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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.

  • 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.

  • 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.
    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: 2018-05-15
    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
    Show others...
    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: 2018-05-15
    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
    Show others...
    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: 2018-08-16Bibliographically approved
  • 9.
    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.

  • 10.
    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.

  • 11.
    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

  • 12.
    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.

  • 13.
    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.

  • 14.
    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: 2018-04-25Bibliographically 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
  • 15.
    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
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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
    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
  • 16.
    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: 2018-01-03
    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: 2018-01-03Bibliographically 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, 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: 2015-03-09Bibliographically 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: 2017-12-06Bibliographically 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: 2017-12-06Bibliographically 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, ISSN 2158-3226, 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: 2019-05-07Bibliographically 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: 2014-09-18Bibliographically approved
  • 17.
    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, 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: 2019-06-28
  • 18.
    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.

  • 19.
    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
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    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
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    (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
    Show others...
    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
  • 20.
    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.

  • 21.
    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%.

  • 22.
    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: 2017-12-05
    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: 2017-12-05
    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: 2018-02-27Bibliographically 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
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    2014 (English)In: Micro & Nano Letters, ISSN 1750-0443, E-ISSN 1750-0443, Vol. 9, no 8, p. 539-543Article in journal (Refereed) Published
    Abstract [en]

    The piezoelectric potential output has been studied using a ZnO nanorods (NRs) grown atomic force microscope (AFM) tip in lieu of the normally used AFM tip. The ZnO NRs were synthesised on the AFM tip and on the fluorine-doped tin oxide (FTO) glass substrate using the aqueous chemical growth method. The as-grown ZnO NRs were highly dense, well aligned and uniform both on the tip and on the substrate. The structural study was performed using X-ray diffraction and scanning electron microscopy techniques. The piezoelectric properties of as-grown ZnO NRs were investigated using an AFM in contact mode. In comparison to the AFM tip without ZnO NRs, extra positive voltage peaks were observed when the AFM tip with ZnO NRs was used. The pair of ZnO NRs on the AFM tip and on the FTO glass substrate together worked as two oppositely gliding walls (composed of ZnO NRs) and showed an enhancement in the amount of the harvested energy as much as eight times. This approach demonstrates that the use of the AFM tip with ZnO NRs is not only a good alternative to improve the design of nanogenerators to obtain an enhanced amount of harvested energy but is also simple, reliable and cost-effective.

    National Category
    Physical Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-108893 (URN)10.1049/mnl.2014.0237 (DOI)000341502400012 ()
    Available from: 2014-07-11 Created: 2014-07-11 Last updated: 2017-12-05Bibliographically approved
    5. Effect of anions on the morphology of Co3O4 nanostructures grown by hydrothermal method and their pH sensing application
    Open this publication in new window or tab >>Effect of anions on the morphology of Co3O4 nanostructures grown by hydrothermal method and their pH sensing application
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    2014 (English)In: Journal of Electroanalytical Chemistry, ISSN 1572-6657, Vol. 717-718, p. 78-82Article in journal (Refereed) Published
    Abstract [en]

    A fast, reliable, accurate, precise and sensitive pH sensor device is highly demanding for the monitoring of pH in biological, clinical and food industry samples. In this research work, the effect of anions on the morphology of cobalt oxide (Co3O4) nanostructures is investigated using low temperature chemical approach for the growth. Different anions have shown visible effect on the morphology of Co3O4 nanostructures. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy techniques were used for the material characterization. This study has shown highly dense, uniform and good crystal quality of fabricated Co3O4 nanostructures. The nanostructures obtained from the cobalt chloride were used for the development of potentiometric pH sensor electrode. The pH sensor electrode showed excellent linearity and close to Nernstian response for the pH range of 3-13 with a sensitivity of -58.45 mV/pH. Moreover, the proposed sensor showed a fast response time of 53 s, and acceptable reducibility and repeatability. The highly sensitive and a fast time response of the proposed sensor device indicate its potential application for the monitoring of pH from real samples including biological fluids.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Anion effect; Cobalt oxide nanostructures; Morphology; pH sensor; Potentiometric response
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-106984 (URN)10.1016/j.jelechem.2014.01.011 (DOI)000335112200011 ()
    Available from: 2014-06-04 Created: 2014-06-02 Last updated: 2014-10-27Bibliographically approved
    6. Synthesis of Three Dimensional Nickel Cobalt Oxide Nanoneedles on Nickel Foam, Their Characterization and Glucose Sensing Application
    Open this publication in new window or tab >>Synthesis of Three Dimensional Nickel Cobalt Oxide Nanoneedles on Nickel Foam, Their Characterization and Glucose Sensing Application
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    2014 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 14, no 3, p. 5415-5425Article in journal (Refereed) Published
    Abstract [en]

    In the present work, NiCo2O4 nanostructures are fabricated in three dimensions (3D) on nickel foam by the hydrothermal method. The nanomaterial was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The nanostructures exhibit nanoneedle-like morphology grown in 3D with good crystalline quality. The nanomaterial is composed of nickel, cobalt and oxygen atoms. By using the favorable porosity of the nanomaterial and the substrate itself, a sensitive glucose sensor is proposed by immobilizing glucose oxidase. The presented glucose sensor has shown linear response over a wide range of glucose concentrations from 0.005 mM to 15 mM with a sensitivity of 91.34 mV/decade and a fast response time of less than 10 s. The NiCo2O4 nanostructures-based glucose sensor has shown excellent reproducibility, repeatability and stability. The sensor showed negligible response to the normal concentrations of common interferents with glucose sensing, including uric acid, dopamine and ascorbic acid. All these favorable advantages of the fabricated glucose sensor suggest that it may have high potential for the determination of glucose in biological samples, food and other related areas.

    Place, publisher, year, edition, pages
    Basel, Switzerland: MDPI, 2014
    Keywords
    nickel cobalt oxide nanostructures; nickel foam; glucose sensor; potentiometric method
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-108230 (URN)10.3390/s140305415 (DOI)000336783300082 ()
    Available from: 2014-06-26 Created: 2014-06-26 Last updated: 2017-12-05Bibliographically approved
  • 23.
    Jiang, Jie
    et al.
    National University of Singapore .
    Li, Xiaomin
    WinTech Nano-Technology Services Pte. Ltd, Singapore.
    Mak, Wing Cheung
    National University of Singapore .
    Trau, Dieter
    National University of Singapore .
    Integrated direct DNA/protein patterning and microfabrication by focused ion beam milling2008In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 20, no 9, p. 1636-1643Article in journal (Refereed)
    Abstract [en]

    Single and binary component patterning and integrated microfabrication of biomolecules, such as DNA and proteins, can be achieved by focused ion-beam (FIB) biolithography. Well-defined micropatterns are obtained by FIB milling on biomolecules immobilized on SiO2 wafers and protected by a thin Au film. The retention of biofunctionality is excellent (68–90%) and a feature size of down to 500 nm can be achieved for the patterns without significant loss of functionality.

