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Junaid, M., Hsiao, C.-L., Chen, Y.-T., Lu, J., Palisaitis, J., Persson, P. O., . . . Birch, J. (2018). Effects of N2 Partial Pressure on Growth, Structure, and Optical Properties of GaN Nanorods Deposited by Liquid-Target Reactive Magnetron Sputter Epitaxy. Nanomaterials, 8(4), Article ID 223.
Open this publication in new window or tab >>Effects of N2 Partial Pressure on Growth, Structure, and Optical Properties of GaN Nanorods Deposited by Liquid-Target Reactive Magnetron Sputter Epitaxy
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2018 (English)In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 4, article id 223Article in journal (Other academic) Published
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.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI, 2018
Keywords
GaN, nanorods, X-ray diffraction, TEM, photoluminescence, magnetron sputter epitaxy, sputtering
National Category
Condensed Matter Physics Nano Technology
Identifiers
urn:nbn:se:liu:diva-84654 (URN)10.3390/nano8040223 (DOI)
Available from: 2018-04-09 Created: 2012-10-16 Last updated: 2018-04-24Bibliographically approved
Leiqiang, Q., Tao, Q., El Ghazaly, A., Fernandez-Rodriguez, J., Persson, P., Rosén, J. & Zhang, F. (2018). High-Performance Ultrathin Flexible Solid-State Supercapacitors Based on Solution Processable Mo1.33C MXene and PEDOT:PSS. Advanced Functional Materials, 28(2), Article ID 1703808.
Open this publication in new window or tab >>High-Performance Ultrathin Flexible Solid-State Supercapacitors Based on Solution Processable Mo1.33C MXene and PEDOT:PSS
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2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 2, article id 1703808Article in journal (Refereed) Published
Abstract [en]

MXenes, a young family of 2D transition metal carbides/nitrides, show great potential in electrochemical energy storage applications. Herein, a high performance ultrathin flexible solid-state supercapacitor is demonstrated based on a Mo1.33C MXene with vacancy ordering in an aligned layer structure MXene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) composite film posttreated with concentrated H2SO4. The flexible solid-state supercapacitor delivers a maximum capacitance of 568 F cm-3, an ultrahigh energy density of 33.2 mWh cm-3 and a power density of 19 470 mW cm-3. The Mo1.33C MXene/PEDOT:PSS composite film shows a reduction in resistance upon H2SO4 treatment, a higher capacitance (1310 F cm-3) and improved rate capabilities than both pristine Mo1.33C MXene and the nontreated Mo1.33C/PEDOT:PSS composite films. The enhanced capacitance and stability are attributed to the synergistic effect of increased interlayer spacing between Mo1.33C MXene layers due to insertion of conductive PEDOT, and surface redox processes of the PEDOT and the MXene.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
composite films; Mo1.33C; MXene; PEDOT:PSS; solid-state supercapacitors
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-144437 (URN)10.1002/adfm.201703808 (DOI)000419454000003 ()
Note

Funding Agencies|Swedish Energy Agency [EM 42033-1]; SSF Synergy Grant FUNCASE; SSF Research Infrastructure Fellow program [RIF 14-0074, RIF14-0079]; Knut and Alice Wallenberg (KAW) Foundation [KAW 2015.0043]; Swedish Research Council (VR) [642-2013-8020]

Available from: 2018-01-23 Created: 2018-01-23 Last updated: 2018-02-20
Persson, I., Näslund, L.-Å., Halim, J., Barsoum, M., Darakchieva, V., Palisaitis, J., . . . Persson, P. O. (2018). On the organization and thermal behavior of functional groups on Ti3C2 MXene surfaces in vacuum. 2D MATERIALS, 5(1), Article ID 015002.
Open this publication in new window or tab >>On the organization and thermal behavior of functional groups on Ti3C2 MXene surfaces in vacuum
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2018 (English)In: 2D MATERIALS, ISSN 2053-1583, Vol. 5, no 1, article id 015002Article in journal (Refereed) Published
Abstract [en]

