Enhanced quality of single crystal CrBx/TiBy diboride superlattices by controlling boron stoichiometry during sputter deposition
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    2024 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, article id 159606Article in journal (Refereed) Published
    Abstract [en]

    Single-crystal CrB2/TiB2 diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiBy using a single TiB2 target deteriorates the structural quality of CrBx/TiBy (0001) superlattices. We study the influence of co-sputtering of TiB2 + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiBy single layers and CrBx/TiBy (0001) superlattices on Al2O3(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures TS ranging from 600 to 900 °C. By controlling the relative applied powers to the TiB2 and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB2.3 grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm grown at 750 °C showed the highest single crystal quality and best layer definition. TiB2.3 layers display rough top interfaces indicating kinetically limited growth while CrB1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.

    Place, publisher, year, edition, pages
    Elsevier, 2024
    Keywords
    Superlattice, Diboride, Thin film, Co-sputtering, Nanostructure
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-200730 (URN)10.1016/j.apsusc.2024.159606 (DOI)001183388000001 ()
    Note

    Funding: Swedish National Graduate School in Neutron Scattering (SwedNess), Swedish Foundation for Strategic Research (SSF) GSn15 - 0008, Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials (AFM) at Linköping University (Faculty Grant SFO Mat LiU No. 2009 00971), Center in Nanoscience and technology at LiTH CeNano, Hans Werthén Foundation (IVA), Society of Vacuum Coaters Foundation (SVCF), Swedish Research Council (VR) Grant numbers 2019-00191 (for accelerator-based ion-technological center in tandem accelerator laboratory in Uppsala University), VR and SSF for access to ARTEMI, the Swedish National Infrastructure in Advanced Electron Microscopy (2021-00171 and RIF21-0026), Knut and Alice Wallenberg Foundation for the support of the electron microscopy laboratory at Linköping University (KAW 2015.0043), VR 2021-00159 for the Swedish neutron reflectometer SuperADAM at ILL 10.5291/ILL-DATA.CRG-2964, and Plansee GmbH for providing diboride targets.

    Available from: 2024-02-06 Created: 2024-02-06 Last updated: 2024-04-12Bibliographically approved
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  • 15.
    Erdtman, Edvin
    et al.
    Akademin för textil, teknik och ekonomi, Högskolan i Borås, Borås, Sverige.
    Bohlén, Martin
    Akademin för textil, teknik och ekonomi, Högskolan i Borås, Borås, Sverige.
    Ahlström, Peter
    Akademin för textil, teknik och ekonomi, Högskolan i Borås, Borås, Sverige.
    Gkourmpis, Thomas
    Innovation & Technology, Borealis AB, Stenungsund, Sweden.
    Berlin, Mikael
    Tetra Pak Packaging Solutions AB, Ruben Rausings Gata, Lund, Sweden.
    Andersson, Thorbjörn
    Tetra Pak Packaging Solutions AB, Ruben Rausings Gata, Lund, Sweden.
    Bolton, Kim
    Akademin för textil, teknik och ekonomi, Högskolan i Borås, Borås, Sverige.
    A molecular-level computational study of the diffusion and solubility of water and oxygen in carbonaceous polyethylene nanocomposites2016In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 54, no 5, p. 589-602Article in journal (Refereed)
    Abstract [en]

    Monte Carlo and molecular dynamics simulations were performed to investigate the effect on the solubility, diffusion, and permeability of water and oxygen when adding graphene or single-walled carbon nanotubes (SWCNTs) to polyethylene (PE). When compared with pure PE, addition of graphene lowered the solubility of water, whereas at lower temperatures, the oxygen solubility increased because of the oxygen–graphene interaction. Addition of SWCNTs lowered the solubility of both water and oxygen when compared with pure PE. A detailed analysis showed that an ordered structure of PE is induced near the additive surface, which leads to a decrease in the diffusion coefficient of both penetrants in this region. The addition of graphene does not change the permeation coefficient of oxygen (in the direction parallel to the filler) and, in fact, may even increase this coefficient when compared with pure PE. In contrast, the water permeability is decreased when graphene is added to PE. The addition of SWCNTs decreases the permeability of both penetrants. Graphene can consequently be added to selectively increase the solubility and permeation of oxygen over water, at least at lower temperatures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 589–602

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  • 16.
    Eriksson, Peter
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    A new synthesis of nanoparticles designed for Biomedical Imaging. A pilot study.2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a new procedure for synthesizing nanoparticles with fluorescent and MRI contrast enhancement properties. The produced nanoparticles consist of mixtures between two well-known materials; zinc oxide and gadolinium oxide. Zinc oxide is a well-known semiconductor with visible fluorescence and gadolinium oxide is a paramagnetic material exhibiting excellent magnetic properties for enhancing contrast in MRI. 

    The presented synthesis is based on a recently published protocol by Zhang et al [1], for synthesis of pure zinc oxide nanoparticles. The procedure includes a precursor synthesis where respectively metal is dissolved in a solution of water and methacrylic acid. Thereafter the precursors are mixed and dissolved in TEG for a combined nucleation and in-situ polymerization step.

    The work in this thesis is multidisciplinary involving molecular design, chemical synthesis, nanoparticle preparation, purification, characterization and also biological applications. The first rounds of nanoparticles were readily dispersible in water, had adequate fluorescent properties, were in a size range suited for in vivo applications and had better relaxivity properties compared to commonly used contrast agent. These results motivate future work including further optimizations of the protocol. This new nanomaterial has high potential as contrast agent for biomedical imaging.

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    Final Thesis
  • 17. Order onlineBuy this publication >>
    Eskilson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Biophysics and bioengineering. Linköping University, Faculty of Science & Engineering.
    Multifunctional Nanocellulose Composite Materials2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanoparticles (NPs) are particles with more than one dimension between 1 and 100 nm. Because of their small size, they typically display different physical and chemical properties than the corresponding bulk materials. NPs have been used in many different applications, such as in electronics, optics, catalysis, and in biomedicine. Due to their colloidal nature, NPs are often immobilized on a solid substrate, such as glass or polymer-based materials, including biopolymers. Nanocellulose is a biopolymerbased nanomaterial that can be obtained from plants or bacterial biofilms. They can be processed into thin and highly hydrated films with high mechanical strength and can serve as a versatile substrate for NPs. Bacterial cellulose (BC) is also an interesting material for generating wound dressings. The combination of NPs and BC results in soft and flexible nanocomposites (BC-NPs) that can demonstrate novel properties and improve the functionality of wound dressings. 

    BC-NP nanocomposites have previously been obtained by impregnating BC with the reactants needed for synthesis of the NPs and allowing the reaction to proceed in situ, inside and on the surface of the BC. This strategy limits the possibilities to control NP geometry and NP concentration and make synthesis of nanocomposites with more sophisticated compositions very challenging. In addition, the synthesis conditions used can potentially have negative effects on the properties of BC. 

    The work presented in this thesis shows the possibility to produce well-defined, tunable BC-NP nanocomposites using self-assembly under very benign conditions that enable functionalization of BC with a wide range of different types of NPs. In addition to exploring the self-assembly process and the physical properties of these new BC-NP composites, several different applications were investigated. The functionalization of BC with gold nanoparticles (AuNPs) of different sizes and geometries was demonstrated. The resulting materials were used for development of a new sensor transduction technology, exploiting the optical response upon mechanical compression to detect biomolecules. BC-AuNP nanocomposites were also developed for monitoring of protease activity of wound pathogens, for catalysis, and for fabrication of ultra-black materials with unique absorption and scattering profiles of light in the visible and near infrared spectral range. In addition, the self-assembly process could be adopted for generating BC-mesoporous silica nanoparticles (MSNs) nanocomposite wound dressings. The resulting high surface area materials could be used as carriers for pH sensitive dyes. The pH-responsive BC-MSNs demonstrated adequate biocompatibility and allowed for monitoring of wound pH and for assessment of wound status. 

    The strategies for functionalization of BC with inorganic NPs that was developed and explored in this thesis are highly versatile and allow for fabrication of a wide range of multifunctional nanocomposite materials. 

    List of papers
    1. Self-Assembly of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle Composites
    Open this publication in new window or tab >>Self-Assembly of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle Composites
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    2020 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 30, no 40, article id 2004766Article in journal (Refereed) Published
    Abstract [en]

    Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC-NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self-assembly strategy is described for fabrication of complex and well-defined BC-NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self-assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near-field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.

    Place, publisher, year, edition, pages
    WILEY-V C H VERLAG GMBH, 2020
    Keywords
    antimicrobials; bacterial cellulose; gold nanoparticles; nanocomposite; sensors
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-168770 (URN)10.1002/adfm.202004766 (DOI)000557380700001 ()
    Note

    Funding Agencies|Swedish Foundation for Strategic Research (SFF)Swedish Foundation for Strategic Research [FFL15-0026, RMX18-0039]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; VinnovaVinnova [2016-05156]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [KAW 2016.0231]; Swedish Research CouncilSwedish Research Council [2017-05178, 2015-05002]; Spanish Ministerio de Ciencia, Innovacion y Universidades (MICINN) [MAT2016-77391-R]; Severo Ochoa Centres of Excellence programme - Spanish Research Agency (AEI) [SEV-2017-0706]

    Available from: 2020-08-31 Created: 2020-08-31 Last updated: 2023-05-24
    2. Nanocellulose composite wound dressings for real-time pH wound monitoring
    Open this publication in new window or tab >>Nanocellulose composite wound dressings for real-time pH wound monitoring
    Show others...
    2023 (English)In: Materials Today Bio, ISSN 2590-0064, Vol. 19, article id 100574Article in journal (Refereed) Published
    Abstract [en]

    The skin is the largest organ of the human body. Wounds disrupt the functions of the skin and can have catastrophic consequences for an individual resulting in significant morbidity and mortality. Wound infections are common and can substantially delay healing and can result in non-healing wounds and sepsis. Early diagnosis and treatment of infection reduce risk of complications and support wound healing. Methods for monitoring of wound pH can facilitate early detection of infection. Here we show a novel strategy for integrating pH sensing capabilities in state-of-the-art hydrogel-based wound dressings fabricated from bacterial nanocellulose (BC). A high surface area material was developed by self-assembly of mesoporous silica nanoparticles (MSNs) in BC. By encapsulating a pH-responsive dye in the MSNs, wound dressings for continuous pH sensing with spatiotemporal resolution were developed. The pH responsive BC-based nanocomposites demonstrated excellent wound dressing properties, with respect to conformability, mechanical properties, and water vapor transmission rate. In addition to facilitating rapid colorimetric assessment of wound pH, this strategy for generating functional BC-MSN nanocomposites can be further be adapted for encapsulation and release of bioactive compounds for treatment of hard-to-heal wounds, enabling development of novel wound care materials.

    Place, publisher, year, edition, pages
    Elsevier, 2023
    Keywords
    Bacterial nanocellulose, Wound dressing, pH sensor, Infection, Mesoporous silica nanoparticles
    National Category
    Biomaterials Science
    Identifiers
    urn:nbn:se:liu:diva-192408 (URN)10.1016/j.mtbio.2023.100574 (DOI)000944392500001 ()36852226 (PubMedID)
    Note

    Funding agencies: This work was supported by the Swedish Foundation for Strategic Research (SFF) grant no. FFL15-0026 and framework grant RMX18-0039 (HEALiX), the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU no. 2009–00971), the competence center FunMat-II that is financially supported by Vinnova (grant no. 2016-05156), the Knut and Alice Wallenberg Foundation (grant no. KAW 2016.0231), the Swedish Research Council (VR) (grant no. 2021-04427) and Swedish strategic research program Bio4Energy. Illustrations were created with BioRender.com. We thank S2Medical AB, Linköping, Sweden, for providing BC.