  • 24.
    Junaid, Muhammad
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chen, Yen-Ting
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Effects of N2 Partial Pressure on Growth, Structure, and Optical Properties of GaN Nanorods Deposited by Liquid-Target Reactive Magnetron Sputter Epitaxy2018In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 4, article id 223Article in journal (Other academic)
    Abstract [en]

    GaN nanorods, essentially free from crystal defects and exhibiting very sharp band-edge luminescence, have been grown by reactive direct-current magnetron sputter epitaxy onto Si (111) substrates at a low working pressure of 5 mTorr. Upon diluting the reactive N2 working gas with a small amount of Ar (0.5 mTorr), we observed an increase in the nanorod aspect ratio from 8 to ~35, a decrease in the average diameter from 74 to 35 nm, and a two-fold increase in nanorod density. With further dilution (Ar = 2.5 mTorr), the aspect ratio decreased to 14, while the diameter increased to 60 nm and the nanorod density increased to a maximum of 2.4 × 109 cm−2. Yet, lower N2 partial pressures eventually led to the growth of continuous GaN films. The observed morphological dependence on N2 partial pressure is explained by a change from N-rich to Ga-rich growth conditions, combined with reduced GaN-poisoning of the Ga-target as the N2 gas pressure is reduced. Nanorods grown at 2.5 mTorr N2 partial pressure exhibited a high intensity 4 K photoluminescence neutral donor bound exciton transitions (D0XA) peak at ~3.479 eV with a full-width-at-half-maximum of 1.7 meV. High-resolution transmission electron microscopy corroborated the excellent crystalline quality of the nanorods.

  • 25.
    Kalered, Emil
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Quantum chemical studies of deposition and catalytic surface reactions2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Quantum chemical calculations have been used to model chemical reactions in epitaxial growth of silicon carbide by chemical vapor deposition (CVD) processes and to study heterogeneous catalytic reactions for methanol synthesis. CVD is a common method to produce high-quality materials and e.g. thin films in the semiconductor industry, and one of the many usages of methanol is as a promising future renewable and sustainable energy carrier. To optimize the chemical processes it is essential to understand the reaction mechanisms. A comprehensive theoretical model for the process is therefore desired in order to be able to explore various variables that are difficult to investigate in situ. In this thesis reaction paths and reaction energies are computed using quantum chemical calculations. The quantum-chemical results can subsequently be used as input for thermodynamic, kinetic and computational fluid dynamics modelling in order to obtain data directly comparable with the experimental observations.

    For the CVD process, the effect of halogen addition to the gas mixture is studied by modelling the adsorption and diffusion of SiH2, SiCl2 and SiBr2 on the (0001̅) 4H-SiC surface. SiH2 was found to bind strongest to the surface and SiBr2 binds slightly stronger than the SiCl2 molecule. The diffusion barrier is shown to be lower for SiH2 than for SiBr2 and SiCl2 which have similar barriers. SiBr2 and SiCl2 are found to have similar physisorption energies and bind stronger than the SiH2 molecule. Gibbs free-energy calculations also indicate that the SiC surface is not fully hydrogen terminated at CVD conditions since missing-neighboring pair of surface hydrogens is found to be common. Calculations for the (0001) surface show that SiCl, SiCl2, SiHCl, SiH, and SiH2 likely adsorb on a methylene site, but the processes are thermodynamically less favorable than their reverse reactions. However, the adsorbed products may be stabilized by subsequent surface reactions to form a larger structure. The formation of these larger structures is found to be fast enough to compete with the desorption processes. Also the Gibbs free energies for adsorption of Si atoms, SiX, SiX2, and SiHX where X is F or Br are presented. Adsorption of Si atoms is shown to be the most thermodynamically favorable reaction followed by SiX, SiHX, and SiX2, X being a halide. The results in this study suggest that the major Si contributors in the SiC–CVD process are Si atoms, SiX and SiH.

    Methanol can be synthesized from gaseous carbon dioxide and hydrogen using solid metal-metal oxide mixtures acting as heterogeneous catalysts. Since a large surface area of the catalyst enhances the speed of the heterogeneous reaction, the use of nanoparticles (NP) is expected to be advantageous due to the NPs’ large area to surface ratio. The plasma-induced creation of copper NPs is investigated. One important element during particle growth is the charging process where the variation of the work function (W) with particle size is a key quantity, and the variation becomes increasingly pronounced at smaller NP sizes. The work functions are computed for a set of NP charge numbers, sizes and shapes, using copper as a case study. A derived analytical expression for W is shown to give quite accurate estimates provided that the diameter of the NP is larger than about a nanometer and that the NP has relaxed to close to a spherical shape. For smaller sizes W deviates from the approximative expression, and also depends on the charge number. Some consequences of these results for NP charging process are outlined.

    Key reaction steps in the methanol synthesis reaction mechanism using a Cu/ZrO2 nanoparticle catalyst is investigated. Two different reaction paths for conversion of CO2 to CO is studied. The two paths result in the same complete reaction 2 CO2 → 2 CO + O2 where ZrO2 (s) acts as a catalyst. The highest activation energies are significantly lower compared to that of the gas phase reaction. The presence of oxygen vacancies at the surface appear to be decisive for the catalytic process to be effective. Studies of the reaction kinetics show that when oxygen vacancies are present on the ZrO2 surface, carbon monoxide is produced within a microsecond. The IR spectra of CO2 and H2 interacting with ZrO2 and Cu under conditions that correspond to the catalyzed CH3OH production process is also studied experimentally and compared to results from the theoretical computations. Surface structures and gas-phase molecules are identified through the spectral lines by matching them to specific vibrational modes from the literature and from the new computational results. Several surface structures are verified and can be used to pin point surface structures in the reaction path. This gives important information that help decipher how the reaction mechanism of the CO2 conversion and ultimately may aid to improve the methanol synthesis process.