The two-dimensional (2D) MXene Ti(3)C(2)Tx is functionalized by surface groups (T-x) that determine its surface properties for, e.g. electrochemical applications. The coordination and thermal properties of these surface groups has, to date, not been investigated at the atomic level, despite strong variations in the MXene properties that are predicted from different coordinations and from the identity of the functional groups. To alleviate this deficiency, and to characterize the functionalized surfaces of single MXene sheets, the present investigation combines atomically resolved in situ heating in a scanning transmission electron microscope (STEM) and STEM simulations with temperature-programmed x-ray photoelectron spectroscopy (TP-XPS) in the room temperature to 750 degrees C range. Using these techniques, we follow the surface group coordination at the atomic level. It is concluded that the F and O atoms compete for the DFT-predicted thermodynamically preferred site and that at room temperature that site is mostly occupied by F. At higher temperatures, F desorbs and is replaced by O. Depending on the O/F ratio, the surface bare MXene is exposed as F desorbs, which enables a route for tailored surface functionalization.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
Keywords
MXene; Ti3C2Tx in situ heating; STEM; temperature-programmed XPS; surface functionalization
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-142131 (URN)10.1088/2053-1583/aa89cd (DOI)000412302100002 ()
Note

Funding Agencies|Swedish Research Council [621-20124359, 622-2008-405, 2013-5580, 2016-04412, 642-2013-8020]; Knut and Alice Wallenbergs Foundation [KAW 2015.0043]; Swedish Foundation for Strategic Research (SSF) [RIF14-0074]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2017-11-16Bibliographically approved
Palisaitis, J., Persson, I., Halim, J., Rosén, J. & Persson, P. O. Å. (2018). On the Structural Stability of MXene and the Role of Transition Metal Adatoms. Nanoscale
Open this publication in new window or tab >>On the Structural Stability of MXene and the Role of Transition Metal Adatoms
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372Article in journal (Refereed) Accepted
Abstract [en]

In the present communication, the atomic structure and coordination of surface adsorbed species on Nb2C MXene is investigated over time. In particular, the influence of the Nb adatoms on the structural stability and oxidation behavior of the MXene is addressed. This investigation is based on plan-view geometry observations of single Nb2C MXene sheets by a combination of atomic-resolution scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and STEM image simulations.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
Keywords
2D material; MXene; Scanning Transmission Electron Microscopy; Structural Stability; Adatoms
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-148143 (URN)10.1039/C8NR01986J (DOI)29870038 (PubMedID)
Note

Funding agencies:The authors acknowledge the Swedish Research Council for funding under grants no. 2016- 04412 and 642-2013-8020, the Knut and Alice Wallenberg’s Foundation for support of the electron microscopy laboratory in Linköping, a Fellowship grant and a project grant (KAW 2015.0043). The authors also acknowledge Swedish Foundation for Strategic Research (SSF) through the Research Infrastructure Fellow program no. RIF 14-0074. The authors finally acknowledge support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No 2009 00971

Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2018-06-07Bibliographically approved
Serban, E. A., Palisaitis, J., Persson, P. O., Hultman, L., Birch, J. & Hsiao, C.-L. (2018). Site-controlled growth of GaN nanorod arrays by magnetron sputter epitaxy. Thin Solid Films
Open this publication in new window or tab >>Site-controlled growth of GaN nanorod arrays by magnetron sputter epitaxy
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2018 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731Article in journal (Refereed) Epub ahead of print
Abstract [en]

Catalyst-free GaN nanorod regular arrays have been realized by reactive magnetron sputter epitaxy. Two nanolithographic methods, nanosphere lithography (NSL) and focused ion beam lithography (FIBL), were applied to pattern Si substrates with TiNx masks. The growth temperature was optimized for achieving selectivity and well-faceted nanorods grown onto the NSL-patterned substrates. With increasing temperature from 875 to 985 °C, we observe different growth behaviors and associate them with selective insensitive, diffusion-dominated, and desorption-dominated zones. To further achieve site-specific and diameter control, these growth parameters were transferred onto FIBL-patterned substrates. Further investigation into the FIBL process through tailoring of milling current and time in combination with varying nanorod growth temperature, suggests that minimization of mask and substrate damage is the key to attain uniform, well-defined, single, and straight nanorods. Destruction of the mask results in selective area growth failure, while damage of the substrate surface promotes inclined nanorods grown into the openings, owning to random oriented nucleation.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Gallium nitride, Magnetron sputter epitaxy, Selective-area growth, Nanorods, Lithography, Focused ion beam, Nanosphere
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-147648 (URN)10.1016/j.tsf.2018.01.050 (DOI)2-s2.0-85041572645 (Scopus ID)
Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-06-18Bibliographically approved
Serban, A., Palisaitis, J., Junaid, M., Tengdelius, L., Högberg, H., Hultman, L., . . . Hsiao, C.-L. (2017). Magnetron Sputter Epitaxy of High-Quality GaN Nanorods on Functional and Cost-Effective Templates/Substrates. Energies, 10(9), Article ID 1322.
Open this publication in new window or tab >>Magnetron Sputter Epitaxy of High-Quality GaN Nanorods on Functional and Cost-Effective Templates/Substrates
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2017 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, no 9, article id 1322Article in journal (Refereed) Published
Abstract [en]