    Available from: 2023-03-15 Created: 2023-03-15 Last updated: 2024-05-01Bibliographically approved
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  • 18.
    Fernández del Río, Lia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    A Mueller Matrix Spectroscopic Ellipsometry Study of Scarab Beetles of the Chrysina Genus2012Conference paper (Other academic)
    Abstract [en]

    The attractive shiny metallic colour of jewel scarabs is originating from the structure of the exoskeleton.For some directions and wavelengths of the incident light this structure will also cause the reflectedlight to have a large ellipticity (near-circular polarization). This is due to that the exoskeleton is ahelicoidal structure, formed by layers of chitin molecules. The reflected light is most commonly lefthandedpolarized but right-handed polarization is also observed. In this work six species of Scarabbeetles from the Chrysina genus are investigated. The complete Mueller-matrix is measured with adual rotating compensator ellipsometer (RC2, J.A.Woollam Co., Inc.). The results are presented ascontour plots where we represent different parameters as a function of incidence angle 2[25; 75]and wavelength 2[240; 1000]nm of the incident beam. Parameters of particular interest are the m41element of the Mueller-matrix, which is related to the circular polarization behaviour, the degree ofpolarization, the ellipticity and the absolute value of the azimuth angle. From ocular observationsthrough left- and right-circularly polarizing filters all specimens showed clear polarization effects interms of colour changes. However, the Mueller matrix ellipsometry measurements showed two generaltypes of polarization behaviour depending on the studied species. Chrysina macropus and Chrysinaperuviana had a smaller range of m41 values around zero. Much larger m41 variations were observedfor Chrysina argenteola, Chrysina chrysargyrea and Chrysina resplendens. Chrysina gloriosa hadboth types of polarization behaviour depending on if the measurements where made on the green orgolden parts of this striped beetle. Comparisons among samples of beetles from the same species wereconducted. For instance, different specimens of Chrysina resplendens show rather large differences inthe polarization response whereas specimens of Chrysina chrysargyrea showed very similar polarizationbehaviour. All studied specimens did in some sense reflect both right- and left-handed polarizedlight. In many cases very high ellipticities (near-circular polarization states) were observed. Modelsof structures generating the observed polarization effects as well as biological aspects will also bediscussed.Figure 257: Three pictures of C. chrysargyrea from left to right taken with aleft-circular polarizer, no filters and with a right-circular polarizer in front of thecamera. Two contour plots of m41 for C. chrysargyrea showing a large region withleft-handed near-circular polarization and C. resplendens showing a large regionwith right-handed near-circular polarization.

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  • 19. Order onlineBuy this publication >>
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Micro-photoluminescence and micro-Raman spectroscopy of novel semiconductor nanostructures2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Low-dimensional semiconductor structures, such as one-dimensional nanowires (NWs) and zerodimensional quantum dots (QDs), are materials with novel fundamental physical properties and a great potential for a wide range of nanoscale device applications. Here, especially promising are direct bandgap II-VI and III-V compounds and related alloys with a broad selection of compositions and band structures. For examples, NWs based on dilute nitride alloys, i.e. GaNAs and GaNP, provide both an optical active medium and well-shaped cavity and, therefore, can be used in a variety of advanced optoelectronic devices including intermediate band solar cells and efficient light-emitters. Self-assembled InAs QDs formed in the GaAs matrix are proposed as building blocks for entangled photon sources for quantum cryptography and quantum information processing as well as for spin light emitting devices. ZnO NWs can be utilized in a variety of applications including efficient UV lasers and gas sensors. In order to fully explore advantages of nanostructured materials, their electronic properties and lattice structure need to be comprehensively characterized and fully understood, which is not yet achieved in the case of aforementioned material systems. The research work presented this thesis addresses a selection of open issues via comprehensive optical characterization of individual nanostructures using micro-Raman ( -Raman) and micro-photoluminescence ( -PL) spectroscopies.

    In paper 1 we study polarization properties of individual GaNP and GaP/GaNP core/shell NWs using polarization resolved μ-PL spectroscopy. Near band-edge emission in these structures is found to be strongly polarized (up to 60% at 150K) in the orthogonal direction to the NW axis, in spite of their zinc blende (ZB) structure. This polarization response, which is unusual for ZB NWs, is attributed to the local strain in the vicinity of the N-related centers participating in the radiative recombination and to their preferential alignment along the growth direction, presumably caused by the presence of planar defects. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to control the polarization anisotropy of III-V nanowires, advantageous for their applications as a nanoscale source of polarized light.

    Structural and optical properties of novel coaxial GaAs/Ga(N)As NWs grown on Si substrates, were evaluated in papers 2-4. In paper 2 we show by using -Raman spectroscopy that, though nitrogen incorporation shortens a phonon correlation length, the GaNAs shell with [N]<0.6% has a low degree of alloy disorder and weak residual strain. Additionally, Raman scattering by the GaAs-like and GaNlike phonons is found to be enhanced when the excitation energy approaches the E+ transition energy. This effect was attributed the involvement of intermediate states that were created by N-related clusters in proximity to the E+ subband. Recombination processes in these structures were studied in paper 3 by means of μ-PL, μ-PL excitation (μ-PLE), and time-resolved PL spectroscopies. At low temperatures, the alloy disorder is found to localize photo-excited carriers leading to predominance of localized exciton (LE) transitions in the PL spectra. Some of the local fluctuations in N composition are suggested to create three-dimensional confining potentials equivalent to that for QDs, based on the observation of sharp PL lines within the LE contour. In paper 4 we show that the formation of these QD-like confinement potentials is somewhat facilitated in spatial regions of the NWs with a high density of structural defects, based on correlative spatially-resolved structural and optical studies. It is also concluded the principal axis of these QD-like local potentials is mainly oriented along the growth direction and emit light that is linearly polarized in the direction orthogonal to the NW axis. At room temperature, the PL emission is found to be dominated by recombination of free carriers/excitons and their lifetime is governed by non-radiative recombination via surface states. The surface recombination is found to become less severe upon N incorporation due to N-induced modification of the surface states, possibly due to partial surface nitridation. All these findings suggest that the GaNAs/GaAs hetero-structures with the onedimensional geometry are promising for fabrication of novel optoelectronic devices on foreign substrates (e.g. Si).

    Fine-structure splitting (FSS) of excitons in semiconductor nanostructures has significant implications in photon entanglement, relevant to quantum information technology and spintronics. In paper 5 we study FSS in various laterally-arranged single quantum molecular structures (QMSs), including double QDs (DQDs), quantum rings (QRs), and QD-clusters (QCs), by means of polarization resolved μ-PL spectroscopy. It is found that FSS strongly depends on the geometric arrangements of the QMSs, which can effectively tune the degree of asymmetry in the lateral confinement potential of the excitons and can reduce FSS even in a strained QD system to a limit similar to strain-free QDs.

    Fabrication of nanostructured ZnO-based devices involves, as a compulsory step, deposition of thin metallic layers. In paper 6 we investigate impact of metallization by Ni on structural quality of ZnO NWs by means of Raman spectroscopy. We show that Ni coating of ZnO NWs causes passivation of surface states responsible for the enhanced intensity of the A1(LO) in the bare ZnO NWs. From the resonant Raman studies, strong enhancement of the multiline Raman signal involving A1(LO) in the ZnO/Ni NWs is revealed and is attributed to the combined effects of the Fröhlich interaction and plasmonic coupling. The latter effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for utilizing such structures as efficient nano-sized gas sensors.

    List of papers
    1. Origin of strong photoluminescence polarization in GaNP nanowires
    Open this publication in new window or tab >>Origin of strong photoluminescence polarization in GaNP nanowires
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    2014 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 9, p. 5264-5269Article in journal (Refereed) Published
    Abstract [en]

    The III-V semiconductor nanowires (NWs) have a great potential for applications in a variety of future electronic and photonic devices with enhanced functionality. In this work, we employ polarization resolved micro-photoluminescence (µ-PL) spectroscopy to study polarization properties of light emissions from individual GaNP and GaP/GaNP core/shell nanowires (NWs) with average diameters ranging between 100 and 350 nm. We show that the near-band-edge emission, which originates from the GaNP regions of the NWs, is strongly polarized (up to 60 % at 150 K) in the direction perpendicular to the NW axis. The polarization anisotropy can be retained up to room temperature. This polarization behavior, which is unusual for zinc blende NWs, is attributed to local strain in the vicinity of the N-related centers participating in the radiative recombination and to preferential alignment of their principal axis along the growth direction. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to tailor the polarization anisotropy of III-V nanowires, advantageous for their applications as nanoscale emitters of polarized light.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    Keywords
    Nanowire; photoluminescence; polarization
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-109932 (URN)10.1021/nl502281p (DOI)000341544500053 ()25162940 (PubMedID)
    Available from: 2014-08-28 Created: 2014-08-28 Last updated: 2017-12-05Bibliographically approved
    2. Structural properties of GaNAs nanowires probed by micro-Raman spectroscopy
    Open this publication in new window or tab >>Structural properties of GaNAs nanowires probed by micro-Raman spectroscopy
    2016 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 31, no 2, article id 025002Article in journal (Refereed) Published
    Abstract [en]

    GaNAs-based nanowires (NWs) form a novel material system of potential importance for applications in advanced optoelectronic and photonic devices, thanks to the advantages provided by band-structure engineering, one-dimensional architecture and the possibility to combine them with mainstream silicon technology. In this work we utilize the micro-Raman scattering technique to systematically study the structural properties of such GaAs/GaNAs core/shell NW structures grown by molecular beam epitaxy on a Si substrate. It is shown that the employed one-dimensional architecture allows the fabrication of a GaNAs shell with a low degree of alloy disorder and weak residual strain, at least within the studied range of nitrogen (N) compositions [N] < 0.6%. Raman scattering by the GaAs-like and GaN-like phonons is found to be enhanced when the excitation energy approaches the E + transition energy. Since this effect is found to be more pronounced for the GaN-like phonons, the involved intermediate states are concluded to be localized in proximity to N impurities, i.e. they likely represent N-related cluster states located in proximity to E + .

    Place, publisher, year, edition, pages
    IOP Publishing, 2016
    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-123937 (URN)10.1088/0268-1242/31/2/025002 (DOI)000372412900004 ()
    Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
    3. Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires
    Open this publication in new window or tab >>Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires
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    2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 25, p. 253106-Article in journal (Refereed) Published
    Abstract [en]

    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (mu-PL) and mu-PL excitation (mu-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation. (C) 2014 AIP Publishing LLC.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2014
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-113778 (URN)10.1063/1.4905090 (DOI)000346914000026 ()
    Available from: 2015-02-02 Created: 2015-01-30 Last updated: 2019-06-28
    4. Strongly polarized quantum-dot-like light emitters embedded in GaAs/GaNAs core/shell nanowires
    Open this publication in new window or tab >>Strongly polarized quantum-dot-like light emitters embedded in GaAs/GaNAs core/shell nanowires
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    2016 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, no 35, p. 15939-15947Article in journal (Refereed) Published
    Abstract [en]

    Recent developments in fabrication techniques and extensive investigations of the physical properties of III-V semiconductor nanowires (NWs), such as GaAs NWs, have demonstrated their potential for a multitude of advanced electronic and photonics applications. Alloying of GaAs with nitrogen can further enhance the performance and extend the device functionality via intentional defects and heterostructure engineering in GaNAs and GaAs/GaNAs coaxial NWs. In this work, it is shown that incorporation of nitrogen in GaAs NWs leads to formation of three-dimensional confining potentials caused by short-range fluctuations in the nitrogen composition, which are superimposed on long-range alloy disorder. The resulting localized states exhibit a quantum-dot like electronic structure, forming optically active states in the GaNAs shell. By directly correlating the structural and optical properties of individual NWs, it is also shown that formation of the localized states is efficient in pure zinc-blende wires and is further facilitated by structural polymorphism. The light emission from these localized states is found to be spectrally narrow (similar to 50-130 mu eV) and is highly polarized (up to 100%) with the preferable polarization direction orthogonal to the NW axis, suggesting a preferential orientation of the localization potential. These properties of self-assembled nano-emitters embedded in the GaNAs-based nanowire structures may be attractive for potential optoelectronic applications.

    Place, publisher, year, edition, pages
    Royal Society of Chemistry, 2016
    Keywords
    GaNAs, nanowires, core/shell structures, defects, light emission, polarization
    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-123938 (URN)10.1039/c6nr05168e (DOI)000382839100014 ()
    Note

    Funding agencies: Financial support by the Swedish Energy Agency (grant # P40119-1) and the Swedish Research Council (grants # 2015-05532 and 2008-405) is greatly appreciated. The Knut and Alice Wallenberg Foundation is gratefully acknowledged for support of the Electron Microscopy laboratory in Linkoping.

    Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2020-06-11Bibliographically approved
    5. Exciton Fine-Structure Splitting in Self-Assembled Lateral InAs/GaAs Quantum-Dot Molecular Structures
    Open this publication in new window or tab >>Exciton Fine-Structure Splitting in Self-Assembled Lateral InAs/GaAs Quantum-Dot Molecular Structures
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    2015 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 6, p. 5741-5749Article in journal (Refereed) Published
    Abstract [en]

    Fine-structure splitting (FSS) of excitons in semiconductor nanostructures is a key parameter that has significant implications in photon entanglement and polarization conversion between electron spins and photons, relevant to quantum information technology and spintronics. Here, we investigate exciton FSS in self-organized lateral InAs/GaAs quantum-dot molecular structures (QMSs) including laterally aligned double quantum dots (DQDs), quantum-dot clusters (QCs), and quantum rings (QRs), by employing polarization-resolved microphotoluminescence (μPL) spectroscopy. We find a clear trend in FSS between the studied QMSs depending on their geometric arrangements, from a large FSS in the DQDs to a smaller FSS in the QCs and QRs. This trend is accompanied by a corresponding difference in the optical polarization directions of the excitons between these QMSs, namely, the bright-exciton lines are linearly polarized preferably along or perpendicular to the [11̅0] crystallographic axis in the DQDs that also defines the alignment direction of the two constituting QDs, whereas in the QCs and QRs, the polarization directions are randomly oriented. We attribute the observed trend in the FSS to a significant reduction of the asymmetry in the lateral confinement potential of the excitons in the QRs and QCs as compared with the DQDs, as a result of a compensation between the effects of lateral shape anisotropy and piezoelectric field. Our work demonstrates that FSS strongly depends on the geometric arrangements of the QMSs, which effectively tune the degree of the compensation effects and are capable of reducing FSS even in a strained QD system to a limit similar to strain-free QDs. This approach provides a pathway in obtaining high-symmetry quantum emitters desirable for realizing photon entanglement and spintronic devices based on such nanostructures, utilizing an uninterrupted epitaxial growth procedure without special requirements for lattice-matched materials combinations, specific substrate orientations, and nanolithography.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2015
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-118007 (URN)10.1021/acsnano.5b01387 (DOI)000356988500013 ()25965972 (PubMedID)
    Available from: 2015-05-20 Created: 2015-05-20 Last updated: 2018-09-05
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  • 20.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Optical properties of novel semiconductor nanostructures2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Semiconductor nanostructures, such as one-dimensional nanowires (NWs) and zerodimensional quantum dots (QDs), have recently gained increasing interest due to their unique physical properties that are found attractive for a wide variety of applications ranging from gas sensing and spintronics to optoelectronics and photonics. Here, especially promising are nanostructures based on compound semiconductors, including ZnO, GaNP and GaAs/InAs. For examples, ZnO NWs are used for gas sensing. They also serve as an active material in UV light sources, owing to its wide band gap combined with a large exciton binding energy. GaNP NWs are a novel material system that allows realization of efficient amber lightemitting diodes and novel intermediate-band solar cells with an anticipated high efficiency. InAs QDs formed in the GaAs matrix are efficient emitters of near IR light and can be utilized in future spin-functional devices for applications in spintronics and quantum information processing. The realization of the full potential of semiconductor nanostructures requires detailed knowledge of their electronic and structural properties which is far from being complete at the present stage of research. In this thesis we address some of these important issues using optical characterization techniques, such as micro-Raman and  microphotoluminescence (μ-PL) spectroscopies.

    In paper I we use Raman spectroscopy to investigate effects of metallization by nickel on electronic and structural properties of ZnO/Ni core/shell NWs. We show that coating ZnO NWs with Ni shells causes passivation of surface states whereas subsequent annealing leads to formation of new defects, evident from appearance of the corresponding local vibrational modes. Ni coating is also found to strongly enhance the multiline Raman signal involving A1(LO) phonon scattering, based on the performed resonant Raman studies. This is attributed to an enhanced Fröhlich interaction at the ZnO/Ni heterointerface combined with coupling of the scattered light with local surface plasmons excited in the Ni shell. The latter effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for utilizing such structures as efficient nano-sized gas sensors.

    In paper II we study polarization properties of GaNP nanowires and related axial structures. By employing polarization resolved μ-PL spectroscopy performed on a single NW, we show that alloying with nitrogen allows one to achieve strong orthogonal polarization of light emission even in zinc-blende nanowires of various diameters and that the polarization anisotropy can be retained up to room temperature. This polarization response, which is unusual for zinc blende NWs, is attributed to the local strain in the vicinity of the N-related centers participating in the radiative recombination and to the preferential alignment of their principal axis along the growth direction. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to control the polarization anisotropy of III-V nanowires, advantageous for their applications as nanoscale emitters of polarized light.

    In paper III we investigate exciton fine-structure splitting (FSS) in self-organized InGaAs/GaAs nanostructures including laterally-aligned double quantum dots (DQDs), quantum-dot clusters (QCs) and quantum rings (QRs), by employing polarization resolved μ-PL spectroscopy. We find a clear trend in FSS between the studied nanostructures depending on their geometric arrangements, from a large FSS in the DQDs to a smaller FSS in the QCs and QRs with an overall higher geometric symmetry. This trend is accompanied by a corresponding difference in the polarization directions of the excitonic emissions between these nanostructures, namely, the bright-exciton lines are linearly polarized along or perpendicular to a specific crystallographic axis in the DQDs structure that also defines the alignment of the two QDs, whereas in the QCs and QRs the polarization directions are randomly oriented. We attribute these trends to the interplay between intrinsic effects, such as a statistic shape deviation, atomistic randomness and strain-induced piezoelectricity. Our work demonstrates that FSS can be effectively controlled by geometric engineering of the nanostructures, capable of reducing FSS to the limit similar to strain-free QDs and thus providing a new pathway in fabricating high-symmetry quantum emitters desirable for realizing photon entanglement and spintronic devices based on such nanostructures.

    List of papers
    1. Effects of Ni-coating on ZnO nanowires: A Raman scattering study
    Open this publication in new window or tab >>Effects of Ni-coating on ZnO nanowires: A Raman scattering study
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    2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 21, p. 214302-1-214302-6Article in journal (Refereed) Published
    Abstract [en]

    Structural properties of ZnO/Ni core/shell nanowires (NWs) are studied in detail by means of Raman spectroscopy. It is shown that formation of the Ni shell leads to passivation of surface states responsible for the observed enhanced intensity of the A1(LO) Raman mode of the bare ZnO NWs. It also causes appearance of 490 cm−1 and 710 cm−1 modes that are attributed to local vibrational modes of a defect/impurity (or defects/impurities). This defect is concluded to be preferably formed in annealed ZnO/Ni NWs and is unlikely to contain a Ni atom, as the same Raman modes were also reported for the Ni-free ZnO nanostructures. From our resonant Raman studies, we also show that the ZnO/Ni core/shell NWs exhibit an enhanced Raman signal with a multiline structure involving A1(LO). This observation is attributed to combined effects of an enhanced Fröhlich interaction at the ZnO/Ni heterointerface and coupling of the scattered light with local surface plasmons excited in the Ni shell. The plasmonic effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for applications of such structures as efficient nano-sized gas sensors.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2013
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-93878 (URN)10.1063/1.4807912 (DOI)
    Available from: 2013-06-11 Created: 2013-06-11 Last updated: 2017-12-06Bibliographically approved
    2. Origin of strong photoluminescence polarization in GaNP nanowires
    Open this publication in new window or tab >>Origin of strong photoluminescence polarization in GaNP nanowires
    Show others...
    2014 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 9, p. 5264-5269Article in journal (Refereed) Published
    Abstract [en]

    The III-V semiconductor nanowires (NWs) have a great potential for applications in a variety of future electronic and photonic devices with enhanced functionality. In this work, we employ polarization resolved micro-photoluminescence (µ-PL) spectroscopy to study polarization properties of light emissions from individual GaNP and GaP/GaNP core/shell nanowires (NWs) with average diameters ranging between 100 and 350 nm. We show that the near-band-edge emission, which originates from the GaNP regions of the NWs, is strongly polarized (up to 60 % at 150 K) in the direction perpendicular to the NW axis. The polarization anisotropy can be retained up to room temperature. This polarization behavior, which is unusual for zinc blende NWs, is attributed to local strain in the vicinity of the N-related centers participating in the radiative recombination and to preferential alignment of their principal axis along the growth direction. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to tailor the polarization anisotropy of III-V nanowires, advantageous for their applications as nanoscale emitters of polarized light.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    Keywords
    Nanowire; photoluminescence; polarization
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-109932 (URN)10.1021/nl502281p (DOI)000341544500053 ()25162940 (PubMedID)
    Available from: 2014-08-28 Created: 2014-08-28 Last updated: 2017-12-05Bibliographically approved
    3. Control of exciton fine-structure splitting in geometrically engineered self-assembled InAs/GaAs quantum molecular structures
    Open this publication in new window or tab >>Control of exciton fine-structure splitting in geometrically engineered self-assembled InAs/GaAs quantum molecular structures
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    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Fine-structure splitting (FSS) of excitons in semiconductor nanostructures is a key parameter that has significant implications in photon entanglement and polarization conversion between electron spins and photons, relevant to quantum information technology and spintronics. Here, we investigate exciton FSS in self-organized InAs/GaAs quantum molecular structures (QMSs) including laterally-aligned double quantum dots (DQDs), quantum-dot clusters (QCs) and quantum rings (QRs), by employing polarization-resolved micro-photoluminescence spectroscopy. We find a clear trend in FSS between the studied QMSs depending on their geometric arrangements, from a large FSS in the DQDs to a smaller FSS in the QCs and QRs with an overall higher geometric symmetry. This trend is accompanied by a corresponding difference in the optical polarization directions of the excitons between these QMSs, namely, the bright-exciton lines are linearly polarized preferably along or perpendicular to the [11̅0] crystallographic axis in the DQDs that also defines the alignment of the two constituting QDs, whereas in the QCs and QRs the polarization directions are randomly oriented. We attribute the observed trends in the FSS to a significant reduction of the anisotropic strain field in the high symmetry QCRs and QCs as compared with the low-symmetry  DQDs. Our work demonstrates that FSS can be effectively controlled by geometric engineering of the QMSs, capable of reducing FSS even in a strained QD system to a limit similar to strain-free QDs. This approach provides a new pathway in obtaining high-symmetry quantum emitters desirable for realizing photon entanglement and spintronic devices based on such nanostructures, without special requirements for lattice-matched materials combinations, specific substrate orientations and nanolithography.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-112353 (URN)
    Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-03-27Bibliographically approved
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  • 21.
    Flint, Jennifer
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Höst, Gunnar
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Schönborn, Konrad
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Virtual nanoworlds for learning2020In: 21st Century Nanoscience – A Handbook: Public Policy, Education, and Global Trends (Volume Ten) / [ed] Klaus D. Sattler, Boca Raton: CRC Press, 2020, p. 7-1-7-14Chapter in book (Other academic)
    Download full text (pdf)
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  • 22.
    Flint, Jennifer
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Höst, Gunnar
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Schönborn, Konrad
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Virtual Nanoworlds for Learning2020Data set
    Download full text (zip)
    NanoSim software
  • 23.
    Flint, Jennifer
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Höst, Gunnar
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Schönborn, Konrad
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Virtual nanoworlds for learning2020In: 21st Century Nanoscience – A Handbook: Public Policy, Education, and Global Trends (Volume Ten) / [ed] Klaus D. Sattler, Boca Raton: CRC Press, 2020, p. 7-1-7-14Chapter in book (Other academic)
    Download full text (pdf)
    fulltext
  • 24. Order onlineBuy this publication >>
    Forsén, Rikard
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Multicomponent Alloying for Improved Hard Coatings2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Coatings are vital to protect and to increase the productivity of cutting tools in high speed and dry cutting applications. During the cutting operation the temperature may exceed 1000 ºC it is therefore necessary that the coatings withstand high temperatures. A lot of development and research has been carried out during the last 30 years on finding new coating material systems providing enhanced properties such as adhesion, hardness and oxidation resistance at elevated temperatures. This thesis is based on multicomponent alloying of quaternary transition metal nitride hard coatings with a main focus on Ti-Cr-Al-N coatings. Many different coatings and compositions have been deposited using an industrial scale cathodic arc evaporation deposition system. All deposited coatings contain Al as this element is known to increase the hardness and the oxidation resistance of nitride coatings. The deterioration of the hardness in Al-containing nitride coatings is generally attributed to the transformation of cubic Al-N into hexagonal Al-N and the consequent domain coherency relaxation. This thesis investigates these phenomena on an atomic level providing a deeper understanding of and a way to engineer improved hard nitride coatings. The essence of this thesis is that by adding a third metal to a ternary nitride material system, for example one of the most frequently used Ti-Al-N, it is possible to tune and engineer the thermal stability of the cubic structure and the coherency strain which in turn affects the hardness and the oxidation resistance. The key point is that new intermediate phases in the decomposition process are generated so that the eventual detrimental phases are suppressed and delayed. More specifically, when Cr is added to the Ti-Al-N material system the coatings exhibit an age hardening process up to 1000 ºC caused by spinodal decomposition into coherent TiCr- and AlCr-rich cubic Ti-Cr-Al-N domains. This means that the unstable cubic Ti-Cr-Al-N phase decomposes via yet another unstable cubic Cr-Al-N phase before the detrimental hexagonal transformation of AlN takes place. The hardness is therefore retained up to a higher temperature compared to Ti-Al-N coatings.