    List of papers
    1. Adsorption and surface diffusion of silicon growth species in silicon carbide chemical vapour deposition processes studied by quantum-chemical computations
    Open this publication in new window or tab >>Adsorption and surface diffusion of silicon growth species in silicon carbide chemical vapour deposition processes studied by quantum-chemical computations
    2013 (English)In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 132, no 12Article in journal (Refereed) Published
    Abstract [en]

    The effect chlorine addition to the gas mixture has on the surface chemistry in the chemical vapour deposition (CVD) process for silicon carbide (SiC) epitaxial layers is studied by quantum-chemical calculations of the adsorption and diffusion of SiH2 and SiCl2 on the (000-1) 4H–SiC surface. SiH2 was found to bind more strongly to the surface than SiCl2 by approximately 100 kJ mol−1 and to have a 50 kJ mol−1 lower energy barrier for diffusion on the fully hydrogen-terminated surface. On a bare SiC surface, without hydrogen termination, the SiCl2 molecule has a somewhat lower energy barrier for diffusion. SiCl2 is found to require a higher activation energy for desorption once chemisorbed, compared to the SiH2 molecule. Gibbs free energy calculations also indicate that the SiC surface may not be fully hydrogen terminated at CVD conditions since missing neighbouring pair of surface hydrogens is found to be a likely type of defect on a hydrogen-terminated SiC surface.

    Place, publisher, year, edition, pages
    Springer Verlag (Germany), 2013
    Keywords
    Quantum-chemical calculations, Density functional theory (DFT), B3LYP, Chemical vapour deposition (CVD), Silicon carbide (SiC), SiCl2, SiH2, Surface reactions, Adsorption, Reaction path, Activation energy, Diffusion, Hydrogen termination
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-100478 (URN)10.1007/s00214-013-1403-3 (DOI)000325724400001 ()
    Available from: 2013-11-08 Created: 2013-11-08 Last updated: 2018-06-19Bibliographically approved
    2. Brominated chemistry for chemical vapor deposition of electronic grade SiC
    Open this publication in new window or tab >>Brominated chemistry for chemical vapor deposition of electronic grade SiC
    Show others...
    2015 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 3, p. 793-801Article in journal (Refereed) Published
    Abstract [en]

    Chlorinated chemical vapor deposition (CVD) chemistry for growth of homoepitaxial layers of silicon carbide (SiC) has paved the way for very thick epitaxial layers in short deposition time as well as novel crystal growth processes for SiC. Here, we explore the possibility to also use a brominated chemistry for SiC CVD by using HBr as additive to the standard SiC CVD precursors. We find that brominated chemistry leads to the same high material quality and control of material properties during deposition as chlorinated chemistry and that the growth rate is on average 10 % higher for a brominated chemistry compared to chlorinated chemistry. Brominated and chlorinated SiC CVD also show very similar gas phase chemistries in thermochemical modelling. This study thus argues that brominated chemistry is a strong alternative for SiC CVD since the deposition rate can be increased with preserved material quality. The thermochemical modelling also suggest that the currently used chemical mechanism for halogenated SiC CVD might need to be revised.

    National Category
    Chemical Sciences Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-111075 (URN)10.1021/acs.chemmater.5b00074 (DOI)000349934500016 ()
    Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2018-06-19Bibliographically approved
    3. Growth Mechanism of SiC Chemical Vapor Deposition: Adsorption and Surface Reactions of Active Si Species
    Open this publication in new window or tab >>Growth Mechanism of SiC Chemical Vapor Deposition: Adsorption and Surface Reactions of Active Si Species
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    2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 1, p. 648-661Article in journal (Refereed) Published
    Abstract [en]

    Silicon carbide is a wide bandgap semiconductor ideally suitable for high temperature and high power applications. An active SiC layer is usually fabricated using halide-assisted chemical vapor deposition (CVD). In this work, we use quantum chemical density functional theory (B3LYP and M06-2X) and transition state theory to study adsorptions of active Si species in the CVD process on both the Si face and the C face of 4H-SiC. We show that adsorptions of SiCl, SiCl2, SiHCl, SiH, and SiH2 on the Si face likely occur on a methylene site, CH2(ads), but the processes are thermodynamically less favorable than their reverse or desorptions. Nevertheless, the adsorbed products become stabilized with the help of subsequent surface reactions to form a larger cluster. These cluster formation reactions happen with rates that are fast enough to compete with the desorption processes. On the C face, the adsorptions likely occur on a surface site terminated by a dangling bond, *(ads), and produce the products which are thermodynamically stable. Lastly, we present the Gibbs free energies of adsorptions of Si atoms, SiX, SiX2, and SiHX, for X being F and Br. Adsorptions of Si atoms are shown to be the most thermodynamically favorable among all the species in the study. Among the halide-containing species, the Gibbs free energies (ARG) from smallest to largest are observed in the adsorptions of SiX, SiHX, and SiX2, for X being the halides. The results in this study suggest that the major Si contributors in the SiC CVD process are Si atoms, SiX (for X being the halide) and SiH.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2018
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-144885 (URN)10.1021/acs.jpcc.7b10751 (DOI)000422814200069 ()
    Note

    Funding Agencies|Swedish Foundation for Strategic Research from Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Swedish Research Council (VR) [2016-05137_4]

    Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2018-06-19
    4. On the work function and the charging of small (r <= 5 nm) nanoparticles in plasmas
    Open this publication in new window or tab >>On the work function and the charging of small (r <= 5 nm) nanoparticles in plasmas
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    2017 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 1, article id 013702Article in journal (Refereed) Published
    Abstract [en]

    The growth of nanoparticles (NPs) in plasmas is an attractive technique where improved theoretical understanding is needed for quantitative modeling. The variation of the work function W with size for small NPs, r(NP) amp;lt;= 5 nm, is a key quantity for modeling of three NP charging processes that become increasingly important at a smaller size: electron field emission, thermionic electron emission, and electron impact detachment. Here we report the theoretical values of the work function in this size range. Density functional theory is used to calculate the work functions for a set of NP charge numbers, sizes, and shapes, using copper for a case study. An analytical approximation is shown to give quite accurate work functions provided that r(NP) amp;gt; 0.4 nm, i.e., consisting of about amp;gt; 20 atoms, and provided also that the NPs have relaxed close to spherical shape. For smaller sizes, W deviates from the approximation, and also depends on the charge number. Some consequences of these results for nanoparticle charging are outlined. In particular, a decrease in W for NP radius below about 1 nm has fundamental consequences for their charge in a plasma environment, and thereby on the important processes of NP nucleation, early growth, and agglomeration. Published by AIP Publishing.