We demonstrate the versatility of magnetron sputter epitaxy by achieving high-quality GaN nanorods on different substrate/template combinations, specifically Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti. Growth temperature was optimized on Si, TiN/Si, and ZrB2/Si, resulting in increased nanorod aspect ratio with temperature. All nanorods exhibit high purity and quality, proved by the strong bandedge emission recorded with cathodoluminescence spectroscopy at room temperature as well as transmission electron microscopy. These substrates/templates are affordable compared to many conventional substrates, and the direct deposition onto them eliminates cumbersome post-processing steps in device fabrication. Thus, magnetron sputter epitaxy offers an attractive alternative for simple and affordable fabrication in optoelectronic device technology.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI AG, 2017
Keywords
GaN, nanorods, Si, SiC, Ti, Mo, TiN and ZrB2 templates, magnetron sputtering, epitaxy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-141597 (URN)10.3390/en10091322 (DOI)000411225200078 ()2-s2.0-85029362447 (Scopus ID)
Note

Funding agencies: Swedish Research Council (VR) [621-2012-4420, 621-2013-5360, 2016-04412]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program; Swedish Foundation for Strategic Research (SSF) through the Resea

Available from: 2017-10-02 Created: 2017-10-02 Last updated: 2018-05-03Bibliographically approved
Zhu, B., Seifeddine, S., Persson, P. O., Jarfors, A. E. W., Leisner, P. & Zanella, C. (2016). A study of formation and growth of the anodised surface layer on cast Al-Si alloys based on different analytical techniques. Materials & design, 101, 254-262
Open this publication in new window or tab >>A study of formation and growth of the anodised surface layer on cast Al-Si alloys based on different analytical techniques
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2016 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 101, p. 254-262Article in journal (Refereed) Published
Abstract [en]

This paper aims to investigate the mechanisms of formation and growth of the anodised surface layer on Al-Si castings by applying different analytical techniques such as optical microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and X-ray computer tomography (X-ray CT) scanning. Three different Al alloys with various Si content (2.43%, 3.53% and 5.45%) were investigated. Si particle morphological modification by Sr addition, as well as directional solidification, was used to vary the microstructural coarseness in a controlled manner to study the influence of these parameters on the growth behaviour of the oxide layer. This study observed residual unanodised Al phases trapped beneath or between Si particles in the oxide layer. It was found, depending on the geometry and morphology of Si particles, that Al can be shielded by Si particles and prevented from oxidising. (C) 2016 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Al-Si cast alloys; Anodising; Oxide layers; Silicon
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-128713 (URN)10.1016/j.matdes.2016.04.013 (DOI)000375413100032 ()
Note

Funding Agencies|Knowledge Foundation (RHEOCAL, as part of CompCast) [201000280]

Available from: 2016-06-07 Created: 2016-05-30 Last updated: 2017-11-30
Tholander, C., Birch, J., Tasnádi, F., Hultman, L., Palisaitis, J., Persson, P. O., . . . Zukauskaitè, A. (2016). Ab initio calculations and experimental study of piezoelectric YxIn1-xN thin films deposited using reactive magnetron sputter epitaxy. Acta Materialia, 105, 199-206
Open this publication in new window or tab >>Ab initio calculations and experimental study of piezoelectric YxIn1-xN thin films deposited using reactive magnetron sputter epitaxy
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 105, p. 199-206Article in journal (Refereed) Published
Abstract [en]

By combining theoretical prediction and experimental verification we investigate the piezoelectric properties of yttrium indium nitride (YxIn1-xN). Ab initio calculations show that the YxIn1-xN wurtzite phase is lowest in energy among relevant alloy structures for 0≤x≤0.5. Reactive magnetron sputter epitaxy was used to prepare thin films with Y content up to x=0.51. The composition dependence of the lattice parameters observed in the grown films is in agreement with that predicted by the theoretical calculations confirming the possibility to synthesize a wurtzite solid solution. An AlN buffer layer greatly improves the crystalline quality and surface morphology of subsequently grown YxIn1-xN films. The piezoelectric response in films with x=0.09 and x=0.14 is observed using piezoresponse force microscopy. Theoretical calculations of the piezoelectric properties predict YxIn1−xN to have comparable piezoelectric properties to ScxAl1-xN.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
YInN, Thin films, Sputter deposition, Piezoelectricity, Ab initio calculations
National Category
Condensed Matter Physics Materials Chemistry Inorganic Chemistry Other Materials Engineering Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:liu:diva-125918 (URN)10.1016/j.actamat.2015.11.050 (DOI)000370086500023 ()
Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2017-11-30Bibliographically approved
Hunold, O., Chen, Y.-T., Music, D., Persson, P. O., Primetzhofer, D., Moritz Baben; Achenbach, J.-O., . . . Schneider, J. M. (2016). Correlative theoretical and experimental investigation of the formation of AIYB(14) and competing phases. Journal of Applied Physics, 119(8), 085307
Open this publication in new window or tab >>Correlative theoretical and experimental investigation of the formation of AIYB(14) and competing phases
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 8, p. 085307-Article in journal (Refereed) Published
Abstract [en]

The phase formation in the boron-rich section of the Al-Y-B system has been explored by a correlative theoretical and experimental research approach. The structure of coatings deposited via high power pulsed magnetron sputtering from a compound target was studied using elastic recoil detection analysis, electron energy loss spectroscopy spectrum imaging, as well as X-ray and electron diffraction data. The formation of AlYB14 together with the (Y,Al)B-6 impurity phase, containing 1.8 at. % less B than AlYB14, was observed at a growth temperature of 800 degrees C and hence 600 degrees C below the bulk synthesis temperature. Based on quantum mechanical calculations, we infer that minute compositional variations within the film may be responsible for the formation of both icosahedrally bonded AlYB14 and cubic (Y,Al)B-6 phases. These findings are relevant for synthesis attempts of all boron rich icosahedrally bonded compounds with the space group: Imma that form ternary phases at similar compositions. (C) 2016 AIP Publishing LLC.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-126840 (URN)10.1063/1.4942664 (DOI)000371601800053 ()
Note

Funding Agencies|Deutsche Forschungsgemeinschaft within the Collaborative Research Center [SFB-TR 87/2]; JARA-HPC from RWTH Aachen University [JARA0131]; Knut and Alice Wallenberg Foundation

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-11-30
Moubah, R., Magnus, F., Warnatz, T., Palsson, G. K., Kapaklis, V., Devishvili, A., . . . Hjörvarsson, B. (2016). Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices. Physical Review Applied, 5(044011)
Open this publication in new window or tab >>Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices
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2016 (English)In: Physical Review Applied, ISSN 2331-7019, Vol. 5, no 044011Article in journal (Refereed) Published
Abstract [en]

We report on a discrete layer-by-layer magnetic switching in Fe=MgO superlattices driven by anantiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunnelingthrough MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgOthickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropystabilizes both 90° and 180° periodic alignment of adjacent layers throughout the entire superlattice. Thetunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe=MgO=Fejunctions, is an appealing combination for three-dimensional spintronic memories and logic devices.

Place, publisher, year, edition, pages
American physical society, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128109 (URN)10.1103/PhysRevApplied.5.044011 (DOI)000374562100001 ()
Note

Funding agencies: Swedish research council (VR); Knut and Alice Wallenberg Foundation (KAW)

Available from: 2016-05-17 Created: 2016-05-17 Last updated: 2016-06-10
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9140-6724

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