    By utilizing multicomponent alloying through addition of Ti to Cr-Al-N coatings the hardness is retained after annealing up to 1100 ºC. This is a dramatic improvement compared to Cr-Al-N coatings. Here the Ti addition promotes the competitive spinodal decomposition into TiCr- and Al-enriched domains suppressing the detrimental hexagonal AlN formation.

    To investigate the effect of multicomponent alloying for other material systems with different mixing free energies and atomic sizes, Zr-containing, Zr-Cr-Al-N and Zr-Ti-Al-N, quaternary nitride coatings have also been deposited. For high Al- and high Zr-containing coatings the cubic solid solution structure is disrupted into a mix of nano-crystalline hexagonal and cubic phases with significantly lower hardness. The results show that the structure and hardness of these coatings are sensitive to the composition and in order to optimize the hardness and thermal stability the composition has to be fine-tuned. Altogether it is shown that through multicomponent alloying and through the control of the coherency strain it is possible to enhance the hardness and the oxidation resistance compared to the ternary system which may lead to new improved functional hard coatings.

    List of papers
    1. Improving thermal stability of hard coating films via a concept of multicomponent alloying
    Open this publication in new window or tab >>Improving thermal stability of hard coating films via a concept of multicomponent alloying
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    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 9, p. 091903-Article in journal (Refereed) Published
    Abstract [en]

    We propose a design route for the next generation of nitride alloys via a concept of multicomponent alloying based on self-organization on the nanoscale via a formation of metastable intermediate products during the spinodal decomposition. We predict theoretically and demonstrate experimentally that quasi-ternary (TiCrAl)N alloys decompose spinodally into (TiCr)N and (CrAl)N-rich nanometer sized regions. The spinodal decomposition results in age hardening, while the presence of Cr within the AlN phase delays the formation of a detrimental wurtzite phase leading to a substantial improvement of thermal stability compared to the quasi-binary (TiAl)N or (CrAl)N alloys.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2011
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-70747 (URN)10.1063/1.3631672 (DOI)000294489300018 ()
    Note

    Funding Agencies|SSF||Swedish Research Council||Gran Gustafsson Foundation for Research in Natural Sciences and Medicine||

    Available from: 2011-09-16 Created: 2011-09-16 Last updated: 2024-01-08
    2. Decomposition and phase transformation in TiCrAlN thin coatings
    Open this publication in new window or tab >>Decomposition and phase transformation in TiCrAlN thin coatings
    2012 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 30, no 6Article in journal (Refereed) Published
    Abstract [en]

    Phase transformations and mechanisms that yield enhanced high temperature mechanical properties of metastable solid solutions of cubic (c)-(TixCryAlz)N coatings are discussed in this paper. Coatings grown by reactive arc evaporation technique with metal composition range y<17 at. % and 45<z<62 at. % are studied and compared with the parent TiAlN material system. The coatings exhibit age hardening up to 1000 ºC which is higher compared to what is observed for TiAlN. In addition, the coatings show a less pronounced hardness decrease when hexagonal (h)-AlN is formed compared to TiAlN. The improved thermal stability is discussed in terms of a lowered coherency stress and a lowered enthalpy of mixing due to the addition of Cr, which results in improved functionality in the working temperature range of 850-1000 ºC of for example cutting tools. Upon annealing up to 1400 ºC the coatings decompose into c-TiN, bcc-Cr and h-AlN. The decomposition takes place via several intermediate phases, c-CrAlN, c-TiCrN and hexagonal (β)-Cr2N. The microstructure  evolution investigated at different stages of spinodal decomposition and phase transformation is correlated to the thermal response and mechanical hardness of the coatings.

    Place, publisher, year, edition, pages
    American Vacuum Society, 2012
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-80179 (URN)10.1116/1.4757953 (DOI)
    Note

    On the day of the defence day the status of this article was: Manuscript

    Available from: 2012-08-22 Created: 2012-08-22 Last updated: 2020-03-19Bibliographically approved
    3. Nanostructuring and coherency strain in multicomponent hard coatings
    Open this publication in new window or tab >>Nanostructuring and coherency strain in multicomponent hard coatings
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    2014 (English)In: APL Materials, E-ISSN 2166-532X, Vol. 2, no 11, p. 116104-Article in journal (Refereed) Published
    Abstract [en]

    Lattice resolved and quantitative compositional characterizations of the microstructure in TiCrAlN wear resistant coatings emerging at elevated temperatures are performed to address the spinodal decomposition into nanometer-sized coherent cubic TiCr- and Al-rich domains. The domains coarsen during annealing and at 1100 ºC, the Al-rich domains include a metastable cubic Al(Cr)N phase containing 9 at.% Cr and a stable hexagonal AlN phase containing less than 1 at.% Cr. The cubic and the hexagonal phases form strained semi-coherent interfaces with each other.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2014
    Keywords
    Age hardening; Spinodal decomposition; Cathodic arc evaporation; Aberration corrected TEM
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-110678 (URN)10.1063/1.4901125 (DOI)000345638800023 ()
    Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2022-10-12Bibliographically approved
    4. Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability
    Open this publication in new window or tab >>Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability
    2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 24, p. 244303-Article in journal (Refereed) Published
    Abstract [en]

    A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti 1−x Cr x N multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti- and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti 1−x Cr x N layers. For x = 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > =0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2013
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-103072 (URN)10.1063/1.4851836 (DOI)000329173200056 ()
    Funder
    Swedish Foundation for Strategic Research
    Available from: 2014-01-13 Created: 2014-01-13 Last updated: 2020-03-19Bibliographically approved
    5. Effects of Ti alloying of AlCrN coatings on thermal stability and oxidation resistance
    Open this publication in new window or tab >>Effects of Ti alloying of AlCrN coatings on thermal stability and oxidation resistance
    2013 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 534, p. 394-402Article in journal (Refereed) Published
    Abstract [en]

    Quaternary cubic (TixCr1 − xAl~ 0.60)1 N1 coatings with 0 < x < 0.33 have been grown using reactive cathodic arc evaporation. When adding Ti the hardness was retained after annealing up to 1100 °C which is a dramatic improvement compared to CrAlN coatings. The coatings showed an age hardening process caused by spinodal decomposition into coherent TiCr- and Al-rich cubic TiCrAlN domains and the formation of hexagonal AlN precipitates and cubic TiCrN domains in the vicinity of the grain boundaries. The improved hardness was attributed to the stabilization of the cubic structure suppressing the formation and growth of hexagonal AlN. Furthermore, the presence of Ti atoms generated incoherent nanometer-sized crystallites within the hexagonal AlN precipitates disrupting the hexagonal lattice during the coarsening process.

    The addition of Ti promoted the formation of a TiO2 layer over Al2O3 resulting in a lower oxidation resistance. However, by tuning the composition it is possible to design coatings to have both good oxidation resistance and good high temperature mechanical stability.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    Keywords
    Age hardening, Spinodal decomposition, Hard coatings, TiAlN, TiCrAlN, Catodic arc evaporation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-93255 (URN)10.1016/j.tsf.2013.03.003 (DOI)000317736700066 ()
    Note

    Funding Agencies|SSF project Designed multicomponent coatings, MultiFilms||

    Available from: 2013-05-28 Created: 2013-05-28 Last updated: 2020-03-19Bibliographically approved
    6. High temperature phase decomposition in TixZryAlzN
    Open this publication in new window or tab >>High temperature phase decomposition in TixZryAlzN
    Show others...
    2014 (English)In: AIP Advances, E-ISSN 2158-3226, Vol. 4, no 12, p. 127147-1-127147-9Article in journal (Refereed) Published
    Abstract [en]

    Through a combination of theoretical and experimental observations we study the high temperature decomposition behavior of c-(TixZryAlzN) alloys. We show that for most concentrations the high formation energy of (ZrAl)N causes a strong tendency for spinodal decomposition between ZrN and AlN while other decompositions tendencies are suppressed. In addition we observe that entropic  effects due to configurational disorder favor a formation of a stable Zr-rich (TiZr)N phase with increasing temperature. Our calculations also predict that at high temperatures a Zr rich (TiZrAl)N disordered phase should become more resistant against the spinodal decomposition despite its high and positive formation energy due to the specific topology of the free energy surface at the relevant concentrations. Our experimental observations confirm this prediction by showing strong tendency towards decomposition in a Zr-poor sample while a Zr-rich alloy shows a greatly reduced decomposition rate, which is mostly attributable to binodal decomposition processes. This result highlights the importance of considering the second derivative of the free energy, in addition to its absolute value in predicting decomposition trends of thermodynamically unstable alloys.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2014
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-110682 (URN)10.1063/1.4905138 (DOI)000347170100078 ()
    Note

    On the day of the defence date the status of this article was Manuscript.

    Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2024-01-08Bibliographically approved
    7. Alloying as a tool for structure and thermal stability engineering of hard coatings
    Open this publication in new window or tab >>Alloying as a tool for structure and thermal stability engineering of hard coatings
    2014 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    A large range of (ZrxAly Cr(100-x-y))1N1 coatings have been deposited using cathodic arc evaporation and annealed at temperatures up to 1100 ºC. The coatings can be divided into three different characteristic categories based on their structure, thermal stability and hardness.

    The first category of coatings, (Al < ~30 % and ~40 % < Zr), are stable cubic solid solutions up to 1100 ºC. The hardness decreases upon annealing because of defect annihilation.

    In the second category, (40 % < Al < 60 % and Zr < 15 %), the coatings decompose into ZrCr- and Al-rich nanometer-sized domains when annealed, which results in a hardness increase.

    In the third category (~67 % < Al), the microstructure contain a mixture of 1-2 nanometer-sized nano-crystalline hexagonal (AlN) and cubic (ZrCrN) phases. These coatings have a significantly lower hardness in the as deposited state but upon annealing the hardness increases significantly.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-110683 (URN)
    Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2020-03-19Bibliographically approved
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    Multicomponent Alloying for Improved Hard Coatings
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  • 25.
    Gervilla Palomar, Víctor
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Metal film growth on weakly-interacting substrates: Stochastic simulations and analytical modelling2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thin films are nanoscale layers of material, with exotic properties useful in diverse areas, ranging from biomedicine to nanoelectronics and surface protection. Film properties are not only determined by their chemical composition, but also by their microstructure and roughness, features that depend crucially on the growth process due to the inherent out-of equilibrium nature of the film deposition techniques. This fact suggest that it is possible to control film growth, and in turn film properties, in a knowledge-based manner by tuning the deposition conditions. This requires a good understanding of the elementary film-forming processes, and the way by which they are affected by atomic-scale kinetics. The kinetic Monte Carlo (kMC) method is a simulation tool that can model film evolution over extended time scales, of the order of microseconds, and beyond, and thus constitutes a powerful complement to experimental research aiming to obtain an universal understanding of thin film formation and morphological evolution.

    In this work, kMC simulations, coupled with analytical modelling, are used to investigate the early stages of formation of metal films and nanostructures supported on weakly-interacting substrates. This starts with the formation and growth of faceted 3D islands, that relies first on facile adatom ascent at single-layer island steps and subsequently on facile adatom upward diffusion from the base to the top of the island across its facets. Interlayer mass transport is limited by the rate at which adatoms cross from the sidewall facets to the island top, a process that determines the final height of the islands and leads non-trivial growth dynamics, as increasing temperatures favour 3D growth as a result of the upward transport. These findings explain the high roughness observed experimentally in metallic films grown on weakly-interacting substrates at high temperatures.