    Place, publisher, year, edition, pages
    AMER INST PHYSICS, 2017
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-136218 (URN)10.1063/1.4973443 (DOI)000395395100092 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg foundation (KAW) [2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Available from: 2017-03-31 Created: 2017-03-31 Last updated: 2018-06-19
  • 26.
    Karlsson, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Transmission Electron Microscopy of 2D Materials: Structure and Surface Properties2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    During recent years, new types of materials have been discovered with unique properties. One family of such materials are two-dimensional materials, which include graphene and MXene. These materials are stronger, more flexible, and have higher conductivity than other materials. As such they are highly interesting for new applications, e.g. specialized in vivo drug delivery systems, hydrogen storage, or as replacements of common materials in e.g. batteries, bulletproof clothing, and sensors. The list of potential applications is long for these new materials.

    As these materials are almost entirely made up of surfaces, their properties are strongly influenced by interaction between their surfaces, as well as with molecules or adatoms attached to the surfaces (surface groups). This interaction can change the materials and their properties, and it is therefore imperative to understand the underlying mechanisms. Surface groups on two-dimensional materials can be studied by Transmission Electron Microscopy (TEM), where high energy electrons are transmitted through a sample and the resulting image is recorded. However, the high energy needed to get enough resolution to observe single atoms damages the sample and limits the type of materials which can be analyzed. Lowering the electron energy decreases the damage, but the image resolution at such conditions is severely limited by inherent imperfections (aberrations) in the TEM. During the last years, new TEM models have been developed which employ a low acceleration voltage together with aberration correction, enabling imaging at the atomic scale without damaging the samples. These aberration-corrected TEMs are important tools in understanding the structure and chemistry of two-dimensional materials.

    In this thesis the two-dimensional materials graphene and Ti3C2Tx MXene have been investigated by low-voltage, aberration-corrected (scanning) TEM. High temperature annealing of graphene covered by residues from the synthesis is studied, as well as the structure and surface groups on single and double Ti3C2Tx MXene. These results are important contributions to the understanding of this class of materials and how their properties can be controlled.

    List of papers
    1. Residue reduction and intersurface interaction on single graphene sheets
    Open this publication in new window or tab >>Residue reduction and intersurface interaction on single graphene sheets
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    2016 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 100, p. 345-350Article in journal (Refereed) Published
    Abstract [en]

    Large regions of pristine graphene are essential to applications which rely on the ideal graphene properties. Common methods for transferring chemical vapour deposition grown graphene to suitable substrates leaves metal oxide particles and poly(methyl methacrylate) (PMMA) residues on opposing surfaces, which degrade the properties. A common method to reduce the residues include annealing in vacuum or in argon, however, residues remain on the graphene sheet. The present investigation reports on the metal oxide particle ripening and PMMA decomposition on a single graphene sheet during in-situ annealing up to 1300 degrees C in a transmission electron microscope. It is shown that the PMMA residues are increasingly reduced at elevated temperatures although the reduction is strongly correlated to the metal oxide particle coverage on the opposing graphene surface. This is shown to occur as a consequence of an electrostatic interaction between the residues and that this prevents the establishment of large clean areas. (C) 2016 Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    Pergamon Press, 2016
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-126123 (URN)10.1016/j.carbon.2016.01.007 (DOI)000369961400040 ()
    Note

    Funding Agencies|Swedish Research Council [621-2012-4359, 622-2008-405, 642-2013-8020]; Olle Engkvist foundation; Knut and Alice Wallenbergs Foundation; European Research Council [258509]; IBS Korea [IBS-RO11-D1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]

    Available from: 2016-03-15 Created: 2016-03-15 Last updated: 2017-11-30Bibliographically approved
    2. Atomically Resolved Structural and Chemical Investigation of Single MXene Sheets
    Open this publication in new window or tab >>Atomically Resolved Structural and Chemical Investigation of Single MXene Sheets
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    2015 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 8, p. 4955-4960Article in journal (Refereed) Published
    Abstract [en]

    The properties of two-dimensional (2D) materials depend strongly on the chemical and electrochemical activity of their surfaces. MXene, one of the most recent additions to 2D materials, shows great promise as an energy storage material. In the present investigation, the chemical and structural properties of individual Ti3C2 MXene sheets with associated surface groups are investigated at the atomic level by aberration corrected STEM-EELS. The MXene sheets are shown to exhibit a nonuniform coverage of O-based surface groups which locally affect the chemistry. Additionally, native point defects which are proposed to affect the local surface chemistry, such as oxidized titanium adatoms (TiOx), are identified and found to be mobile.

    Keywords
    MXene, Ti3C2Tx, Aberration corrected STEM, Surface Chemistry, Surface
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-120927 (URN)10.1021/acs.nanolett.5b00737 (DOI)000359613700017 ()26177010 (PubMedID)
    Available from: 2015-08-31 Created: 2015-08-31 Last updated: 2017-12-04Bibliographically approved
  • 27.
    Khan, Azam
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Analysis of the piezoelectric and current transport properties of zinc oxide nanostructures grown on fiber2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It seems that nowadays the world is becoming as a small village due to the advancement in communication devices technology. These devices are playing an important role in the wellbeing of our life as almost each and every person is utilizing at least one of these devices. These devices consume energy and with our increased use of technology, we are faced  with energy crises. Therefore, the research community is keen in trying to explore alternative resources. One possibility is to search for the alternative resources from our environment. The attempt in this thesis was to utilize the piezoelectric properties by harvesting electrical energy from nanostructures. By utilizing the piezoelectric property of some materials, mechanical energy can be harvested as electrical output. It is worth mention that the ambient mechanical energy is the most available source of energy around us. Hence it is of interest to utilize it to develop future smart devices having the self-powered property. In this connection various experimental and mathematical techniques have been utilized for achieving this target.

    In this thesis zinc oxide (ZnO) nanostructures grown on textile substrates were the material. The use of textile as substrate is quite unique property of the presented work. Since textile is an essential and fundamental component of our everyday lives, therefore the use of textile as substrate can pave the way for the fabrication of novel self-powered devices. As in comparison with conventional and expensive substrates textile is very economical, lightweight, highly flexible, recyclable, reproducible, disposable, wearable and washable.

    I started my research work by integrating ZnO nanorods based nanogenerator on conductive textile fiber for the analysis of piezoelectric properties of ZnO nanorods. The acceptance of my work among the research community encouraged me to continue with it in order to improve the performance of the fabricated device. It is well known that piezoelectricity is a linear electromechanical coupling of the material in which mechanical energy is converted into electrical energy. Therefore, the piezoelectric properties of ZnO nanorods were investigated with regard to different physical parameters. In the electromechanical phenomena the analysis of the direct and the converse piezoelectric effect is also critical if conductive textile is used as a substrate. Therefore analysis of the direct and the converse piezoelectric effect was performed for ZnO nanowires grown on conductive textile fiber by using the nanoindentation method.

    Since the morphology of ZnO nanostructures can have an influence on the piezoelectric properties, the energy harvesting properties of ZnO nanoflowers were investigated and the achieved results confirmed that morphology has a strong influence on the piezoelectric properties. In addition, since there is an interest to generate a direct current (DC) piezoelectricity, a Schottky junction fabricated to one side of the nanogenerator material is needed. Therefore, ZnO nanorods based Schottky diode (Cu/ZnO) on textile fabric was fabricated and investigated. Moreover, frequency dependence electrical characterization was performed for analysis of current-transport properties of another Schottky diode (Au/ZnO) for understanding the carrier flow at the interface of the metal-semiconductor. Nevertheless, the consistency and stability of the constructed devices (ZnO nanogenerators and Schottky diodes) need some additional work to overcome these problems to achieve commercial realization of these devices in the future.

    List of papers
    1. Piezoelectric nanogenerator based on zinc oxide nanorods grown on textile cotton fabric
    Open this publication in new window or tab >>Piezoelectric nanogenerator based on zinc oxide nanorods grown on textile cotton fabric
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    2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 19Article in journal (Refereed) Published
    Abstract [en]

    This investigation explores piezoelectricity generation from ZnO nanorods, which were grown on silver coated textile cotton fabrics using the low temperature aqueous chemical growth method. The morphology and crystal structure studies were carried out by x-ray diffraction, scanning electron microscopic and high resolution transmission electron microscopic techniques, respectively. ZnO nanorods were highly dense, well aligned, uniform in spatial distribution and exhibited good crystal quality. The generation of piezoelectricity from fabricated ZnO nanorods grown on textile cotton fabrics was measured using contact mode atomic force microscopy. The average output voltage generated from ZnO nanorods was measured to be around 9.5 mV. This investigation is an important achievement regarding the piezoelectricity generation on textile cotton fabric substrate. The fabrication of this device provides an alternative approach for a flexible substrate to develop devices for energy harvesting and optoelectronic technology on textiles.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2012
    Keywords
    atomic force microscopy; electric generators; energy harvesting; flexible electronics; II-VI semiconductors; nanofabrication; nanorods; optoelectronic devices; piezoelectric devices; piezoelectricity; scanning electron microscopy; semiconductor growth; transmission electron microscopy; wide band gap semiconductors; X-ray diffraction; zinc compounds
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-87217 (URN)10.1063/1.4766921 (DOI)000311320100070 ()
    Available from: 2013-01-14 Created: 2013-01-14 Last updated: 2017-12-06
    2. Mechanical and piezoelectric properties of zinc oxide nanorods grown on conductive textile fabric as an alternative substrate
    Open this publication in new window or tab >>Mechanical and piezoelectric properties of zinc oxide nanorods grown on conductive textile fabric as an alternative substrate
    2014 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 47, no 34, p. 345102-Article in journal (Refereed) Published
    Abstract [en]

    The present research is devoted to understanding the mechanism and causes of variation in the piezoelectric potential generated from vertically aligned zinc oxide (ZnO) nanorods (NRs), which were grown on a conductive textile fabric as an alternative substrate by using the aqueous chemical growth method. The piezoelectric voltage was harvested from vertically aligned ZnO NRs having different physical parameters by using atomic force microscopy in contact mode and the variation in the generated piezoelectricity was investigated. The generated output potential indicates that different physical parameters such aspect ratio, crystal size and lattice internal crystal strain have a strong influence on the piezoelectric properties of vertically aligned ZnO NRs, which were grown on a textile fabric. Presented results indicate that textiles can be used as an alternative substrate just like the other conventional substrates, because our results are similar/better than many reported works on conventional substrates.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2014
    Keywords
    conductive textile fabric; ZnO nanorods; aqueous chemical growth method; mechanical and piezoelectric properties
    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-110270 (URN)10.1088/0022-3727/47/34/345102 (DOI)000340236700008 ()
    Available from: 2014-09-05 Created: 2014-09-05 Last updated: 2017-12-05Bibliographically approved
    3. Analysis of direct and converse piezoelectric responses from zinc oxide nanowires grown on a conductive fabric
    Open this publication in new window or tab >>Analysis of direct and converse piezoelectric responses from zinc oxide nanowires grown on a conductive fabric
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    2015 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 212, no 3, p. 579-584Article in journal (Refereed) Published
    Abstract [en]

    Single crystalline hexagonal wurtzite zinc oxide nanowires were grown on conductive commercial textile fabric as piezoelectric material. Aqueous chemical growth (ACG) method was used for the synthesis of ZnO nanowires. Field emission surface scanning electron microscopy and X-ray diffraction techniques were used for surface and structural analysis of grown nanowires. The mechanical and piezoelectric properties of the nanowires were investigated by nanoindantation. Piezoelectric potentials up to 0.013 V were measured in response to direct applied loads in the range 0 - 11 mN. Also, a DC voltage was applied for measurement of converse piezoelectric response under a low constant applied force (~5 μN) and the piezoelectric coefficient was found to be 33.2 pm/V. This study performed on commercial conductive textile demonstrates the feasibility to fabricate wearable nanogenerator clothing.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2015
    Keywords
    zinc oxide nanowires; conductive fabric; aqueous chemical growth; piezoelectricity
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-110893 (URN)10.1002/pssa.201431625 (DOI)000351530800015 ()
    Note

    On the day of the defence date of the Ph.D. Thesis, the status of this article was Manuscript.