    The second part of the study focus on the next logical step of film formation, when 3D islands come into contact and fuse into a single one, or coalesce. The research reveals that the faceted island structure governs the macroscopic process of coalescence as well as its dynamics, and that morphological changes depend on 2D nucleation on the II facets. In addition, deposition during coalescence is found to accelerate the process and modify its dynamics, by contributing to the nucleation of new facets.

    This study provides useful knowledge concerning metal growth on weakly-interacting substrates, and, in particular, identifies the key atomistic processes controlling the early stages of formation of thin films, which can be used to tailor deposition conditions in order to achieve films with unique properties and applications.

    List of papers
    1. Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates
    Open this publication in new window or tab >>Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates
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    2018 (English)In: Physical Review Materials, E-ISSN 2475-9953, Vol. 2, no 6, article id 063401Article in journal (Refereed) Published
    Abstract [en]

    Vapor condensation on weakly interacting substrates leads to the formation of three-dimensional (3D) nanoscale islands (i.e., nanostructures). While it is widely accepted that this process is driven by minimization of the total film/substrate surface and interface energy, current film-growth theory cannot fully explain the atomic-scale mechanisms and pathways by which 3D island formation and morphological evolution occurs. Here, we use kinetic Monte Carlo simulations to describe the dynamic evolution of single-island shapes during deposition of Ag on weakly interacting substrates. The results show that 3D island shapes evolve in a self-similar manner, exhibiting a constant height-to-radius aspect ratio, which is a function of the growth temperature. Furthermore, our results reveal the following chain of atomic-scale events that lead to compact 3D island shapes: 3D nuclei are first formed due to facile adatom ascent at single-layer island steps, followed by the development of sidewall facets bounding the islands, which in turn facilitates upward diffusion from the base to the top of the islands. The limiting atomic process which determines the island height, for a given number of deposited atoms, is the temperature-dependent rate at which adatoms cross from sidewall facets to the island top. The overall findings of this study provide insights into the directed growth of metal nanostructures with controlled shapes on weakly interacting substrates, including two-dimensional crystals, for use in catalytic and nanoelectronic applications.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2018
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-149345 (URN)10.1103/PhysRevMaterials.2.063401 (DOI)000435337300001 ()
    Note

    Funding Agencies|Linkoping University [Dnr-LiU-2015-01510]; Swedish Research Council [VR-2011-5312, VR-2015-04630, VR2014-5790]; Knut and AliceWallenberg Foundation [KAW2011-0094]

    Available from: 2018-07-02 Created: 2018-07-02 Last updated: 2020-12-15
    2. Dynamics of 3D-island growth on weakly-interacting substrates
    Open this publication in new window or tab >>Dynamics of 3D-island growth on weakly-interacting substrates
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    2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, p. 383-390Article in journal (Refereed) Published
    Abstract [en]

    The growth dynamics of faceted three-dimensional (3D) Ag islands on weakly-interacting substrates are investigated-using kinetic Monte Carlo (kMC) simulations and analytical modelling-with the objective of determining the critical top-layer radius R-c required to nucleate a new island layer as a function of temperature T, at a constant deposition rate. kMC shows that R-c decreases from 17.3 to 6.0 angstrom as T is increased at 25 K intervals, from 300 to 500 K. That is, a higher T promotes top-layer nucleation resulting in an increase in island height-to-radius aspect ratios. This explains experimental observations for film growth on weakly-interacting substrates, which are not consistent with classical homoepitaxial growth theory. In the latter case, higher temperatures yield lower top-layer nucleation rates and lead to a decrease in island aspect ratios. The kMC simulation results are corroborated by an analytical mean field model, in which R-c is estimated by calculating the steady-state adatom density on the island side facets and top layer as a function of T. The overall findings of this study constitute a first step toward developing rigorous theoretical models, which can be used to guide synthesis of metal nanostructures, and layers with controlled shape and morphology, on technologically important substrates, including two-dimensional crystals, for nanoelectronic and catalytic applications.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2019
    Keywords
    Growth; Kinetic Monte Carlo; Nanostructure; Diffusion; Nucleation
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-158910 (URN)10.1016/j.apsusc.2019.05.208 (DOI)000472476200042 ()
    Note

    Funding Agencies|Linkoping University ("LiU Career Contract") [Dnr-LiU-2015-01510]; Swedish Research Council [VR-2015-04630, VR2014-5790]; Knut and Alice Wallenberg Foundation [KAW 2011-0094]

    Available from: 2019-07-20 Created: 2019-07-20 Last updated: 2021-05-22
    3. Coalescence dynamics of 3D islands on weakly-interacting substrates
    Open this publication in new window or tab >>Coalescence dynamics of 3D islands on weakly-interacting substrates
    2020 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1, article id 2031Article in journal (Refereed) Published
    Abstract [en]

    We use kinetic Monte Carlo simulations and analytical modelling to study coalescence of three-dimensional (3D) nanoscale faceted silver island pairs on weakly-interacting fcc(111) substrates, with and without concurrent supply of mobile adatoms from the vapor phase. Our simulations show that for vapor flux arrival rates F < 1 monolayer/second (ML/s) coalescence manifests itself by one of the islands absorbing the other via sidewall facet migration. This process is mediated by nucleation and growth of two-dimensional (2D) layers on the island facets, while the supply of mobile atoms increases the nucleation probability and shortens the time required for coalescence completion. When F is increased above 1 ML/s, coalescence is predominantly governed by deposition from the vapor phase and the island pair reaches a compact shape via agglomeration. The crucial role of facets for the coalescence dynamics is further supported by a mean-field thermodynamic description of the nucleation energetics and kinetics. Our findings explain experimental results which show that two-dimensional film growth morphology on weakly-interacting substrates is promoted when the rate of island coalescence is suppressed. The present study also highlights that deviations of experimentally reported film morphological evolutions in weakly-interacting film/substrate systems from predictions based on the sintering and particle growth theories may be understood in light of the effect of deposition flux atoms on the energetics and kinetics of facet-layer nucleation during coalescence.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2020
    National Category
    Nano Technology
    Identifiers
    urn:nbn:se:liu:diva-163690 (URN)10.1038/s41598-020-58712-1 (DOI)000540299500001 ()32029784 (PubMedID)2-s2.0-85079033789 (Scopus ID)
    Note

    Funding agencies: Linkoping University ("LiU Career Contract") [Dnr-LiU-2015-01510]; Swedish research councilSwedish Research Council [VR-2015-04630]; Olle Engkvist foundation [SOEB 190-312]; Aforsk foundation [AF 19-137]; Linkoping University

    Available from: 2020-02-18 Created: 2020-02-18 Last updated: 2022-09-15Bibliographically approved
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    Metal film growth on weakly-interacting substrates: Stochastic simulations and analytical modelling
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  • 26.
    Gervilla, Víctor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Almyras, Georgios
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Lü, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Coalescence dynamics of 3D islands on weakly-interacting substrates2020In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1, article id 2031Article in journal (Refereed)
    Abstract [en]

    We use kinetic Monte Carlo simulations and analytical modelling to study coalescence of three-dimensional (3D) nanoscale faceted silver island pairs on weakly-interacting fcc(111) substrates, with and without concurrent supply of mobile adatoms from the vapor phase. Our simulations show that for vapor flux arrival rates F < 1 monolayer/second (ML/s) coalescence manifests itself by one of the islands absorbing the other via sidewall facet migration. This process is mediated by nucleation and growth of two-dimensional (2D) layers on the island facets, while the supply of mobile atoms increases the nucleation probability and shortens the time required for coalescence completion. When F is increased above 1 ML/s, coalescence is predominantly governed by deposition from the vapor phase and the island pair reaches a compact shape via agglomeration. The crucial role of facets for the coalescence dynamics is further supported by a mean-field thermodynamic description of the nucleation energetics and kinetics. Our findings explain experimental results which show that two-dimensional film growth morphology on weakly-interacting substrates is promoted when the rate of island coalescence is suppressed. The present study also highlights that deviations of experimentally reported film morphological evolutions in weakly-interacting film/substrate systems from predictions based on the sintering and particle growth theories may be understood in light of the effect of deposition flux atoms on the energetics and kinetics of facet-layer nucleation during coalescence.

    Download full text (pdf)
    fulltext
  • 27.
    Ghani, Mozhdeh
    et al.
    Nanotechnology Institute, Amirkabir University of Technology, Tehran, Iran.
    Mak, Wing Cheung
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Cheung, Kwan Yee
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Montazer, M.
    Nanotechnology Institute, Amirkabir University of Technology, Tehran, Iran.
    Rezaei, B.
    Nanotechnology Institute, Amirkabir University of Technology, Tehran, Iran.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Cross-linked superfine electrospun tragacanth-based biomaterial as scaffolds for tissue engineering2016In: European Cells and Materials, ISSN 1473-2262, E-ISSN 1473-2262, Vol. 31, no Suppl. 1, p. 204-204Article in journal (Refereed)
    Abstract [en]

    Natural polymer-based nanofibrous structures promote cell adhesion and proliferation due to their high surface area/volume ratio, high porosity, and similarity to native extracellular matrix in terms of both chemical composition and physical structure. Gum tragacanth (Tg) is a natural polysaccharides obtained from plants. It is a biocompatible, biodegradable and anionic polysaccharides that has been used extensively as an emulsifier in food and pharmaceutical industries. Despite, its good rheological properties and compatibility, the potential biomedical applications of Tg have not been fully investigated. The objective of the present study was to explore the feasibility of combining Tg with gelatin to fabricate a scaffold that serves as a simple collagen-glycosaminoglycans analog for tissue engineering applications, e.g. as a scaffold for human skin epithelial cells.

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    Cross-linked superfine electrospun tragacanth-based biomaterial as scaffolds for tissue engineering
  • 28. Order onlineBuy this publication >>
    Goyenola, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nanostructured carbon-based thin films: prediction and design2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbon-based thin films are a vast group of materials of great technological importance. Thanks to the different bonding options for carbon, a large variety of structures (from amorphous to nanostructured) can be achieved in the process of film synthesis. The structural diversity increases even more if carbon is combined with relatively small quantities of atoms of other elements. This results in a set of materials with many different interesting properties for a wide range of technological applications.

    This doctoral thesis is about nanostructured carbon-based thin films. In particular, the focus is set on theoretical modeling, prediction of structural features and design of sulfo carbide (CSx) and carbon fluoride (CFx) thin films.

    The theoretical approach follows the synthetic growth concept (SGC) which is based on the density functional theory. The SGC departure point is the fact that the nanostructured films of interest can be modeled as assemblies of low dimensional units (e.g., finite graphene-like model systems), similarly to modeling graphite as stacks of graphene sheets. Moreover, the SGC includes a description of the groups of atoms that act as building blocks (i.e., precursors) during film deposition, as well as their interaction with the growing film.

    This thesis consists of two main parts:

    Prediction: In this work, I show that nanostructured CSx thin films can be expected for sulfur contents up to 20 atomic % with structural characteristics that go from graphite-like to fullerene-like (FL). In the case of CFx thin films, a diversity of structures are predicted depending on the fluorine concentration. Short range ordered structures, such as FL structure, can be expected for low concentrations (up to 5 atomic %). For increasing fluorine concentration, diamond-like and polymeric structures should predominate. As a special case, I also studied the ternary system CSxFy. The calculations show that CSxFy thin films with nanostructured features should be possible to synthesize at low sulfur and fluorine concentrations and the structural characteristics can be described and explained in terms of the binaries CSx and CFx.

    Design: The carbon-based thin films predicted in this thesis were synthesized by magnetron sputtering. The results from my calculations regarding structure and composition, and analysis of precursors (availability and role during deposition process) were successfully combined with the experimental techniques in the quest of obtaining films with desired structural features and understanding their properties.