    Available from: 2014-09-26 Created: 2014-09-26 Last updated: 2018-02-16Bibliographically approved
    4. Harvesting piezoelectric potential from zinc oxide nanoflowers grown on textile fabric substrate
    Open this publication in new window or tab >>Harvesting piezoelectric potential from zinc oxide nanoflowers grown on textile fabric substrate
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    2013 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 7, no 11, p. 980-984Article in journal (Refereed) Published
    Abstract [en]

    ZnO nanoflowers were synthesized on conductive flexible textile fabric substrate by using the simple low-temperature aqueous chemical growth method and were used for piezoelectric energy harvesting source. Structural characterization of ZnO nanoflowers was carried out by using surface scanning electron microscopy and X-ray diffraction. The ZnO nanoflowers are uniformly grown over the entire sample. They are composed of needle-like nanorods, which have hexagonal wurtzite structure with good crystalline quality. The current-voltage characteristics showed good rectifying Schottky behaviour. Contact-mode atomic force microscopy was used for measuring the piezoelectric output potential. The maximum output potential was found to be more than 600 mV and the corresponding current also recorded was near approximate to 650 nA.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlag, 2013
    Keywords
    textiles; aqueous chemical growth; ZnO; nanoflowers; energy harvesting; piezoelectric properties
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-103308 (URN)10.1002/pssr.201308105 (DOI)000328321700011 ()
    Available from: 2014-01-16 Created: 2014-01-16 Last updated: 2017-12-06
    5. Study of transport properties of copper/zinc-oxide-nanorods-based Schottky diode fabricated on textile fabric
    Open this publication in new window or tab >>Study of transport properties of copper/zinc-oxide-nanorods-based Schottky diode fabricated on textile fabric
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    2013 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 28, no 12, p. 125006-Article in journal (Refereed) Published
    Abstract [en]

    In this work, a copper/zinc-oxide (ZnO)-nanorods-based Schottky diode was fabricated on the textile fabric substrate. ZnO nanorods were grown on a silver-coated textile fabric substrate by using the hydrothermal route. Scanning electron microscopy and x-ray diffraction techniques were used for the structural study. The electrical characterization of copper/ZnO-nanorods-based Schottky diodes was investigated by using a semiconductor parameter analyzer and an impedance spectrometer. The current density-voltage (J-V) and capacitance-voltage (C-V) measurements were used to estimate the electrical parameters. The threshold voltage (V-th), ideality factor (eta), barrier height (phi(b)), reverse saturation current density (J(s)), carrier concentration (N-D) and built-in potential (V-bi) were determined by using experimental data and (simulated) curve fitting. This study describes the possible fabrication of electronic and optoelectronic devices on textile fabric substrate with an acceptable performance.

    Place, publisher, year, edition, pages
    Institute of Physics: Hybrid Open Access, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-102717 (URN)10.1088/0268-1242/28/12/125006 (DOI)000327467300012 ()
    Available from: 2013-12-19 Created: 2013-12-19 Last updated: 2018-10-02
    6. Analysis of junction properties of gold-zinc oxide nanorods-based Schottky diode by means of frequency dependent electrical characterization on textile
    Open this publication in new window or tab >>Analysis of junction properties of gold-zinc oxide nanorods-based Schottky diode by means of frequency dependent electrical characterization on textile
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    2014 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 9, p. 3434-3441Article in journal (Refereed) Published
    Abstract [en]

    Present work is an effort to reveal the junction properties of gold/zinc oxide (ZnO) nanorods-based Schottky diode by using the frequency dependent electrical properties. The most important electrical parameters such as conductance, resistance, capacitance, and impedance were studied as function of frequency across the series of AC voltages. Moreover, current density-voltage (J-V) was measured to know the performance of present Schottky diode. The effect of native defects was also studied by using cathodoluminescence spectroscopy measured at different accelerating voltage. The textile substrate was used for the growth of ZnO nanorods by using the aqueous chemical growth method and Schottky diode fabrication. Diode fabrication on textile fabric is a step forward toward the fabrication of electronic devices on nonconventional, economical, soft, light weight, flexible, wearable, washable, recyclable, reproducible, and nontoxic substrate.

    Place, publisher, year, edition, pages
    Springer Verlag (Germany), 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105403 (URN)10.1007/s10853-014-8053-2 (DOI)000331388000016 ()
    Available from: 2014-03-21 Created: 2014-03-21 Last updated: 2018-02-16
  • 28.
    Kumar Yalamanchili, Phani
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Multiscale materials design of hard coatings for improved fracture resistance and thermal stability2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Physical vapor deposited hard coatings comprised of cubic (c) transition metal (TM)-Al-N, and (TM)-Si-N are the current workhorse materials for a large number of metal cutting and wear resistant applications to fight against the extreme conditions of temperature and stress simultaneously. In spite of a high degree of sophistication in terms of material choice and microstructural design, a lower fracture resistance and limited thermal stability of the coatings remains a technological challenge in the field. The lower fracture resistance of the coating is an inherent material property. Limited thermal stability in the TM-Al-N system is associated with the transformation of metastable c -AlN to its stable wurtzite (w)-AlN phase at a temperature above 900 oC resulting an undesirable hardness drop.

    The current work shows how to overcome these challenges by manipulating the coating material at different length scales, i.e. microstructure, crystal and interface structure, and alloy design. The endeavor of multiscale materials design is achieved by converging a deeper material and process knowledge to result specific structural modification over multiple length scales by alloying transition metal nitrides with AlN and SiNx as following.

    Microstructure variation is achieved in ZrN coating by alloying it with SiNx, where the surface segregated SiNx breaks down the columnar structure and evolves a selforganized nanocomposite structure with a hardness variation from 37 ±2 GPa to 26 ±1 GPa. The indentation induced fracture studies reveal crack deflection for the columnar coating, likely along the column boundaries. The crack deflection offers additional energy dissipative mechanisms that make the columnar structured coating more fracture resistant, which is not the case for the nanocomposite coating in spite of its lower hardness.

    Crystal structure of AlN is varied between stable wurtzite structure to metastable cubic structure in the ZrAlN alloy by adapting a multilayer structure and tuning the layer thickness. The multilayer consisting c-AlN layer shows a hardness of 34 ±1 GPa and a twofold enhancement in the critical force to cause an indentation induced surface crack compared to the multilayer containing w-AlN in spite of a lower hardness for the later case. The higher fracture resistance is discovered to be caused by stress- induced transformation of AlN from its metastable cubic structure to its thermodynamically stable wurtzite structure associated with a molar volume expansion of 20% that builds up local compressive stress zones delaying the onset and propagation of the cracks. This is in fact the first experimental data point for the stress-induced transformation toughening in a hard coating.

    The current work also demonstrates a concept of improving the thermal stability of the TM-Al-N by modifying the interface structure between w-AlN and c-TMN. A popular belief in the field is that AlN in its stable wurtzite structure is detrimental to coating hardness, and hence the current material design strategy is to force AlN in metastable cubic phase that confines the application temperature (~ 900 oC). In contrast, here it is shown that the w-AlN offers a high hardness provided if it is grown (semi-)coherent to c-TMN. This is experimentally shown for the multilayer system of TiN/ZrAlN. The interface structure between the c-TiN, c-ZrN and w-AlN is transformed from incoherent to (semi-)coherent structure by tuning the growth conditions under a favorable crystallographic template. Furthermore, the low energy (semi-) coherent interface structure between w-AlN and c- TiN, c- ZrN display a high thermal stability, causing a high and more stable hardness up to an annealing temperature of 1150 oC with a value of 34± 1.5 GPa. This value is 50 % higher compared to the state-of-the-art monolithic and multilayered Ti-Al-N and Zr-Al-N coating containing incoherent w-AlN.

    Finally, an entropy based alloy design concept is explored to form a thermodynamically stable solid solution in the TM-Al-N material system that has a positive enthalpy of mixing. Multi-principal element alloys of (AlTiVCrNb)N are formed in a near ideal cubic solid solution. The high configurational entropy in the alloy is predicted to overcome positive enthalpy of mixing, there by an entropy stabilized solid solution formation is expected at a temperature above 1000 K. However, at elevated temperature, optimization between the minimization of interaction energy and maximization of configurational randomness causes precipitation of AlN in its stable wurtzite structure and the cubic solid solution is only confined between TiN, CrN, VN and NbN that have a low enthalpy of mixing.

    In summary, this work provides technological solutions to the two outstanding issues in the field. A significant enhancement in fracture resistance of the coating is achieved with appropriate material choice and microstructural design by invoking crack deflection and stress induced transformation toughening mechanisms. A remarkable thermal stability enhancement of the TM-Al-N coating is achieved by a new structural archetype consisting c-TMN and thermodynamically stable w-AlN with a low energy (semi-)coherent interface structure.

    List of papers
    1. Structure, deformation and fracture of arc evaporated Zr-Si-N ternary hard films
    Open this publication in new window or tab >>Structure, deformation and fracture of arc evaporated Zr-Si-N ternary hard films
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    2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 1100-1107Article in journal (Refereed) Published
    Abstract [en]

    Zr-Si-N films with varying Si contents were grown on WC-Co substrates with an industrial scale reactive cathodic arc deposition technique. The microstructural changes correlate to variation in mechanical properties with different deformation mechanisms dominating for different structures. Si forms a substitutional solid solution in the cubic ZrN lattice up to 1.8 at. % in a fine columnar structure. Further Si additions results in precipitation of an amorphous (a)-SiNX phase and evolution of a nanocomposite structure (nc ZrN-a SiNX) which has completely suppressed the columnar structure at 6.3 at. % Si. The rotation-induced artificial layering during film growth was used as a marker to visualize the deformation of the film. A dislocation-based homogeneous plastic deformation mechanism dominates the columnar structure, while grain boundary sliding is the active mechanism mediating heterogeneous plastic deformation in the nanocomposite structure. Film hardness increases with increasing Si content in the columnar structure due to an effective solid solution strengthening. The deformation mechanism of localized grain boundary sliding in the nanocomposite structure results in lower hardness. When cracking is induced by indentation, the fine columnar structure exhibits pronounced crack deflection that results in higher fracture resistance compared to the nanocomposite films.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-106760 (URN)10.1016/j.surfcoat.2014.07.024 (DOI)000346895000134 ()
    Available from: 2014-05-21 Created: 2014-05-21 Last updated: 2018-01-03Bibliographically approved
    2. Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening
    Open this publication in new window or tab >>Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening
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    2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 89, p. 22-31Article in journal (Refereed) Published
    Abstract [en]

    Structure and mechanical properties of nanoscale multilayers of ZrN/Zr0.63Al0.37N grown by reactive magnetron sputtering on MgO (0 0 1) substrates at a temperature of 700 degrees C are investigated as a function of the Zr0.63Al0.37N layer thickness. The Zr0.63Al0.37N undergoes in situ chemical segregation into ZrN-rich and AlN-rich domains. The AlN-rich domains undergo transition from cubic to wurtzite crystal structure as a function of Zr0.63Al0.37N layer thickness. Such structural transformation allows systematic variation of hardness as well as fracture resistance of the films. A maximum fracture resistance is achieved for 2 nm thick Zr0.63Al0.37N layers where the AlN-rich domains are epitaxially stabilized in the metastable cubic phase. The metastable cubic-AlN phase undergoes stress-induced transformation to wurtzite-AlN when subjected to indentation, which results in the enhanced fracture resistance. A maximum hardness of 34 GPa is obtained for 10 nm thick Zr0.63Al0.37N layers where the wurtzite-AlN and cubic-ZrN rich domains form semi-coherent interfaces.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Nitride multilayer thin films; Mechanical properties; Fracture toughness
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-118029 (URN)10.1016/j.actamat.2015.01.066 (DOI)000353249100003 ()
    Note

    Funding Agencies|European Unions Erasmus-Mundus graduate school in Material Science and Engineering (DocMASE); Swedish Foundation for Strategic Research (SSF) through the grant Designed Multicomponent Coatings (MultiFilms); Swedish Governmental Agency for Innovation Systems (Vinnova) through the VINN Excellence Centre FunMat; VINNMER Grant [2011-03464]; EU [C/4-EFRE-13/2009/Br]; DFG; federal state government of Saarland [INST 256/298-1 FUGG]

    Available from: 2015-05-21 Created: 2015-05-20 Last updated: 2017-12-04Bibliographically approved
  • 29.
    Mak, Wing Cheung
    et al.
    Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
    Sin, K. K.
    DNA SuperNova Limited, Hong Kong, China.
    Chan, Cangel Pui Yee
    Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China.
    Wong, Ling Wai
    DNA SuperNova Limited, Hong Kong, China.
    Renneberg, Reinhard
    Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
    Biofunctionalized indigo-nanoparticles as biolabels for the generation of precipitated visible signal in immunodipsticks2011In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 26, no 7, p. 3148-3153Article in journal (Refereed)
    Abstract [en]