    List of papers
    1. Fullerene-like CSx: A first-principles study of synthetic growth
    Open this publication in new window or tab >>Fullerene-like CSx: A first-principles study of synthetic growth
    2011 (English)In: CHEMICAL PHYSICS LETTERS, ISSN 0009-2614, Vol. 506, no 1-3, p. 86-91Article in journal (Refereed) Published
    Abstract [en]

    Fullerene-Like (FL) Sulpho-Carbide (CSx) compounds have been addressed by first principles calculations. Geometry optimization and cohesive energy results are presented for the relative stability of precursor species such as C2S, CS2, and C2S2 in isolated form. The energy cost for structural defects, arising from the substitution of C by S is also reported. Similar to previously synthesized FL-CNx and FL-CPx compounds, the pentagon, the double pentagon defects as well as the Stone-Wales defects are confirmed as energetically feasible in CSx compounds.

    Place, publisher, year, edition, pages
    Elsevier Science B.V., Amsterdam., 2011
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-67563 (URN)10.1016/j.cplett.2011.02.059 (DOI)000288987600016 ()
    Note
    Original Publication: Cecilia Goyenola, Gueorgui Kostov Gueorguiev, Sven Stafström and Lars Hultman, Fullerene-like CSx: A first-principles study of synthetic growth, 2011, CHEMICAL PHYSICS LETTERS, (506), 1-3, 86-91. http://dx.doi.org/10.1016/j.cplett.2011.02.059 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2011-04-18 Created: 2011-04-18 Last updated: 2017-05-05
    2. Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide
    Open this publication in new window or tab >>Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide
    2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 39, p. 21124-21131Article in journal (Refereed) Published
    Abstract [en]

    Carbon-based fullerene-like (FL) solid compounds are a new class of materials with extraordinary mechanical properties, which can be tuned by the dopant choice and its concentration. In this work, FL sulfocarbide (CSx) was studied by DFT simulations during synthetic growth with CmSn (m, n andlt;= 2). The energetic and structural effects of S atoms at C sites in a graphene-like network were addressed by geometry optimizations and cohesive energy calculations. Results showed that for S concentrations lower than 10 at. %, smoothly bent pure hexagonal networks predominate. For higher S concentrations, the higher defect concentration leads to stronger deformation of the graphene-like sheets. It was determined that FL-CSx is well-structured (not amorphous) for S contents between 10 and 20 at. %. In contrast to other FL materials, bond rotation mechanisms are not expected to play any significant role during FL-CSx formation, and cross-linking sites are less frequent and may be assimilated in the planar structure during growth. Both quasi-planar networks and cage-like conformations were found to form during the synthetic growth of CSx. The detailed analysis of how CSx structural patterns form during its synthetic growth provides a realistic picture for the deposition of this novel compound by magnetron sputtering.

    Place, publisher, year, edition, pages
    American Chemical Society, 2012
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-84738 (URN)10.1021/jp307347t (DOI)000309375700061 ()
    Note

    Funding Agencies|Swedish Research Council (VR)||VR||

    Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2017-12-07
    3. CF(x): A first-principles study of structural patterns arising during synthetic growth
    Open this publication in new window or tab >>CF(x): A first-principles study of structural patterns arising during synthetic growth
    2011 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 516, no 1-3, p. 62-67Article in journal (Refereed) Published
    Abstract [en]

    Structural and bonding patterns arising from the incorporation of fluorine atoms in a graphene-like network relevant to the deposition of carbon fluoride (CF(x)) films were addressed by first-principles calculations. We find that large N-member (N = 8-12) rings, defects by sheet branching, and defects associated with bond rotation pertain to CF(x). The cohesive energy gains associated with these patterns are similar to 0.2-0.4 eV/at., which is similar to those for a wide range of defects in other C-based nanostructured solids. Fullerene-like CF(x) is predicted for F concentrations below similar to 10 at.%, while CF(x) compounds with higher F content are predominantly amorphous or polymeric.

    Place, publisher, year, edition, pages
    Elsevier, 2011
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-72251 (URN)10.1016/j.cplett.2011.09.045 (DOI)000296582400011 ()
    Note

    Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA)||European Research Council (ERC)||

    Available from: 2011-11-24 Created: 2011-11-24 Last updated: 2017-12-08
    4. CF(x) thin solid films deposited by high power impulse magnetron sputtering: Synthesis and characterization
    Open this publication in new window or tab >>CF(x) thin solid films deposited by high power impulse magnetron sputtering: Synthesis and characterization
    Show others...
    2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 4, p. 646-653Article in journal (Refereed) Published
    Abstract [en]

    Fluorine containing amorphous carbon films (CF(x), 0.16 andlt;= x andlt;= 0.35) have been synthesized by reactive high power impulse magnetron sputtering (HiPIMS) in an Ar/CF(4) atmosphere. The fluorine content of the films was controlled by varying the CF(4) partial pressure from 0 mPa to 110 mPa at a constant deposition pressure of 400 mPa and a substrate temperature of 110 degrees C. The films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by applying elastic recoil detection analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and nanoindentation. First-principles calculations were carried out to predict and explain F-containing carbon thin film synthesis and properties. By geometry optimizations and cohesive energy calculations the relative stability of precursor species including C(2), F(2) and radicals, resulting from dissociation of CF4, were established. Furthermore, structural defects, arising from the incorporation of F atoms in a graphene-like network, were evaluated. All as-deposited CF(x) films are amorphous. Results from X-ray photoelectron spectroscopy and Raman spectroscopy indicate a graphitic nature of CF(x) films with x andlt;= 0.23 and a polymeric structure for films with x andgt;= 0.26. Nanoindentation reveals hardnesses between similar to 1 GPa and similar to 16 GPa and an elastic recovery of up to 98%.

    Place, publisher, year, edition, pages
    Elsevier, 2011
    Keywords
    Fluorine containing carbon thin films, HiPIMS, CF(x), First principle calculations, XPS, TEM
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-72809 (URN)10.1016/j.surfcoat.2011.06.055 (DOI)000297086700011 ()
    Note

    Funding Agencies|Hungarian Academy of Sciences||

    Available from: 2011-12-09 Created: 2011-12-08 Last updated: 2017-12-08
    5. Reactive High Power Impulse Magnetron Sputtering of CFx Thin Films in Mixed Ar/CF4 and Ar/C4F8 Discharges
    Open this publication in new window or tab >>Reactive High Power Impulse Magnetron Sputtering of CFx Thin Films in Mixed Ar/CF4 and Ar/C4F8 Discharges
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The reactive high power impulse magnetron sputtering (HiPIMS) processes of C in Ar/tetrafluoromethane CF4 and Ar/octafluorocyclobutane (c-C4F8) have been characterized. Amorphous carbon fluoride (CFx) films were synthesized at deposition pressure and substrate temperature of 400 mPa and 110 oC, respectively. The CFx film composition was controlled in the range of 0.15 < x < 0.35 by varying the partial pressure of the F-containing gases from 0 mPa to 110 mPa. The reactive plasma was studied employing time averaged positive ion mass spectrometry and the resulting thin films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by elastic recoil detection analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, and water droplet contact angle measurements, respectively. The experimental results were compared to results obtained by first-principles calculations based on density functional theory.

    The modeling of the most abundant precursor fragment from the dissociation of CF4 and C4F8 provided their relative stability, abundance, and reactivity, thus permitting to evaluate the role of each precursor during film growth. Positive ion mass spectrometry of both F plasmas show an abundance of CF+, C+, CF⁺₂, and CF⁺₃ (in this order) as corroborated by first-principles calculations. Only CF⁺₃ exceeded the Ar+ signal in a CF4 plasma. Two deposition regimes are found depending on the partial pressure of the F-containing reactive gas, where films with fluorine contents below 24 at% exhibit a graphitic nature, whereas a polymeric structure applies to films with fluorine contents exceeding 27 at%. Moreover, abundant precursors in the plasma are correlated to the mechanical response of the different CFx thin films. The decreasing hardness with increasing F content can be attributed to the abundance of CF⁺₃ precursor species, weakening the C matrix.

    Keywords
    c-C4F8, CF4, fluorine containing carbon thin films, HiPIMS, CFx, first principle calculations, XPS, TEM, positive ion mass spectrometry
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-90908 (URN)
    Available from: 2013-04-08 Created: 2013-04-08 Last updated: 2017-05-05Bibliographically approved
    6. Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles
    Open this publication in new window or tab >>Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles
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    2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 12, p. 6514-6521Article in journal (Refereed) Published
    Abstract [en]

    Fluorinated carbon-based thin films offer a wide range of properties for many technological applications that depend on the microstructure of the films. To gain a better understanding of the role of fluorine in the structural formation of these films, CFx systems based on graphene-like fragments were studied by first-principles calculations. Generally, the F concentration determines the type of film that can be obtained. For low F concentrations (up to similar to 5 at. %), films with fullerene-like as well as graphite-like features are expected. Larger F concentrations (greater than= 10 at. %) give rise to increasingly amorphous carbon films. Further increasing the F concentration in the films leads to formation of a polymer-like microstructure. To aid the characterization of CFx systems generated by computational methods, a statistical approach is developed.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-106285 (URN)10.1021/jp500653c (DOI)000333578300060 ()
    Available from: 2014-05-06 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
    7. Theoretical prediction and synthesis of CSxFy thin films
    Open this publication in new window or tab >>Theoretical prediction and synthesis of CSxFy thin films
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    2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 17, p. 9527-9534Article in journal (Refereed) Published
    Abstract [en]

    A new carbon-based compound: CSxFy was addressed by density functional theory calculations and synthesized by reactive magnetron sputtering. Geometry optimizations and energy calculations were performed on graphene-like model systems containing sulfur and fluorine atoms. It is shown that [S+F] concentrations in the range of 0−10 at.%, structural ordered characteristics similar to graphene pieces containing ring defects are energetically feasible. The modeling predicts that CSxFy thin films with graphite and fullerene-like characteristics may be obtained for the mentioned concentration range. Accordingly, thin films were synthesized from a graphite solid target and sulfur hexafluoride as reactive gas. In agreement with the theoretical prediction, transmission electron microscopy characterization and selected area electron diffraction confirmed the presence of small ordered clusters with graphitic features in a sample containing 0.4 at.% of S and 3.4 at.% of F.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2016
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-121470 (URN)10.1021/acs.jpcc.6b02718 (DOI)000375631100060 ()
    Note

    funding agencies: Swedish Foundation for Strategic Research (SSF) [RMA11-0029]; Carl Trygger Foundation for Scientific Research; Swedish Research Council [642-2013-8020]; ERC [258509]; Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials at Linkoping University 

    Vid tiden för disputation förelåg publikationen som manuskript

    Available from: 2015-09-21 Created: 2015-09-21 Last updated: 2017-12-04Bibliographically approved
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  • 29.
    He, Ximin
    et al.
    University of Cambridge, England; University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tu, Guoli
    University of Cambridge, England.
    Hasko, David G.
    University of Cambridge, England.
    Huettner, Sven
    University of Cambridge, England.
    Greenham, Neil C.
    University of Cambridge, England.
    Steiner, Ullrich
    University of Cambridge, England.
    Friend, Richard H.
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    University of Cambridge, England; University of Cambridge, England; Radboud University of Nijmegen, Netherlands.
    Formation of Well-Ordered Heterojunctions in Polymer: PCBM Photovoltaic Devices2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 1, p. 139-146Article in journal (Refereed)
    Abstract [en]

    The nanoscale morphology in polymer:PCBM based photovoltaic devices is a major contributor to overall device performance. The disordered nature of the phase-separated structure, in combination with the small length scales involved and the inherent difficulty of reproducing the exact morphologies when spin-coating and annealing thin blend films, have greatly hampered the development of a detailed understanding of how morphology impacts photo voltaic device functioning. In this paper we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer: PCBM heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14) mm(-2)) of interpenetrating nanoscale columnar features (as small as 25 nm; at or below the exciton diffusion length) in the active layer. By comparing device results of different feature sizes and two different polymer: PCBM combinations, we demonstrate how double imprinting can be a powerful tool to systematically study different parameters in polymer photovoltaic devices.

  • 30.
    He, Ximin
    et al.
    University of Cambridge, England; University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tu, Guoli
    University of Cambridge, England.
    Hasko, David
    University of Cambridge, England.
    Huettner, Sven
    University of Cambridge, England.
    Steiner, Ullrich
    University of Cambridge, England; University of Freiburg, Germany.
    Greenham, Neil C.
    University of Cambridge, England.
    Friend, Richard H.
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    University of Cambridge, England; University of Cambridge, England; Radboud University of Nijmegen, Netherlands.
    Formation of Nanopatterned Polymer Blends in Photovoltaic Devices2010In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 10, no 4, p. 1302-1307Article in journal (Refereed)
    Abstract [en]

    In this paper, we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14)/mm(2)) of interpenetrating nanoscale columnar features in the active polymer blend layer. The smallest feature sizes are as small as 25 nm on a 50 nm pitch, which results in a spacing of hererojunctions at or below the exciton diffusion length. Photovoltaic devices based on double-imprinted poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 diyl) (F8TBT)/poly(3-hexylthiophene) (P3HT) films are among the best polymer polymer blend devices reported to date with a power conversion efficiency (PCE, eta(e)) of 1.9%.

  • 31. Order onlineBuy this publication >>
    Hsu, Tun-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Effect of metal ion irradiation on hard coating synthesis by physical vapor deposition2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to understand and control how the ions in the plasma influence the film growth during thin film deposition processes. Two physical vapor deposition (PVD) techniques are investigated, namely magnetron sputtering and cathodic arc evaporation. For magnetron sputtering, the unconventional hybrid high-power impulse and direct current magnetron cosputtering (HiPIMS/DCMS) configuration is used in this work. By synchronizing the substrate bias pulses with the HiPIMS pulses by a time offset and duration, the metal ions from the target material can be selected to impinge the growing film, whereas the contribution of the working gas ions can be effectively reduced. Two aspects are explored, low-mass ion subplantation and heavy-mass ion irradiation.

    The thesis begins with establishing the correlation between N2 pressure and plasma properties of the cathodic arc evaporation process using Ti0.5Al0.5 target. The results show Ti ions are the dominant species, followed by Al+. On the other hand, due to the shorter mean free path of the species with increasing N2 pressure, the ion energies and the effective electron temperature decrease while electron density increases. Consequently, comparing the TiAlN coatings grown at lower and higher N2 pressures, the crystallographic textures changes from cubic 220 to 111 along the growth direction, and the residual stress reduces from compressive (-3.4 GPa) to almost stress-free (0.6 GPa).

    The rest of the thesis addresses the influence of ionized species on microstructures, with a focus on tuning film properties by ions in the plasma. Ti1-x(AlySi1-y)xN coatings (0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00) were deposited with an AlSi-HiPIMS/Ti-DCMS with synchronized substrate bias setup. The results show that the coatings deposited by this method have higher Al and Si solubilities in NaCl-structured TiN than other PVD techniques due to low mass ion subplantations. Additionally, a range of films with different compositions display a combination of high hardness (~ 30 GPa) and low residual stress (s < 0.5 GPa), which highlights the benefits of minimizing the Ar+ incorporation by synchronizing substrate bias to the Al+/Si+-rich portion of the HiPIMS pulses. The selected TiAlSiN coatings were then studied for the crater wear resistance of high-speed cutting performance on ball bearing steel (100Cr6). The effects of phase contents and microstructures on cutting performance are evaluated.

    This is further extended by a study of the influence of neutral and ion fluxes overlap and the subplantation range of low-mass ions. This is accomplished by introducing the 1-fold substrate table rotation, different target-to-substrate distances, and substrate bias voltage in a AlSi-HiPIMS/Ti-DCMS hybrid deposition process. The microstructure and phase analysis show the necessity of overlap between HiPIMS and DCMS fluxes to deposit TiAlSiN solid solutions. The compositional variation of the multilayers can be controlled by the applied substrate bias and table rotational speed. Rotation during deposition may yield coatings comparable in hardness to the ones without rotation at the expense of higher compressive stress.

    The effectiveness of controlling heavy ion irradiation is investigated by replacing external heating with high-mass W+ irradiation to grow dense and hard titanium tungsten carbide (TiWC) coatings by WC-HiPIMS/TiC-DCMS with synchronized bias technique. The ionization degree of W+ are controlled by the peak current density (0.27 ≤ JT ≤ 1.36 A/cm2). The results show that W+ irradiation effectively densified TiWC coatings without external heating. The total energy consumption per hour is reduced by 77% using the HiPIMS/DCMS setup without external heating, yet this TiWC coating is 10 GPa harder than similar coating grown by self-bias DCMS with heating.

    List of papers
    1. Effect of varying N(2)pressure on DC arc plasma properties and microstructure of TiAlN coatings
    Open this publication in new window or tab >>Effect of varying N(2)pressure on DC arc plasma properties and microstructure of TiAlN coatings
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    2020 (English)In: Plasma sources science & technology, ISSN 0963-0252, E-ISSN 1361-6595, Vol. 29, no 9, article id 095015Article in journal (Refereed) Published
    Abstract [en]

    Detailed knowledge of correlations between direct current (DC) cathodic arc deposition process parameters, plasma properties, and the microstructure of deposited coatings are essential for a comprehensive understanding of the DC cathodic arc deposition process. In this study we have probed the plasma, generated by DC arc on a Ti-50 at.% Al cathode in a N(2)ambience, at the growth front of the TiAlN coating. Several consequences of an increasing N(2)pressure are observed, including a decreased electron temperature, an increased electron density, and a loss of energetic ions. As a result, the preferred growth texture switches from 220 to 111. It is also observed that neutrals in the plasma can significantly contribute to the growth of TiAlN coatings.

    Place, publisher, year, edition, pages
    IOP PUBLISHING LTD, 2020
    Keywords
    arc plasma; TiAlN; microstructure
    National Category
    Fusion, Plasma and Space Physics
    Identifiers
    urn:nbn:se:liu:diva-170670 (URN)10.1088/1361-6595/abaeb4 (DOI)000570602600001 ()
    Note

    Funding Agencies|VINN Excellence Center in Research and Innovation on Functional Nanoscale Materials (FunMat-II) [2016-05156]; Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

    Available from: 2020-10-19 Created: 2020-10-19 Last updated: 2023-02-14
    2. Influence of Si content on phase stability and mechanical properties of TiAlSiN films grown by AlSi-HiPIMS/Ti-DCMS co-sputtering
    Open this publication in new window or tab >>Influence of Si content on phase stability and mechanical properties of TiAlSiN films grown by AlSi-HiPIMS/Ti-DCMS co-sputtering
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    2021 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 427, article id 127661Article in journal (Refereed) Published
    Abstract [en]

    Ti1-x(AlySi1-y)xN coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al+/Si+ ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al+/Si+-rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al1.0Si0.0, Al0.9Si0.1, Al0.8Si0.2, and Al0.6Si0.4. X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiNz rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~ 30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than -3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~ 30 GPa) and low residual stress (σ < 0.5 GPa). Such an unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al+/Si+ supplantation effect and minimizes the Ar+ incorporation.

    Place, publisher, year, edition, pages
    Elsevier, 2021
    Keywords
    Thin films, TiAlSiN, Magnetron sputtering, HiPIMS, Al and Si irradiation, Low stress
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-180133 (URN)10.1016/j.surfcoat.2021.127661 (DOI)000718020900001 ()
    Note

    Funding agencies: VINNOVA (FunMat-II project grant no. 2016-05156), the Swedish Research Council (grants no 2017-03813 and 2017-06701), the Swedish government strategic research area grant AFM – SFO MatLiU (2009-00971), the Swedish Research Council VR-RFI (#2017-00646_9) and the Swedish Foundation for Strategic Research (contract RIF14-0053)

    Available from: 2021-10-07 Created: 2021-10-07 Last updated: 2023-02-14
    3. Effects of substrate rotation during AlSi-HiPIMS/Ti-DCMS co-sputtering growth of TiAlSiN coatings on phase content, microstructure, and mechanical properties
    Open this publication in new window or tab >>Effects of substrate rotation during AlSi-HiPIMS/Ti-DCMS co-sputtering growth of TiAlSiN coatings on phase content, microstructure, and mechanical properties
    Show others...
    2023 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 453, article id 128986Article in journal (Refereed) Published
    Abstract [en]

    A combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique is used to deposit Ti0.6Al0.32Si0.08N films with 1-fold substrate table rotation. Layers are grown at two different substrate-target separations, two different rotational speeds, and with different values of substrate bias. The aim is to study the role of (1) overlap between ion and neutral fluxes generated from HiPIMS and DCMS sources, respectively, and (2) the subplantation range of low-mass ions. Results from X-ray diffractometry highlight the necessity of flux intermixing in the formation of the metastable B1-structured TiAlSiN solid solutions. All films grown at short target-to-substrate distance contain the hexagonal AlN phase, as there is essentially no overlap between HiPIMS and DCMS fluxes, thus the Al+ and Si+ subplantation is very limited. Under conditions of high flux intermixing corresponding to larger target-to-substrate distance, no w-AlN forms irrespective of rotational speed (1 or 3 rpm) and bias amplitude (120 or 480 V), indicating that the role of Al+/Si+ and Ti flux overlap is crucial for the phase formation during film growth by HiPIMS/DCMS with substrate rotation. This conclusion is further supported by the fact that the reduction of the bilayer thickness with increasing the target-to-substrate distance (hence increasing flux overlap) is larger for films grown with higher amplitude of the substrate bias, indicative of more efficient Al+/Si+ subplantation into the c-TiN phase. Single-phase films with the hardness close to that of layers grown with stationary substrate table can be achieved, however, at the expense of higher compressive stress.

    Place, publisher, year, edition, pages
    Elsevier, 2023
    Keywords
    Thin films, TiAlSiN, Magnetron sputtering, HiPIMS, Al+ and Si+ irradiation, Substrate rotation
    National Category
    Nano Technology Materials Engineering Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-191778 (URN)10.1016/j.surfcoat.2022.128986 (DOI)000923286500001 ()
    Funder
    Vinnova, 2016-05156Swedish Research Council, 2017-03813Swedish Research Council, 2017-06701
    Note

    Funding: VINNOVA (FunMat-II project) [2016-05156]; Swedish Research Council [2017-03813, 2017-06701]; Swedish government strategic research area grant AFM - SFO MatLiU [2009-00971]

    Available from: 2023-02-14 Created: 2023-02-14 Last updated: 2023-03-16
    4. Dense and hard TiWC protective coatings grown with tungsten ion irradiation using WC-HiPIMS/TiC-DCMS co-sputtering technique without external heating
    Open this publication in new window or tab >>Dense and hard TiWC protective coatings grown with tungsten ion irradiation using WC-HiPIMS/TiC-DCMS co-sputtering technique without external heating
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    2023 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 618, article id 156639Article in journal (Refereed) Published
    Abstract [en]

    Titanium tungsten carbide (TiWC) coatings are deposited by a combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique. No external heating is applied during deposition phase, instead, the thermally driven adatom mobility is substituted by heavy ion irradiation. DCMS sources equipped with titanium carbide targets provide constant neutral fluxes to establish the predominant coating structures, whereas tungsten carbide target in HiPIMS mode serves as the source of heavy metal-ions. Substrate bias of −60 V is synchronized to W+ ion-rich time domains of HiPIMS pulses to minimize the contribution from working gas ions. The influence of W+ ion flux intensity, controlled by varying peak target current density (JT), on film properties is investigated. X-ray photoelectron spectroscopy reveals the presence of over stoichiometric carbon forming an amorphous phase, the amount of which can be fine-tuned by varying JT. Changes in film composition as a function of JT are explained based on the in-situ ion mass spectroscopy analyses. Dense TiWC coatings by hybrid process exhibit hardness higher than 30 GPa, which are comparable to TiWC films deposited by DCMS with dc substrate bias and external heating. The relative energy consumption in the hybrid process is reduced by 77 % as compared to high-temperature DCMS processing.

    Place, publisher, year, edition, pages
    Elsevier, 2023
    National Category
    Condensed Matter Physics Nano Technology
    Identifiers
    urn:nbn:se:liu:diva-191779 (URN)10.1016/j.apsusc.2023.156639 (DOI)000935360500001 ()
    Funder
    Vinnova, 2016-05156Swedish Research Council, 2017-03813Swedish Research Council, 2017-06701
    Note

    Funding: VINNOVA (FunMat-II project ) [2016-05156]; Swedish Research Council [2017-03813, 2017-06701]; Swedish government strategic research area grant AFM - SFO MatLiU [2009- 00971]

    Available from: 2023-02-14 Created: 2023-02-14 Last updated: 2023-03-13Bibliographically approved
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  • 32.
    Hsu, Tun-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Kolozsvári, Szilárd
    Plansee Composite Materials GmbH, Lechbruck am See, DE-86983, Germany.
    Polcik, Peter
    Plansee Composite Materials GmbH, Lechbruck am See, DE-86983, Germany.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Dense and hard TiWC protective coatings grown with tungsten ion irradiation using WC-HiPIMS/TiC-DCMS co-sputtering technique without external heating2023In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 618, article id 156639Article in journal (Refereed)
    Abstract [en]

    Titanium tungsten carbide (TiWC) coatings are deposited by a combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique. No external heating is applied during deposition phase, instead, the thermally driven adatom mobility is substituted by heavy ion irradiation. DCMS sources equipped with titanium carbide targets provide constant neutral fluxes to establish the predominant coating structures, whereas tungsten carbide target in HiPIMS mode serves as the source of heavy metal-ions. Substrate bias of −60 V is synchronized to W+ ion-rich time domains of HiPIMS pulses to minimize the contribution from working gas ions. The influence of W+ ion flux intensity, controlled by varying peak target current density (JT), on film properties is investigated. X-ray photoelectron spectroscopy reveals the presence of over stoichiometric carbon forming an amorphous phase, the amount of which can be fine-tuned by varying JT. Changes in film composition as a function of JT are explained based on the in-situ ion mass spectroscopy analyses. Dense TiWC coatings by hybrid process exhibit hardness higher than 30 GPa, which are comparable to TiWC films deposited by DCMS with dc substrate bias and external heating. The relative energy consumption in the hybrid process is reduced by 77 % as compared to high-temperature DCMS processing.

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  • 33.
    Hsu, Tun-Wei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Christensen, Bjarke Holl
    Danish Technological Institute, Kongsvang Allé 29, DK-8000 Aarhus C, Denmark.
    Almtoft, Klaus Pagh
    Danish Technological Institute, Kongsvang Allé 29, DK-8000 Aarhus C, Denmark.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Kolozsvári, Szilárd
    Plansee Composite Materials GmbH, Lechbruck am See DE-86983, Germany.
    Polcik, Peter
    Plansee Composite Materials GmbH, Lechbruck am See DE-86983, Germany.
    Bolz, Stephan
    CemeCon AG, Adenauerstr. 20 A4, D-52146 Wűrselen, Germany.
    Kölker, Werner
    CemeCon AG, Adenauerstr. 20 A4, D-52146 Wűrselen, Germany.
    Schiffers, Christoph
    CemeCon AG, Adenauerstr. 20 A4, D-52146 Wűrselen, Germany.
    Mesic, Biljana
    CemeCon AG, Adenauerstr. 20 A4, D-52146 Wűrselen, Germany.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Effects of substrate rotation during AlSi-HiPIMS/Ti-DCMS co-sputtering growth of TiAlSiN coatings on phase content, microstructure, and mechanical properties2023In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 453, article id 128986Article in journal (Refereed)
    Abstract [en]

    A combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique is used to deposit Ti0.6Al0.32Si0.08N films with 1-fold substrate table rotation. Layers are grown at two different substrate-target separations, two different rotational speeds, and with different values of substrate bias. The aim is to study the role of (1) overlap between ion and neutral fluxes generated from HiPIMS and DCMS sources, respectively, and (2) the subplantation range of low-mass ions. Results from X-ray diffractometry highlight the necessity of flux intermixing in the formation of the metastable B1-structured TiAlSiN solid solutions. All films grown at short target-to-substrate distance contain the hexagonal AlN phase, as there is essentially no overlap between HiPIMS and DCMS fluxes, thus the Al+ and Si+ subplantation is very limited. Under conditions of high flux intermixing corresponding to larger target-to-substrate distance, no w-AlN forms irrespective of rotational speed (1 or 3 rpm) and bias amplitude (120 or 480 V), indicating that the role of Al+/Si+ and Ti flux overlap is crucial for the phase formation during film growth by HiPIMS/DCMS with substrate rotation. This conclusion is further supported by the fact that the reduction of the bilayer thickness with increasing the target-to-substrate distance (hence increasing flux overlap) is larger for films grown with higher amplitude of the substrate bias, indicative of more efficient Al+/Si+ subplantation into the c-TiN phase. Single-phase films with the hardness close to that of layers grown with stationary substrate table can be achieved, however, at the expense of higher compressive stress.

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  • 34. Order onlineBuy this publication >>
    Hussain, Mushtaque
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Synthesis, Characterization and Applications of Metal Oxide Nanostructures2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of nanotechnology is to build self-powered nanosystems that are ultrasmall in size, exhibit super sensitivity, extraordinary multi functionality, and extremely low power consumption. As we all know that 21st century has brought two most important challenges for us. One is energy shortage and the other is global warming. Now to overcome these challenges, it is highly desirable to develop nanotechnology that harvests energy from the environment to fabricate self-power and low-carbon nanodevices. Therefore a self-power nanosystem that harvests its operating energy from the environment is an attractive proposition. This is also feasible for nanodevices owing to their extremely low power consumption. One advantageous approach towards harvesting energy from the environment is the utilization of semiconducting piezoelectric materials, which facilitate the conversion of mechanical energy into electrical energy. Among many piezoelectric materials ZnO has the rare attribute of possessing both piezoelectric and semiconducting properties. But most applications of ZnO utilize either the semiconducting or piezoelectric property, and now it’s time to fully employ the coupled semiconducting-piezoelectric properties to form  the basis for electromechanically coupled nanodevices. Since wurtzite zinc oxide (ZnO) is structurally noncentral symmetric and has the highest piezoelectric tensor among tetrahedrally bonded semiconductors, therefore it becomes a promising candidate for energy harvesting applications. ZnO is relatively biosafe and biocompatible as well, so it can be used at large scale without any harm to the living environment.

    The synthesis of another transition metal oxide known as Co3O4 is also important due to its potential usage in the material science, physics and chemistry fields. Co3O4 has been studied extensively due to low cost, low toxicity, the most naturally abundant, high surface area, good redox, easily tunable surface and structural properties. These significant properties enable Co3O4 fruitful for developing variety of nanodevices. Co3O4 nanostructures have been focused considerably in the past decade due to their high electro-chemical performance, which is essential for developing highly sensitive sensor devices.

    I started my work with the synthesis of ZnO nanostructures with a focus to improve the amount of harvested energy by utilizing oxygen plasma treatment. Then I grow ZnO nanorods on different flexible substrates, in order to observe the effect of substrate on the amount of harvested energy. After that I worked on understanding the mechanism and causes of variation in the resulting output potential generated from ZnO nanorods. My next target belongs to an innovative approach in which AFM tip decorated with ZnO nanorods was utilized to improve the output energy. Then I investigated Co3O4 nanostructures though the effect of anions and utilized one of the nanostructure to develop a fast and reliable pH sensor. Finally to take the advantage of higher degree of redox chemistry of NiCo0O4 compared to the single phase of nickel oxide and cobalt oxide, a sensitive glucose sensor is developed by immobilizing glucose oxidase.

    However, there were problems with the mechanical robustness, lifetime, output stability and environmental adaptability of such devices, therefore more work is going on to find out new ways and means in order to improve the performance of fabricated nanogenerators and sensors.

    List of papers
    1. The improved piezoelectric properties of ZnO nanorods with oxygen plasma treatment on the single layer graphene coated polymer substrate
    Open this publication in new window or tab >>The improved piezoelectric properties of ZnO nanorods with oxygen plasma treatment on the single layer graphene coated polymer substrate
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    2014 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 211, no 2, p. 455-459Article in journal (Refereed) Published
    Abstract [en]

    The step towards the fabrication of nanodevices with improved performance is of high demand; therefore, in this study, oxygen plasma treated ZnO nanorods based piezoelectric nanogenerator is developed on the single layer graphene coated PET flexible polymer substrate. ZnO nanorods on the single layer graphene are grown by hydrothermal growth method and the structural study is carried out by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The piezoelectric properties of ZnO nanorods with and without plasma treatment were investigated by atomic force microscopy (AFM). The oxygen plasma treated sample of ZnO nanorods showed significant increase in the piezoelectric potential which could be due to the decrease in the defects levels in the ZnO and also increase in the mechanical properties of ZnO nanorods. Furthermore X-ray photoelectron spectroscopy (XPS) confirms that the filling of vacancies by oxygen in the matrix of ZnO using oxygen plasma treatment has gave an enhanced piezoelectric potential compared to the sample of ZnO nanorods not treated with oxygen plasma. In addition to XPS experiment, cathodoluminescence (CL) technique was used for the determination of defect level in the ZnO nanorods after the treatment of oxygen plasma and the obtained information supported the XPS data of oxygen plasma treatment sample by showing the decreased level of defect levels in the prepared sample. From the XPS and CL studies, it is observed that the defect level has significant influence on the piezoelectric potential of the ZnO nanostructures.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlag, 2014
    Keywords
    piezoelectric nanogenerator; plasma treatment; single layer graphene; zinc oxide
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105762 (URN)10.1002/pssa.201300330 (DOI)000332000500030 ()
    Available from: 2014-04-07 Created: 2014-04-04 Last updated: 2024-01-08
    2. The effect of oxygen-plasma treatment on the mechanical andpiezoelectrical properties of ZnO nanorods
    Open this publication in new window or tab >>The effect of oxygen-plasma treatment on the mechanical andpiezoelectrical properties of ZnO nanorods
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    2014 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 608, p. 235-238Article in journal (Refereed) Published
    Abstract [en]

    We have studied the effect of oxygen plasma treatment on piezoelectric response and on the mechanical stability of ZnO nanorods synthesized on FTO by using ACG method. XRD and SEM techniques have shown highly dense and uniformly distributed nanorods. The piezoelectric properties and mechanical stability of as-grown and oxygen plasma treated samples were investigated by using nanoindentation technique. The comparison of load–displacement curves showed that the oxygen plasma treated samples are much stiffer and show higher generated piezo-voltage. This study demonstrates that the oxygenplasma treatment is a good option to fabricate reliable and efficient nanodevices for enhanced generation of piezoelectricity.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-108547 (URN)10.1016/j.cplett.2014.06.018 (DOI)000340202600042 ()
    Available from: 2014-06-30 Created: 2014-06-30 Last updated: 2024-01-08
    3. Comparative Study of Energy Harvesting from ZnO Nanorods Using Different Flexible Substrates
    Open this publication in new window or tab >>Comparative Study of Energy Harvesting from ZnO Nanorods Using Different Flexible Substrates
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    2014 (English)In: Energy Harvesting and Systems, ISSN 2329-8774, Vol. 1, no 1-2, p. 19-26Article in journal (Refereed) Published
    Abstract [en]

    The step toward the fabrication of nanodevices with low cost and improved performance is of high demand; therefore, in the present study, different flexible substrates like common paper, textile fabric, plastic and aluminum foil have been utilized to harvest electrical energy. ZnO nanorods (NRs) were grown by using lowtemperature aqueous chemical growth method. The obtained ZnO NRs were highly dense, well aligned, uniformly distributed over the substrates and exhibited good crystal quality. The structural study was carried out by using X-ray powder diffraction and scanning electron microscopy. The piezoelectric properties of ZnO NRs were investigated by the help of an atomic force microscope using contact mode. The measurements of generated piezoelectricity were around 16.2 mV, 23.2 mV, 38.5 mV and 43.3 mV for common paper, textile fabric, plastic and aluminum foil, respectively. This investigation is an important step in order to study the effect of different substrates influencing the magnitude of the output voltage under identical growth and measurement conditions. We expect that this study will help identify the most suitable flexible substrate for harvesting energy. It also offers a promising alternative powering source for the next generation nanodevices using non-conventional substrates like aluminum foil. Moreover, the use of aluminum foil as flexible and low cost substrate may pave the way to develop devices in different fields including energy harvesting.

    Place, publisher, year, edition, pages
    Walter de Gruyter, 2014
    Keywords
    ZnO nanorods, flexible substrates, aqueous chemical growth, atomic force microscope
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-108226 (URN)10.1515/ehs-2013-0025 (DOI)
    Available from: 2014-06-26 Created: 2014-06-26 Last updated: 2024-01-08Bibliographically approved
    4. Use of ZnO nanorods grown AFM tip in the architecture of piezoelectric nanogenerator
    Open this publication in new window or tab >>Use of ZnO nanorods grown AFM tip in the architecture of piezoelectric nanogenerator