    A novel class of organic nanoparticles as biolabels that can generate an instant visible signal was applied to immunodipsticks. A new principle for signal generation based on hydrolysis of colourless signal precursor molecules to produce coloured signal molecules followed by signal precipitation and localization was demonstrated. The nanoparticle biolabels were applied to sandwich immunoassays for the detection of mouse immunoglobulin G (M IgG). In the presence of M IgG, a nanoparticle-immunocomplex was formed and bound on the test zone immobilized with goat anti M IgG (Gt α M IgG). A blue line was developed on the test zone upon the addition of a signal developing reagent. An optical signal could be simply assessed using naked eyes or quantified using a reading device. The lowest visible signal that could be observed using naked eyes was found to be 1.25 μg L−1 M IgG. The nanoparticle biolabel also showed a better sensitivity (signal-to-noise ratio) compared with the conventional colloidal gold biolabel. This novel class of organic nanoparticles offers an alternative biolabel system for the development of point-of-care immunodipsticks.

  • 30.
    Mak, Wing Cheung
    et al.
    Hong Kong University of Science and Technology, Hong Kong, China.
    Sum, Ka Wai
    Hong Kong University of Science and Technology, Hong Kong, China.
    Trau, Dieter
    Hong Kong University of Science and Technology, Hong Kong, China.
    Renneberg, Reinhard
    Hong Kong University of Science and Technology, Hong Kong, China.
    Nanoscale surface engineered living cells with extended substrate spectrum2004In: IEE Proceedings - Nanobiotechnology, ISSN 1478-1581, Vol. 151, no 2, p. 67-72Article in journal (Refereed)
    Abstract [en]

    We report on cell surface engineering of living microorganisms by using Layer-by-Layer (LbL) technology to extend the substrate spectrum. The yeast Arxula adeninivorans LS3 (Arxula) was employed as a model organism and biological template. By using LbL technology, Arxula cells were encapsulated by polyelectrolyte and enzyme layers. The biological activity of the Arxula was retained after the encapsulation process. The polymeric capsule surrounding the Arxula provides a stable interface for surface engineering of living cells. LbL of polyelectrolytes followed by an enzyme layer of lactate oxidase were assembled. The outer enzyme layer provides an additional biological function for Arxula to convert the unfavourable substrate lactate into the favourable substrate pyruvate, thus extending the substrate spectrum of the organism. Moreover, capsule stability and enzyme conjugate stability of the surface engineered Arxula were studied.

  • 31.
    Mansor, Nur Azimah
    et al.
    Universiti Teknologi MARA, Shah Alam, Malaysia.
    Zain, Zainiharyati Mohd
    Universiti Teknologi MARA, Shah Alam, Malaysia.
    Hamzah, Hairul Hisham
    Universiti Teknologi MARA, Shah Alam, Malaysia.
    Noorden, Mohd Shihabuddin Ahmad
    Universiti Teknologi MARA, Puncak Alam, Malaysia.
    Jaapar, Siti Safura
    Universiti Teknologi MARA, Puncak Alam, Malaysia.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Ibupoto, Zafar Husain
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Detection of Breast Cancer 1 (BRCA1) Gene Using an Electrochemical DNA Biosensor Based on Immobilized ZnO Nanowires2014In: Open Journal of Applied Biosensor, ISSN 2168-5401, Vol. 3, no 2, p. 9-17Article in journal (Refereed)
    Abstract [en]

    Herein we report an electrochemical DNA biosensor for the rapid detection of sequence (5’ AAT GGA TTT ATC TGC TCT TCG 3’) specific for the breast cancer 1 (BRCA1) gene. The proposed electrochemical genosensor is based on short oligonucleotide DNA probe immobilized onto zinc oxide nanowires (ZnONWs) chemically synthesized onto gold electrode via hydrothermal technique. The morphology studies of the ZnONWs, performed by field emission scanning electron microscopy (FESEM), showed that the ZnO nanowires are uniform, highly dense and oriented perpendicularly to the substrate. Recognition event between the DNA probe and the target was investigated by differential pulse voltammetry (DPV) in 0.1 M acetate buffer solution (ABS), pH 7.00; as a result of the hybridization, an oxidation signal was observed at +0.8 V. The influences of pH, target concentration, and non-complimentary DNA on biosensor performance were examined. The proposed DNA biosensor has the ability to detect the target sequence in the range of concentration between 10.0 and 100.0 µM with a detection limit of 3.32 µM. The experimental results demonstrated that the prepared ZnONWs/Au electrodes are suitable platform for the immobilization of DNA.

  • 32.
    Martinsson, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Nanoplasmonic Sensing using Metal Nanoparticles2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In our modern society, we are surrounded by numerous sensors, constantly feeding us information about our physical environment. From small, wearable sensors that monitor our physiological status to large satellites orbiting around the earth, detecting global changes. Although, the performance of these sensors have been significantly improved during the last decades there is still a demand for faster and more reliable sensing systems with improved sensitivity and selectivity. The rapid progress in nanofabrication techniques has made a profound impact for the development of small, novel sensors that enables miniaturization and integration. A specific area where nanostructures are especially attractive is biochemical sensing, where the exceptional properties of nanomaterials can be utilized in order to detect and analyze biomolecular interactions. 

    The focus of this thesis is to investigate plasmonic nanoparticles composed of gold or silver and optimize their performance as signal transducers in optical biosensors. Metal nanoparticles exhibit unique optical properties due to excitation of localized surface plasmons, which makes them highly sensitive probes for detecting small, local changes in their surrounding environment, for instance the binding of a biomolecule to the nanoparticle surface. This is the basic principle behind nanoplasmonic sensing based on refractometric detection, a sensing scheme that offers real-time and label-free detection of molecular interactions. 

    This thesis shows that the sensitivity for detecting local refractive index changes is highly dependent on the geometry of the metal nanoparticles, their interaction with neighboring particles and their chemical composition and functionalization. An increased knowledge about how these parameters affects the sensitivity is essential when developing nanoplasmonic sensing devices with high performance based on metal nanoparticles. 

    List of papers
    1. Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms
    Open this publication in new window or tab >>Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms