| 1. |
- Anastasopoulos, M., et al.
(author)
-
Multi-Grid detector for neutron spectroscopy : Results obtained on time-of-flight spectrometer CNCS
- 2017
-
In: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 12:4
-
Journal article (peer-reviewed)abstract
- The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of 3He detectors on an operational instrument. The demonstrator has an active area of 0.2 m2. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the 3He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by 3He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS.
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| 2. |
- Andersen, Ken, et al.
(author)
-
B-10 multi-grid proportional gas counters for large area thermal neutron detectors
- 2013
-
In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002 .- 1872-9576. ; 720, s. 116-121
-
Journal article (peer-reviewed)abstract
- He-3 was a popular material in neutrons detectors until its availability dropped drastically in 2008. The development of techniques based on alternative convertors is now of high priority for neutron research institutes. Thin films of B-10 or (B4C)-B-10 have been used in gas proportional counters to detect neutrons, but until now, only for small or medium sensitive area. We present here the multi-grid design, introduced at the ILL and developed in collaboration with ESS for LAN (large area neutron) detectors. Typically thirty (B4C)-B-10 films of 1 mu m thickness are used to convert neutrons into ionizing particles which are subsequently detected in a proportional gas counter. The principle and the fabrication of the multi-grid are described and some preliminary results obtained with a prototype of 200 cm x 8 cm are reported; a detection efficiency of 48% has been measured at 2.5 angstrom with a monochromatic neutron beam line, showing the good potential of this new technique. (C) 2013 Elsevier B.V. All rights reserved.
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| 3. |
- Ben Sedrine, Nabiha, et al.
(author)
-
Infrared dielectric functions and optical phonons of wurtzite YxAl1-xN (0 less than= x less than= 0.22)
- 2015
-
In: Journal of Physics D. - : IOP PUBLISHING LTD. - 0022-3727 .- 1361-6463. ; 48:41, s. 415102-
-
Journal article (peer-reviewed)abstract
- YAlN is a new member of the group-III nitride family with potential for applications in next generation piezoelectric and light emitting devices. We report the infrared dielectric functions and optical phonons of wurtzite (0001) YxAl1-xN epitaxial films with 0 less than= x less than= 0.22. The films are grown by magnetron sputtering epitaxy on c-plane Al2O3 and their phonon properties are investigated using infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The infrared-active E-1(TO) and LO, and the Raman active E-2 phonons are found to exhibit one-mode behavior, which is discussed in the framework of the MREI model. The compositional dependencies of the E-1(TO), E-2 and LO phonon frequencies, the high-frequency limit of the dielectric constant, epsilon(infinity), the static dielectric constant, epsilon(0), and the Born effective charge Z(B) are established and discussed.
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| 4. |
- Eklund, Per, et al.
(author)
-
Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
- 2005
-
In: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:6, s. 2486-2495
-
Journal article (peer-reviewed)abstract
- We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300 °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290 GPa, respectively. The electrical resistivity was 330 µ cm for optimal Ar pressure (4 mTorr) and substrate temperature (300 °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6 µ at a contact force of 800 N compared to 3.2 µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.
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| 5. |
- Hsiao, Ching-Lien, et al.
(author)
-
Room-temperature heteroepitaxy of single-phase Al1-xInxN films with full composition range on isostructural wurtzite templates
- 2012
-
In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 524, s. 113-120
-
Journal article (peer-reviewed)abstract
- Al1-xInxN heteroepitaxial layers covering the full composition range have been realized by magnetron sputter epitaxy on basal-plane AlN, GaN, and ZnO templates at room temperature (RT). Both Al1-xInxN single layers and multilayers grown on these isostructural templates show single phase, single crystal wurtzite structure. Even at large lattice mismatch between the film and the template, for instance InN/AlN (similar to 13% mismatch), heteroepitaxy is achieved. However, RT-grown Al1-xInxN films directly deposited on non-isostructural c-plane sapphire substrate exhibit a polycrystalline structure for all compositions, suggesting that substrate surface structure is important for guiding the initial nucleation. Degradation of Al1-xInxN structural quality with increasing indium content is attributed to the formation of more point-and structural defects. The defects result in a prominent hydrostatic tensile stress component, in addition to the biaxial stress component introduced by lattice mismatch, in all RT-grown Al1-xInxN films. These effects are reflected in the measured in-plane and out-of-plane strains. The effect of hydrostatic stress is negligible compared to the effects of lattice mismatch in high-temperature grown AlN layers thanks to their low amount of defects. We found that Vegards rule is applicable to determine x in the RT-grown Al1-xInxN epilayers if the lattice constants of RT-sputtered AlN and InN films are used instead of those of the strain-free bulk materials.
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| 6. |
- Högberg, Hans, 1968-, et al.
(author)
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Epitaxial Ti2GeC, Ti3GeC2, and Ti4GeC3 MAX-phase thin films grown by magnetron sputtering
- 2005
-
In: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 20:4, s. 779-782
-
Journal article (peer-reviewed)abstract
- We have grown single-crystal thin films of Ti2GeC and Ti3GeC2 and a new phase Ti4GeC3, as well as two new intergrown MAX-structures, Ti5Ge2C3 and Ti7Ge2C5. Epitaxial films were grown on Al2O3(0001) substrates at 1000 °C using direct current magnetron sputtering. X-ray diffraction shows that Ti–Ge–C MAX-phases require higher deposition temperatures in a narrower window than their Ti–Si–C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young’s modulus of 300 GPa, lower than that of Ti3SiC2. Four-point probe measurements yield resistivity values of 50–200 μΩcm. The lowest value is obtained for phase-pure Ti3GeC2(0001) films.
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| 7. |
- Höglund, Carina, et al.
(author)
-
B4C thin films for neutron detection
- 2012
-
In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 111:10
-
Journal article (peer-reviewed)abstract
- Due to the very limited availability of He-3, new kinds of neutron detectors, not based on 3He, are urgently needed. Here, we present a method to produce thin films of (B4C)-B-10, with maximized detection efficiency, intended to be part of a new generation of large area neutron detectors. B4C thin Films have been deposited onto Al-blade and Si wafer substrates by dc magnetron sputtering from (B4C)-B-nat and (B4C)-B-10 targets in an Ar discharge, using an industrial deposition system. The films were characterized with scanning electron microscopy, elastic recoil detection analysis, x-ray reflectivity, and neutron radiography. We show that the film-substrate adhesion and film purity are improved by increased substrate temperature and deposition rate. A deposition rate of 3.8 angstrom/s and substrate temperature of 400 degrees C result in films with a density close to bulk values and good adhesion to film thickness above 3 mu m. Boron-10 contents of almost 80 at. % are obtained in 6.3 m(2) of 1 mu m thick (B4C)-B-10 thin films coated on Al-blades. Initial neutron absorption measurements agree with Monte Carlo simulations and show that the layer thickness, number of layers, neutron wavelength, and amount of impurities are determining factors. The study also shows the importance of having uniform layer thicknesses over large areas, which for a full-scale detector could be in total similar to 1000 m(2) of two-side coated Al-blades with similar to 1 mu m thick (B4C)-B-10 films.
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| 8. |
- Höglund, Carina, et al.
(author)
-
Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions
- 2010
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:22, s. 224101-
-
Journal article (peer-reviewed)abstract
- Thin solid films of metastable rocksalt structure (c-) Sc1-xAlxN and Ti1-xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N(111) and Ti0.51Al0.49N(111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using X-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000 °C – 1100 °C into non-isostructural c-ScN and wurtzite-structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800 °C – 1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001) || ScN(001) and AlN<01ɸ10> || ScN<1ɸ10>. First principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.
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| 9. |
- Höglund, Carina, et al.
(author)
-
Growth and oxidization stability of cubic Zr1-xGdxN solid solution thin films
- 2015
-
In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 117:19
-
Journal article (peer-reviewed)abstract
- We report Zr1-xGdxN thin films deposited by magnetron sputter deposition. We show a solid solubility of the highly neutron absorbing GdN into ZrN along the whole compositional range, which is in excellent agreement with our recent predictions by first-principles calculations. An oxidization study in air shows that Zr1-xGdxN with x reaching from 1 to close to 0 fully oxidizes, but that the oxidization is slowed down by an increased amount of ZrN or stopped by applying a capping layer of ZrN. The crystalline quality of Zr0.5Gd0.5N films increases with substrate temperatures increasing from 100 degrees C to 900 degrees C.
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| 10. |
- Höglund, Carina, et al.
(author)
-
Stability of (B4C)-B-10 thin films under neutron radiation
- 2015
-
In: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 113, s. 14-19
-
Journal article (peer-reviewed)abstract
- Thin films of (B4C)-B-10 have shown to be very suitable as neutron-converting material in the next generation of neutron detectors, replacing the previous predominantly used He-3. In this contribution we show under realistic conditions that (B4C)-B-10 films are not damaged by the neutron irradiation and interactions, which they will be exposed to under many years in a neutron detector. 1 mu m thick (B4C)-B-10 thin films were deposited onto Al or Si substrates using dc magnetron sputtering. As-deposited films were exposed to a cold neutron beam with fluences of up to 1.1 x 10(14) cm(-2) and a mean wavelength of 6.9 angstrom. Both irradiated and as-deposited reference samples were characterized with time-of-flight elastic recoil detection analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy, and X-ray diffraction. We show that only 1.8 ppm of the B-10 atoms were consumed and that the film composition does not change by the neutron interaction within the measurement accuracy. The irradiation does not deteriorate the film adhesion and there is no indication that it results in increased residual stress values of the as-deposited films of 0.095 GPa. From what is visible with the naked eye and down to atomic level studies, no change from the irradiation could be found using the above-mentioned characterization techniques. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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| 11. |
- Imam, Mewlude, et al.
(author)
-
Gas phase chemical vapor deposition chemistry of triethylboron probed by boron-carbon thin film deposition and quantum chemical calculations
- 2015
-
In: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 3:41, s. 10898-10906
-
Journal article (peer-reviewed)abstract
- We present triethylboron (TEB) as a single-source precursor for chemical vapor deposition (CVD) of BxC thin films and study its gas phase chemistry under CVD conditions by quantum chemical calculations. A comprehensive thermochemical catalogue for the species of the gas phase chemistry of TEB is examined and found to be dominated by beta-hydride eliminations of C2H4 to yield BH3. A complementary bimolecular reaction path based on H-2 assisted C2H6 elimination to BH3 is also significant at lower temperatures in the presence of hydrogen. Furthermore, we find a temperature window of 600-1000 degrees C for the deposition of X-ray amorphous BxC films with 2.5 less than= x less than= 4.5 from TEB. Films grown at temperatures below 600 degrees C contain high amounts of H, while temperatures above 1000 degrees C result in C-rich films. The film density and hardness are determined to be in the range of 2.40-2.65 g cm(-3) and 29-39 GPa, respectively, within the determined temperature window.
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| 12. |
- Imam, Mewlude, et al.
(author)
-
Trimethylboron as Single-Source Precursor for Boron-Carbon Thin Film Synthesis by Plasma Chemical Vapor Deposition
- 2016
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:38, s. 21990-21997
-
Journal article (peer-reviewed)abstract
- Boron carbon (BxC) thin films are potential neutron converting layers for B-10-based neutron detectors. However, as common material choices for such detectors do not tolerate temperatures above 500 degrees C, a low temperature deposition route is required. Here, we study trimethylboron B(CH3)(3) (TMB) as a single-source precursor for the deposition of BxC thin films by plasma CVD using Ar plasma. The effect of plasma power, TMB/Ar flow ratio and total pressure, on the film composition, morphology, chemical bonding, and microstructures are investigated. Dense and boron-rich films (B/C = 1.9) are achieved at high TMB flow under a low total pressure and high plasma power, which rendered an approximate substrate temperature of similar to 300 degrees C. Films mainly contain B-C bonds with the presence of B-O and C-C, which is attributed to be the origin of formed amorphous carbon in the films. The high H content 15 +/- 5 at. %) is almost independent of deposition parameters and contributed to lower the film density (2.16 g/cm(3)). The plasma compositional analysis shows that the TMB molecule decomposes to mainly atomic H, C-2, BH, and CH. A plasma chemical model for the decomposition of TMB with BH and CH as the plausible film depositing species in the plasma is proposed.
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| 13. |
- Imam, Mewlude, et al.
(author)
-
Trimethylboron as single-source precursor for boron-carbonthin film synthesis by plasma chemical vapor deposition
- 2015
-
Other publication (other academic/artistic)abstract
- Boron-carbon (BxC) thin films are potential neutron converting layers for 10B-based neutron detectors. However, as common material choices for such detectors do not tolerate temperature above 500°C, a low temperature deposition route is required for this application. Here we study trimethylboron B(CH3)3 (TMB) as a single-source precursor for the deposition of BxC thin films by plasma CVD using Ar plasma. The effect of plasma power, TMB/Ar ratio and total pressure on the film composition, morphology and structure are investigated. The highest B/C ratio of 1.9 was achieved at high TMB flow in a low total pressure and high plasma power which rendered an approximate substrate temperature of ~ 300 °C. X-ray photoelectron spectroscopy shows that B-C bonds prevail in the films, although C-C and B-O bonds are also present. Raman spectroscopy confirms the presence of amorphous carbon phases in the films. The H content in the films is found to be 15±5 at. % by the time of flight elastic recoil detection analysis (Tof-ERDA). The film density as determined from X-ray reflectivity (XRR) measurements is 2. 16 ± 0.01 g/cm3 and the internal compressive stresses are measured to be less than 400 MPa.
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| 14. |
- Jafari, Mohammad Javad, et al.
(author)
-
Thermal degradation of TiN and TiAlN coatings during rapid laser treatment
- 2021
-
In: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 422
-
Journal article (peer-reviewed)abstract
- In this research, a fundamental study was conducted on damage behavior of cathodic arc evaporated TiN and Ti0.44Al0.56N coatings, in terms of oxidation and cracking/spallation, when they were exposed to single-pulse laser treatment in a temperature range of 1200-2100 degrees C. Moreover, a multiple-pulse laser treatment was designed to apply thermo-mechanical loads on the coatings in order to evaluate their thermal degradation during rapid heating/cooling cycles between 200 and 1200 degrees C. Single-pulse treatment of TiN up to 1500 degrees C led to the intercolumnar cracking and formation of ultrafine TiO grains. An increase in temperature up to 2100 degrees C resulted in a notable bulging of the surface, and formation of TiO2 of various morphologies such as grainy structure, dense molten and re-solidified structure, droplets from melt expulsion and, more interestingly, nanofibers. Multiplepulse treatment of TiN was accompanied by a severe cracking and spallation, which divided the surface into two layers: a heavily cracked top layer composed of dense TiO2 grains, and a bottom layer having porous TiO2 grains indicating incomplete oxidation. Conversely, Ti0.44Al0.56N did not show any visible cracking and oxidation after single-pulse treatment. Multiple-pulse treatment did not also yield cracking and spallation for Ti0.44Al0.56N, and its ablated region consisted of TiO2 grains combined with thin Al2O3 platelets. An excellent combination of properties including higher oxidation resistance and greater fracture toughness at high temperatures led to a higher thermal damage resistance for Ti0.44Al0.56N coating compared to TiN when undergoing single- and multiple-pulse laser treatments.
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| 15. |
- Junaid, Muhammad, et al.
(author)
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Electronic-grade GaN(0001)/Al2O3(0001) grown by reactive DC-magnetron sputter epitaxy using a liquid Ga target
- 2011
-
In: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 98:14, s. 141915-
-
Journal article (peer-reviewed)abstract
- Electronic-grade GaN (0001) epilayers have been grown directly on Al2O3 (0001) substrates by reactive DC-magnetron sputter epitaxy (MSE) from a liquid Ga sputtering target in an Ar/N2 atmosphere. The as-grown GaN epitaxial film exhibit low threading dislocation density on the order of ≤ 1010 cm-2 obtained by transmission electron microscopy and modified Williamson-Hall plot. X-ray rocking curve shows narrow fullwidth at half maximum (FWHM) of 1054 arcsec of the 0002 reflection. A sharp 4 K photoluminescence peak at 3.474 eV with a FWHM of 6.3 meV is attributed to intrinsic GaN band edge emission. The high structural and optical qualities indicate that MSEgrown GaN epilayers can be used for fabricating high-performance devices without the need of any buffer layer.
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| 16. |
- Junaid, Muhammad, et al.
(author)
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Epitaxial Growth of GaN (0001)/Al2O3 (0001) by Reactive High Power Impulse Magnetron Sputter Deposition
-
Other publication (other academic/artistic)abstract
- Epitaxial GaN (0001) thin films were grown on Al2O3 (0001) substrates by reactive high power impulse magnetron sputtering of liquid Ga targets in a mixed N2/Ar discharge. A combination of x-ray diffraction, electron microscopy, atomic force microscopy, μ-Raman mapping and spectroscopy, μ-photoluminescence, time of flight elastic recoil detection, and cathodoluminescence showed the formation of relaxed and strained domains in the same films. While the strained domains form due to ion bombardment during growth, the relaxed domains exhibit
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| 17. |
- Kerdsongpanya, Sit, et al.
(author)
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Anomalously high thermoelectric power factor in epitaxial ScN thin films
- 2011
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 99:23, s. 232113-
-
Journal article (peer-reviewed)abstract
- Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al2O3(0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (similar to 1 at. % in total) of C, O, and F. We found that the ScN thin-film exhibits a rather low electrical resistivity of similar to 2.94 mu Omega m, while its Seebeck coefficient is approximately similar to-86 mu V/K at 800 K, yielding a power factor of similar to 2.5 x 10(-3) W/mK(2). This value is anomalously high for common transition-metal nitrides.
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| 18. |
- Khatibi, Ali, et al.
(author)
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Face-Centered Cubic (Al1-xCrx)2O3
- 2011
-
In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 519:8, s. 2426-2429
-
Journal article (peer-reviewed)abstract
- We report the discovery of a face-centered cubic (Al1−xCrx)2O3 solid solution [0.60bxb0.70] in films grownonto Si substrates using reactive radio frequency magnetron sputtering from Al and Cr targets at 400 °C. Theproposed structure is NaCl-like with 33% vacancies on the metal sites. The unit cell parameter is 4.04 Å asdetermined by X-ray diffraction. The films have a b100N preferred crystallographic orientation and exhibithardness values up to 26 GPa and an elastic modulus of 220–235 GPa.
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| 19. |
- Kindlund, Hanna, et al.
(author)
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Microstructure and mechanical properties of : V0.5Mo0.5Nx(111)/Al2O3(0001) thin films
- 2014
-
Other publication (other academic/artistic)abstract
- We report results of growth, microstructure, and mechanical properties of V0.5Mo0.5Nx thin films deposited on Al2O3(0001) substrates by reactive magnetron sputtering. Sputtering is carried out in 5 mTorr Ar/N2 atmospheres and the growth temperatures Ts are varied between 100 and 900 °C. We find that the V0.5Mo0.5Nx/Al2O3(0001) alloy films are 111-oriented NaCl-structure. In-plane and out-of plane lattice parameters are found to decrease with increasing Ts and indicate that all alloy films are strained. V0.5Mo0.5Nx hardnesses and reduced elastic moduli increase with increasing Ts, and vary between 15-23 GPa, and 220-318 GPa, respectively. The wear resistance of the alloy films is also found to increase with increasing Ts. In addition, scanning electron micrographs of indents performed on V0.5Mo0.5Nx films show material pile-up around the indent edges and no evidence of crack arising from nanoindentation experiments. Coefficients of friction acquired at normal forces of 1000 μN are found to be of the order of 0.09.
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| 20. |
- Kindlund, Hanna, et al.
(author)
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Toughness Enhancement in Hard Ceramic Thin Films by Alloy Design
- 2013
-
In: APL Materials. - : American Institute of Physics (AIP). - 2166-532X. ; 1:4, s. 042104-
-
Journal article (peer-reviewed)abstract
- Hardness is an essential property for a wide range of applications. However, hardness alone, typically accompanied by brittleness, is not sufficient to prevent failure in ceramic films exposed to high stresses. Using VN as a model system, we demonstrate with experiment and density functional theory (DFT) that refractory VMoN alloys exhibit not only enhanced hardness, but dramatically increased ductility. V0.5Mo0.5N hardness is 25% higher than that of VN. In addition, while nanoindented VN, as well as TiN reference samples, suffer from severe cracking typical of brittle ceramics, V0.5Mo0.5N films do not crack. Instead, they exhibit material pile-up around nanoindents, characteristic of plastic flow in ductile materials. Moreover, the wear resistance of V0.5Mo0.5N is considerably higher than that of VN. DFT results show that tuning the occupancy of d-t2g metallic bonding states in VMoN facilitates dislocation glide, and hence enhances toughness, via the formation of stronger metal/metal bonds along the slip direction and weaker metal/N bonds across the slip plane.
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| 21. |
- Kindlund, Hanna, et al.
(author)
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V0.5Mo0.5Nx/MgO(001): Composition, nanostructure, and mechanical properties as a function of film growth temperature
- 2017
-
In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 126, s. 194-201
-
Journal article (peer-reviewed)abstract
- V(0.5)Mo(0.5)Nx/MgO(001) alloys with the B1-NaCI structure are grown by ultra-high-vacuum reactive magnetron sputter deposition in 5 mTorr mixed Ar/N-2 atmospheres at temperatures T-s between 100 and 900 degrees C. Alloy films grown at T-s amp;lt;= 500 degrees C are polycrystalline with a strong 002 preferred orientation; layers grown at T-s amp;gt;= 700 degrees C are epitaxial single-crystals. The N/Metal composition ratio x ranges from 1.02 +/- 0.05 with T-s = 100-500 degrees C to 0.94 +/- 0.05 at 700 degrees C to 0.64 +/- 0.05 at T-s = 900 degrees C. N loss at higher growth temperatures leads to a corresponding decrease in the relaxed lattice parameter a(0) from 4.212 A with x = 1.02 to 4.175 angstrom at x = 0.94 to 4.120 angstrom with x = 0.64. V(0.5)Mo(0.5)Nx nanoindentation hardnesses H and elastic moduli E increase with increasing T-s, from 17 +/- 3 and 323 +/- 30 GPa at 100 degrees C to 26 +/- 1 and 370 +/- 10 GPa at 900 degrees C. Both polycrystalline and single-crystal V(0.5)Mo(0.5)Nx films exhibit higher toughnesses than that of the parent binary compound VN. V(0.5)Mo(0.5)Nx films deposited at higher Ts also exhibit enhanced wear resistance. Valence-band x-ray photoelectron spectroscopy analyses reveal an increased volume density of shear-sensitive d-t(2g) d-t(2g) metallic states for V(0.5)Mo(0.5)Nx compared to VN and the density of these orbitals increases with increasing deposition temperature, i.e., with increasing N-vacancy concentration.(C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 22. |
- Kindlund, Hanna, et al.
(author)
-
V0.5Mo0.5Nx/MgO(001) layers grown at 100-900 °C : composition, nanostructure, and mechanical properties
- 2014
-
Other publication (other academic/artistic)abstract
- V0.5Mo0.5Nx/MgO(001) alloys with the B1-NaCl structure are grown by ultra-highvacuum reactive magnetron sputter deposition in 5 mTorr mixed Ar/N2 atmospheres at temperatures Ts which are varied from 100 and 900 °C. Alloy films grown at Ts ≤ 500 °C are polycrystalline with a strong 002 texture; layers grown at Ts ≤ 700 °C are epitaxial single-crystals. The N/Me ratio x ranges from 0.64±0.05 with Ts = 900 °C to 0.94±0.05 at 700 °C to 1.02±0.05 with Ts = 500 to 100 °C. The N loss at higher growth temperatures leads to a corresponding decrease in the relaxed lattice parameter ao from 4.212 Å with x = 1.02 to 4.175 Å with x = 0.94 to 4.121 Å with x = 0.64. V0.5Mo0.5Nx nanoindentation hardnesses H and elastic moduli E increase with increasing Ts from 17±3 GPa and 274±31 GPa at 100 °C to 26±1 GPa and 303±10 GPa at 900 °C. Films deposited at higher Ts also exhibit enhanced wear resistance. Scanning electron micrographs of nanoindents performed in single-crystal V0.5Mo0.5Nx films and films deposited at 100 and 300 °C reveal no evidence of cracking; instead they exhibit material pile-up around the indents characteristic of plastic flow in ductile materials. Valence band x-ray photoelectron spectroscopy analyses show an enhanced volume density of the shear sensitive d-t2g – d-t2g metallic states in V0.5Mo0.5Nx compared to VN and the density of these orbitals increases with increasing deposition temperature, i.e., the metallic states become more populated with the introduction of N vacancies.
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| 23. |
- Kindlund, Hanna, et al.
(author)
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Vacancy-induced toughening in hard single-crystal V0.5Mo0.5Nx/MgO(001) thin films
- 2014
-
In: Acta Materialia. - Oxford, England : Elsevier. - 1359-6454 .- 1873-2453. ; 77, s. 394-400
-
Journal article (peer-reviewed)abstract
- Using a combination of experiments and density functional theory (DFT), we demonstrate the first example of vacancy-induced toughening, in this case for epitaxial pseudobinary NaCl-structure substoichiometric V0.5Mo0.5Nx alloys, with N concentrations 0.55 ≤ x ≤ 1.03, grown by reactive magnetron sputter deposition. The nanoindentation hardness H(x) increases with increasing vacancy concentration from 17 GPa with x = 1.03 to 26 GPa with x = 0.55, while the elastic modulus E(x) remains essentially constant at 370 GPa. Scanning electron micrographs of indented regions show ductile plastic flow giving rise to material pile-up, rather than cracks as commonly observed for hard, but brittle, transition-metal nitrides. The increase in alloy hardness with an elastic modulus which remains constant with decreasing x, combined with the observed material pile-up around nanoindents, DFT-calculated decrease in shear to bulk moduli ratios, and increased Cauchy pressures (C12-C44), reveals a trend toward vacancy-induced toughening. Moreover, DFT crystal orbital overlap population analyses are consistent with the above results.
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| 24. |
- Muhammad, Junaid, et al.
(author)
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Two-domain formation during the epitaxial growth of GaN (0001) on c-plane Al2O3 (0001) by high power impulse magnetron sputtering
- 2011
-
In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 110:12, s. 123519-
-
Journal article (peer-reviewed)abstract
- We study the effect of high power pulses in reactive magnetron sputter epitaxy on the structural properties of GaN (0001) thin films grown directly on Al2O3 (0001) substrates. The epilayers are grown by sputtering from a liquid Ga target, using a high power impulse magnetron sputtering power supply in a mixed N2/Ar discharge. X-ray diffraction, micro-Raman, micro-photoluminescence, and transmission electron microscopy investigations show the formation of two distinct types of domains. One almost fully relaxed domain exhibits superior structural and optical properties as evidenced by rocking curves with a full width at half maximum of 885 arc sec and a low temperature band edge luminescence at 3.47 eV with the full width at half maximum of 10 meV. The other domain exhibits a 14 times higher isotropic strain component, which is due to the higher densities of the point and extended defects, resulting from the ion bombardment during growth. Voids form at the domain boundaries. Mechanisms for the formation of differently strained domains, along with voids during the epitaxial growth of GaN are discussed.
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| 25. |
- Nayak, Sanjay Kumar, et al.
(author)
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Dynamic evolution of internal stress, grain growth, and crystallographic texture in arc-evaporated AlTiN thin films using in-situ synchrotron x-ray diffraction
- 2024
-
In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 272
-
Journal article (peer-reviewed)abstract
- Understanding the nucleation and growth of polycrystalline thin films is a long-standing goal. Numerous studies have been done to determine the grain size, stress, and the ideal crystallographic orientation in films. The majority of past studies have either employed an ex-situ methodology or only monitor the development of macroscopic stress in real-time. There has never been any research done on the simultaneous changes in crystallographic texture, grain size, and microscopic stress in polycrystalline thin films. In this study, we investigated the generation and temporal evolution of texture, grain size, and internal stress in cathodic arc evaporated Al0.50Ti0.50N thin films using a bespoke deposition apparatus designed for use with 2-dimensional synchrotron x-ray diffraction technique. The influence of the substrate temperature is investigated in terms of the emergence and development of texture, grain size and stress evolution. A dynamic evolution of the crystallographic texture is observed as the overall film thickness varies. We clearly resolved two regime of films growth based on stress evolution. Beyond a threshold grain size (similar to 14 nm), the stress scales inversely to the average grain sizes, and as the film thickness increases, immediate compressive stress relaxation was seen. An extensive ex-situ evaluation of thin films using electron microscopies and electron diffraction was performed to support the in-situ x-ray diffraction results.
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| 26. |
- Olsson, Simon, et al.
(author)
-
Structure and Composition of Al(Si)CuFe Approximant Thin Films Formed by Si Substrate Diffusion
- 2014
-
In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 550:1, s. 105-109
-
Journal article (peer-reviewed)abstract
- Multilayered Al/Cu/Fe thin films with composition close to the quasicrystalline phase have been prepared by magnetron sputtering. Annealing at 600 °C yields a homogeneous film of the cubic a-approximant phase by Si substrate diffusion, which prevents the formation of the quasicrystalline phase. After 4 h annealing the film contained 8 at.% Si, which corresponds to the expected value of the a-approximant. The amount of Si in the films was found to slowly increase to ~12 at.% during continued annealing (64 h) while the α-approximant phase was retained. The lattice parameter was found to continuously decrease as Al became substituted with Si. The film is observed to be polycrystalline with individual grains being strained in varying magnitude, and with no preferential orientation relationship to the substrate or each other.
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| 27. |
- Olsson, Simon, et al.
(author)
-
Structure and Composition of Approximant Thin Films Formed by Substrate Diffusion
-
Other publication (other academic/artistic)abstract
- Multilayered Al/Cu/Fe thin films with composition close to the quasicrystalline phase have been prepared by magnetron sputtering. Annealing at 600 °C yields a homogeneous film of the cubic approximant phase by Si substrate diffusion, which prevented the formation of the quasicrystalline phase. After 4 h annealing the film contained 8 at.% Si corresponding well to the expected value of the approximant. The amount of Si in the films is found to slowly increase to ~12 at.% during continued annealing (64 h) while the approximant phase was retained. The lattice parameter was continuously decreasing as Si substituted for Al.
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| 28. |
- Palmquist, Jens-Petter, et al.
(author)
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Magnetron sputtered epitaxial single-phase Ti3SiC2 thin films
- 2002
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:5, s. 835-837
-
Journal article (peer-reviewed)abstract
- We report on the synthesis and characterization of epitaxial single-crystalline Ti3SiC2 films (Mn + 1AXn-phase). Two original deposition techniques are described, (i) magnetron sputtering from Ti3SiC2 compound target and (ii) sputtering from individual titanium and silicon targets with co-evaporated C60 as carbon source. Epitaxial Ti3SiC2 films of single-crystal quality were grown at 900 °C with both techniques. Epitaxial TiC(111) deposited in situ on MgO(111) by Ti sputtering using C60 as carbon source was used to nucleate the Ti3SiC2 films. The epitaxial relationship was found to be Ti3SiC2(0001)//TiC(111)//MgO(111) with the in-plane orientation Ti3SiC2[100]//TiC[101]//MgO[101].
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| 29. |
- Pedersen, Henrik, et al.
(author)
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Low Temperature CVD of Thin, Amorphous Boron-Carbon Films for Neutron Detectors
- 2012
-
In: Chemical Vapor Deposition. - : Wiley-VCH Verlag Berlin. - 0948-1907 .- 1521-3862. ; 18:7-9, s. 221-224
-
Journal article (peer-reviewed)abstract
- Thin, amorphous boron-carbon films are deposited at low temperature (400600?degrees C) by thermally activated CVD using the organoborane triethylboron (TEB) as a single precursor. Two different carrier gases are tested. At 600?degrees C, using argon as the carrier gas, the deposition rate is close to 1?mu m h-1. The film has a density of 2.14?g?cm-3 with a B/C ratio of 3.7. When hydrogen is used as the carrier gas, the film density is 2.42?g?cm-3, the B/C ratio 4.6, and the deposition rate 0.35?mu m h-1. The hydrogen content in the films is about 34 at.-%, regardless of ambient conditions during deposition, and varies only with the deposition temperature. In addition, both the film composition and the film density are found to vary significantly with the deposition temperature and the atmospheric conditions. Based upon these results, a deposition mechanism for the growth of boron-carbon films from TEB, where the TEB molecule is decomposed to BH3 and hydrocarbons, is suggested.
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| 30. |
- Schmidt, Susann, et al.
(author)
-
Low-temperature growth of boron carbide coatings by direct current magnetron sputtering and high-power impulse magnetron sputtering
- 2016
-
In: Journal of Materials Science. - New York : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 51:23, s. 10418-10428
-
Journal article (peer-reviewed)abstract
- B4C coatings for 10B-based neutron detector applications were deposited using high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) processes. The coatings were deposited on Si(001) as well as on flat and macrostructured (grooved) Al blades in an industrial coating unit using B4C compound targets in Ar. The HiPIMS and DCMS processes were conducted at substrate temperatures of 100 and 400 °C and the Ar pressure was varied between 300 and 800 mPa. Neutron detector-relevant coating characterization was performed and the coating properties were evaluated with regard to their growth rate, density, level of impurities, and residual coating stress. The coating properties are mainly influenced by general process parameters such as the Ar pressure and substrate temperature. The deposition mode shows only minor effects on the coating quality and no effects on the step coverage. At a substrate temperature of 100 °C and an Ar pressure of 800 mPa, well-adhering and functional coatings were deposited in both deposition modes; the coatings showed a density of 2.2 g/cm3, a B/C ratio of ~3.9, and the lowest compressive residual stresses of 180 MPa. The best coating quality was obtained in DCMS mode using an Ar pressure of 300 mPa and a substrate temperature of 400 °C. Such process parameters yielded coatings with a slightly higher density of 2.3 g/cm3, a B/C ratio of ~4, and the compressive residual stresses limited to 220 MPa.
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| 31. |
- Tholander, Christopher, et al.
(author)
-
Ab initio calculations and experimental study of piezoelectric YxIn1-xN thin films deposited using reactive magnetron sputter epitaxy
- 2016
-
In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 105, s. 199-206
-
Journal article (peer-reviewed)abstract
- 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.
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| 32. |
- Žukauskaitė, Agnė, et al.
(author)
-
Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films
- 2012
-
In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 111:9, s. 093527-
-
Journal article (peer-reviewed)abstract
- Piezoelectric wurtzite ScxAl1-xN (x=0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 °C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 °C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x≥0.2 when substrate temperature is increased from 400 to 800 °C. The piezoelectric response of epitaxial ScxAl1-xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x=0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.
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| 33. |
-
- 2019
-
Journal article (peer-reviewed)
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| 34. |
- Alami, Jones, et al.
(author)
-
Plasma dynamics in a highly ionized pulsed magnetron discharge
- 2005
-
In: Plasma sources science & technology. - : IOP Publishing. - 0963-0252 .- 1361-6595. ; 14:3, s. 525-531
-
Journal article (peer-reviewed)abstract
- We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.
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| 35. |
- Albani, Giorgia, et al.
(author)
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Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
- 2016
-
In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11
-
Journal article (peer-reviewed)abstract
- The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
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| 36. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
-
Effect of O/N content on the phase, morphology, and optical properties of titanium oxynitride thin films
- 2023
-
In: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 58, s. 10975-10985
-
Journal article (peer-reviewed)abstract
- Phase formation, morphology, and optical properties of Ti(O,N) thin films with varied oxygen-to- nitrogen ration content were investigated. The films were deposited by magnetron sputtering at 500°C on Si(100) and c-plane sapphire substrate. A competition between a NaCl B1 structure TiN1-xOx, a rhombohedral structure Ti2(O1-yNy)3, and an anatase structure Ti(O1-zNz)2 phase was observed. While the N-rich films were composed of a NaCl B1 TiN1-xOx phase, an increase of oxygen in the films yields the growth of rhombohedral Ti2(O1-yNy)3 phase and the oxygen-rich films are comprised of a mixture of the rhombohedral Ti2(O1-yNy)3 phase and anatase Ti(O1-zNz)2 phase. The optical properties of the films were correlated to the phase composition and the observation of abrupt changes in terms of refractive index and absorption coefficient. The oxide film became relatively transparent in the visible range while the addition of nitrogen into films increases the absorption. The oxygen rich-samples have bandgap values below 3.75 eV, which is higher than the value for pure TiO2, and lower than the optical bandgap of pure TiN. The optical properties characterizations revealed the possibility of adjusting the band gap and the absorption coefficient depending on the N-content, because of the phases constituting the films combined with anionic substitution.
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| 37. |
- Ali, Sharafat, 1976-, et al.
(author)
-
Modification of float glass surfaces by novel oxy-nitride thin films
- 2015
-
Reports (peer-reviewed)abstract
- Glass is indispensable and innovative material that has plenty of applications. It is an essential component of numerous products that we use every day, most often without noticing it. Glass is widely used in a variety of applications e.g. housing and buildings, automotive and transport, containers, drinking vessels, displays, insulation and optical fibers due to its universal forming ability, transparency, chemical durability, form stability, hardness relatively low price and possibility of recycling. Flat glass is a wide market of the glass industry and generally ninety percent of all flat glass produced worldwide is manufactured using the float forming process. There is a large market strive for thinner and stronger glass in order to reduce costs, save energy, and to find new applications.This study comprises the modification of flat/float glass surface by novel oxynitride thin films in the Mg-Si-O-N and Ca-Si-O-N systems prepared by RF magnetron sputtering technique. The aim of this work is to develop a novel process in order to improve the mechanical and optical properties of flat/float glass by deposition of external materials e.g. alkaline earth metals and nitrogen to the surface in a process with the obvious potential to be automatic in industrial processes. Both mechanical and optical properties of the glass surface have been improved by the deposition of thin films. The float glass surface modified with Mg-Si-O-N have high value of hardness of 20 GPa, elastic modulus of 175 GPa and refractive index value of 1.96 compare to the float glass having hardness of 7 GPa, elastic modulus of 72 GPa and refractive index of 1.50. The method presented here is anticipated to be used in production in the future and would make it possible to produce larger quantities of strong flat glass for smartphone, tablet covers and display technology to a considerably lower cost.
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| 38. |
- Ali, Sharafat, et al.
(author)
-
Novel transparent Mg-Si-O-N thin films with high hardness and refractive index
- 2016
-
In: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 131, s. 1-4
-
Journal article (peer-reviewed)abstract
- There is an increasing demand for glass materials with better mechanical and optical properties for display and electronic applications. This paper describes the deposition of novel thin films of Mg-Si-O-N onto float glass substrates. Amorphous thin films in the Mg-Si-O-N system with high nitrogen and magnesium contents were deposited by reactive RF magnetron co-sputtering from Mg and Si targets in Ar/N2/O2 gas mixtures. The thin films studied span an unprecedented range of compositions up to 45 at% Mg and 80 at% N out of cations and anions respectively. Thin films in the Mg-Si-O-N system were found to be homogeneous and transparent in the visible region. Mechanical properties like hardness (H) and reduced elastic modulus (Er) show high values, up to 21 GPa and 166 GPa respectively. The refractive index (1.87-2.00) increases with increasing magnesium and nitrogen contents.
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| 39. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
-
Optical and mechanical properties of amorphous Mg-Si-O-N thin films deposited by reactive magnetron sputtering
- 2019
-
In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 372:25, s. 9-15
-
Journal article (peer-reviewed)abstract
- In this work, amorphous thin films in Mg-Si-O-N system typically containing >15 at.% Mg and 35 at.% N were prepared in order to investigate especially the dependence of optical and mechanical properties on Mg composition. Reactive RF magnetron co-sputtering from magnesium and silicon targets were used for the deposition of Mg-Si-O-N thin films. Films were deposited on float glass, silica wafers and sapphire substrates in an Ar, N2 and O2 gas mixture. X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry, and nanoindentation were employed to characterize the composition, surface morphology, and properties of the films. The films consist of N and Mg contents up to 40 at.% and 28 at.%, respectively and have good adhesion to substrates and are chemically inert. The thickness and roughness of the films increased with increasing content of Mg. Both hardness (16–21 GPa) and reduced elastic modulus (120–176 GPa) are strongly correlated with the amount of Mg content. The refractive index up to 2.01 and extinction coefficient up to 0.18 were found to increase with Mg content. The optical band gap (3.1–4.3) decreases with increasing the Mg content. Thin film deposited at substrate temperature of 100 °C shows a lower value of hardness (10 GPa), refractive index (1.75), and higher values of reduced elastic modulus (124 GPa) as compared to the thin film deposited at 310 °C and 510 °C respectively, under identical synthesis parameters.
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| 40. |
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| 41. |
- Ali, Sharafat, 1976-, et al.
(author)
-
Synthesis and characterization of the mechanical and optical properties of Ca-Si-O-N thin films deposited by RF magnetron sputtering
- 2017
-
In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 315, s. 88-94
-
Journal article (peer-reviewed)abstract
- Ca-Si-O-N thin films were deposited on commercial soda-lime silicate float glass, silica wafers and sapphire substrates by RF magnetron co-sputtering from Ca and Si targets in an Ar/N-2/O-2 gas mixture. Chemical composition, surface morphology, hardness, reduced elastic modulus and optical properties of the films were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, nanoindentation, and spectroscopic ellipsometry. It was found that the composition of the films can be controlled by the Ca target power, predominantly, and by the reactive gas flow. Thin films in the Ca-Si-O-N system are composed of N and Ca contents up to 31 eq. % and 60 eq. %, respectively. The films thickness ranges from 600 to 3000 nm and increases with increasing Ca target power. The films surface roughness varied between 2 and 12 nm, and approximately decreases with increasing power of Ca target. The hardness (4-12 GPa) and reduced elastic modulus (65-145 GPa) of the films increase and decrease with the N and Ca contents respectively. The refractive index (1.56-1.82) is primarily dictated by the N content. The properties are compared with findings for bulk glasses in the Ca-Si-(Al)-O-N systems, and it is concluded that Ca-Si-O-N thin films have higher values of hardness, elastic modulus and refractive index than bulk glasses of similar composition. (C) 2017 Elsevier B.V. All rights reserved.
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| 42. |
- Ali, Sharafat, 1976-, et al.
(author)
-
Thin films in M-Si-O-N thin systems
- 2017
-
In: 44th International Conference on Metallurgical Coating and Thin Films (ICMCTF), San Diego, CA, USA, 24-28 Apr 2017.
-
Conference paper (peer-reviewed)
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| 43. |
- Alves Machado Filho, Manoel, et al.
(author)
-
Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations
- 2023
-
In: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 3:1, s. 84-93
-
Journal article (peer-reviewed)abstract
- By addressing precursor prevalence and energetics using the DFT-based synthetic growth concept (SGC), the formation mechanism of self-induced InAlN core–shell nanorods (NRs) synthesized by reactive magnetron sputter epitaxy (MSE) is explored. The characteristics of In- and Al-containing precursor species are evaluated considering the thermal conditions at a typical NR growth temperature of around 700 °C. The cohesive and dissociation energies of In-containing precursors are consistently lower than those of their Al-containing counterparts, indicating that In-containing precursors are more weakly bonded and more prone to dissociation. Therefore, In-containing species are expected to exhibit lower abundance in the NR growth environment. At increased growth temperatures, the depletion of In-based precursors is even more pronounced. A distinctive imbalance in the incorporation of Al- and In-containing precursor species (namely, AlN/AlN+, AlN2/AlN2+, Al2N2/Al2N2+, and Al2/Al2+ vs InN/InN+, InN2/InN2+, In2N2/In2N2+, and In2/In2+) is found at the growing edge of the NR side surfaces, which correlates well with the experimentally obtained core–shell structure as well as with the distinctive In-rich core and vice versa for the Al-rich shell. The performed modeling indicates that the formation of the core–shell structure is substantially driven by the precursors’ abundance and their preferential bonding onto the growing edge of the nanoclusters/islands initiated by phase separation from the beginning of the NR growth. The cohesive energies and the band gaps of the NRs show decreasing trends with an increment in the In concentration of the NRs’ core and with an increment in the overall thickness (diameter) of the NRs. These results reveal the energy and electronic reasons behind the limited growth (up to ∼25% of In atoms of all metal atoms, i.e., InxAl1–xN, x ∼ 0.25) in the NR core and may be qualitatively perceived as a limiting factor for the thickness of the grown NRs (typically <50 nm).
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| 44. |
- Aquila, Andrew L., et al.
(author)
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Measurements of the optical constants of scandium in the 50-1300 eV range
- 2004
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In: SPIE 5538, Optical Constants of Materials for UV to X-Ray Wavelengths. - : SPIE - International Society for Optical Engineering. ; , s. 64-71
-
Conference paper (peer-reviewed)abstract
- Scandium containing multilayers have been produced with very high reflectivity in the soft x-ray spectrum. Accurate optical constants are required in order to model the multilayer reflectivity. Since there are relatively few measurements of the optical constants of Scandium in the soft x-ray region we have performed measurements over the energy range of 50-1,300 eV. Thin films of Scandium were deposited by ion-assisted magnetron sputtering at Linkoping University and DC Magnetron sputtering at CXRO. Transmission measurements were performed at the Advanced Light Source beamline 6.3.2. The absorption coefficient was deduced from the measurements and the dispersive part of the index of refraction was obtained using the Kramers-Kronig relation. The measured optical constants are used to model the near-normal incidence reflectivity of Cr/Sc multilayers near the Sc L2,3 edge.
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| 45. |
- Arwin, Hans, 1950-, et al.
(author)
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Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry
- 2012
-
In: AES 2012, Advanced Electromagnetics Symposium.
-
Conference paper (other academic/artistic)abstract
- Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry H. Arwin*, T. Berlind, J. Birch, L. Fernandez Del Rio, J. Gustafson, J. Landin,R. Magnusson, C. Åkerlind, and K. JärrendahlDepartment of Physics, Chemistry and Biology, Linköping University, Sweden*corresponding author: han@ifm.liu.se Abstract- Many scarab beetles exhibit structural colors and complex polarization phenomena in reflection. These effects are characterized with spectroscopic Mueller-matrix ellipsometry in our work. The polarization ellipse of reflected light as well as the degree of polarization is presented including variations with angle of incidence and wavelength. Emphasis is on beetles showing chiral effects and structural modeling of cuticle nanostructure is discussed. Background Since one hundred years it is known that some scarab beetles reflect elliptically polarized light as demonstrated by Michelson for the beetle Chrysina resplendens [1]. The handedness of the polarization is in a majority of the cases left-handed but also right-handed polarization has been found [2,3]. The ellipticity varies with wavelength and viewing angle but can be close to +1 or -1 (right or left circular polarization, respectively) and in addition these beetles may exhibit beautiful structural colors. The polarization and color effects are generated in the outer part of the exoskeleton, the cuticle. These natural photonic structures are often multifunctional and play important roles for survival of beetles, e.g. for hiding from or scaring predators, for intraspecies communication, etc. [4]. However, such structures may find use in many commercial applications and a major motivation for detailed studies of natural photonic structures is that they inspire to biomimetic applications [5,6].Approach Our objective is to use spectral Mueller-matrix data on scarab beetles to parameterize reflection properties in terms of polarization parameters and degree of polarization. The studied beetles all are phytophagous and include species from the Cetoniinae subfamily (e.g. Cetonia aurata and Coptomia laevis,), the Rutelinae subfamily (e.g. Chrysina argenteola and Chrysina resplendens) and the Melolonthinae subfamily (Cyphochilus insulanus). Furthermore, structural modeling is presented on Cetonia aurata and a few more beetles to demonstrate that structural parameters can be extracted by advanced modeling of Mueller-matrix data.Experimental A dual rotating compensator ellipsometer (RC2, J. A. Woollam Co., Inc.) is used to record all 16 Mueller-matrix elements mij (i,j=1..4) in the spectral range 300 – 900 nm at angles of incidence in the range 20-70º. The elements are normalized to m11 and thus have values between -1 and +1. All measurements are performed on the scutellum (a small triangular part on the dorsal side of the beetles) with focusing optics resulting in a spot size of the order of 50-100 mm. The software CompleteEASE (J. A. Woollam Co., Inc.) is used for analysis.Results and discussion As an example, Fig. 1 shows contour plots of Mueller-matrix data measured on Cetonia aurata. This beetle has a metallic shine and if illuminated with unpolarized white light it reflects left-handed polarized green light as revealed by the non-zero Mueller-matrix elements m14 and m41 in the green spectral region for angles of incidence below about 45º. This is clearly seen in the graph to the right in Fig. 1 which shows a spectrum for Mueller-matrix element m41at 20º as well as fitted model data. A model based on a twisted lamella structure, also called Bouligand structure, is used to model the chiral nanostructure [4]. Given the complexity of the nanostructure, an excellent model fit is achieved. The obtained model parameters are the spectral variation of the refractive index of the birefringent lamellas and the pitch. The model also includes a dielectric surface layer. Fig.1. Left: Mueller-matrix data on Cetonia aurata. Each contour plot shows mij, where i and j correspond to the row and column, respectively. m11 =1 and is not shown but is replaced with a photo of the beetle. Right: Experimental and model-generated Mueller-matrix element m41at an angle of incidence of 20º. From the Mueller-matrix data one can also determine so called derived parameters including azimuth and ellipticity of the polarization ellipse and the degree of polarization. The variations of these parameters with angle of incidence are presented for a selection of scarab beetles. Examples of both left-handed and right-handed polarization effects are shown and the importance of degree of polarization will be discussed.Concluding remarks Mueller-matrix spectra at oblique incidence are very rich in information about reflection properties and allows parameterization of polarization parameters of the reflected light. Both left-handed and right-handed reflected light is found in scarab beetles. Mueller-matrix data can also be used for a detailed modeling of the nanostructure of the cuticle of beetles.AcknowledgementsFinancial support was obtained from the Knut and Alice Wallenberg foundation and the Swedish Research Council. The Museum of Natural History in Stockholm, the National Museum of Natural Science in Madrid, the Berlin Museum of Natural History and the Natural History Museum in London are acknowledged for loan of beetles. REFERENCESMichelson, A. A. “On Metallic Colouring in Birds and Insects,” Phil. Mag., 21, 554-567, 1911.Goldstein, D. H. “Polarization properties of Scarabaeidae,” Appl. Opt., 45, 7944-7950, 2006.Hodgkinson, I., Lowrey, S., Bourke, L., Parker, A. and McCall, M. W. “Mueller-matrix characterization of beetle cuticle polarized and unpolarized reflections from representative architectures,” Appl. Opt., 49, 4558-4567, 2010.Vukusic, P. and Sambles, J. R. “Photonic structures in biology,” Nature, 424, 852-855, 2003.Lenau, T. and Barfoed, M. “Colours and Metallic Sheen in Beetle Shells - A Biomimetic Search for Material Structuring Principles Causing Light Interference,” Adv. Eng. Mat., 10, 299-314. 2008.Parker, A. R. and Townley, H. E “Biomimetics of photonic nanostructures,” Nature Nanotech., 2, 347-351, 2007.
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| 46. |
- Backis, A., et al.
(author)
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Time- and energy-resolved effects in the boron-10 based multi-grid and helium-3 based thermal neutron detectors
- 2021
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In: Measurement science and technology. - : IOP PUBLISHING LTD. - 0957-0233 .- 1361-6501. ; 32:3
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Journal article (peer-reviewed)abstract
- The boron-10 based multi-grid detector is being developed as an alternative to helium-3 based neutron detectors. At the European Spallation Source, the detector will be used for time-of-flight neutron spectroscopy at cold to thermal neutron energies. The objective of this work is to investigate fine time- and energy-resolved effects of the Multi-Grid detector, down to a few mu eV, while comparing it to the performance of a typical helium-3 tube. Furthermore, it is to characterize differences between the detector technologies in terms of internal scattering, as well as the time reconstruction of similar to mu s short neutron pulses. The data were taken at the Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube were installed at the ESS test beamline, V20. Using a Fermi-chopper, the neutron beam of the reactor was chopped into a few tens of mu s wide pulses before reaching the detector, located a few tens of cm downstream. The data of the measurements show an agreement between the derived and calculated neutron detection efficiency curve. The data also provide fine details on the effect of internal scattering, and how it can be reduced. For the first time, the chopper resolution was comparable to the timing resolution of the Multi-Grid detector. This allowed a detailed study of time- and energy resolved effects, as well as a comparison with a typical helium-3 tube.
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| 47. |
- Bairagi, Samiran, et al.
(author)
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Formation of quaternary Zn(AlxGa1−x)2O4 epilayers driven by thermally induced interdiffusion between spinel ZnGa2O4 epilayer and Al2O3 substrate
- 2023
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In: Materials Today Advances. - : Elsevier. - 2590-0498. ; 20
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Journal article (peer-reviewed)abstract
- Zinc aluminogallate, Zn(AlxGa1−x)2O4 (ZAGO), a single-phase spinel structure, offers considerable potential for high-performance electronic devices due to its expansive compositional miscibility range between aluminum (Al) and gallium (Ga). Direct growth of high-quality ZAGO epilayers however remains problematic due to the high volatility of zinc (Zn). This work highlights a novel synthesis process for high-quality epitaxial quaternary ZAGO thin films on sapphire substrates, achieved through thermal annealing of a ZnGa2O4 (ZGO) epilayer on sapphire in an ambient air setting. In-situ annealing x-ray diffraction measurements show that the incorporation of Al in the ZGO epilayer commenced at 850 °C. The Al content (x) in ZAGO epilayer gradually increased up to around 0.45 as the annealing temperature was raised to 1100 °C, which was confirmed by transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy. X-ray rocking curve measurement revealed a small full width at half maximum value of 0.72 °, indicating the crystal quality preservation of the ZAGO epilayer with a high Al content. However, an epitaxial intermediate �–(AlxGa1−x)2O3 layer (� - AGO) was formed between the ZAGO and sapphire substrate. This is believed to be a consequence of the interdiffusion of Al and Ga between the ZGO thin film and sapphire substrate. Using density functional theory, the substitution cost of Ga in sapphire was determined to be about 0.5 eV lower than substitution cost of Al in ZGO. Motivated by this energetically favorable substitution, a formation mechanism of the ZAGO and AGO layers was proposed. Spectroscopic ellipsometry studies revealed an increase in total thickness of the film from 105.07 nm (ZGO) to 147.97 nm (ZAGO/AGO) after annealing to 1100 °C, which were corroborated using TEM. Furthermore, an observed increase in the direct (indirect) optical bandgap from 5.06 eV (4.7 eV) to 5.72 eV (5.45 eV) with an increasing Al content in the ZAGO layer further underpins the formation of a quaternary ZAGO alloy with a tunable composition.
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| 48. |
- Bairagi, Samiran, et al.
(author)
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Glancing Angle Deposition and Growth Mechanism of Inclined AlN Nanostructures Using Reactive Magnetron Sputtering
- 2020
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In: Coatings. - : MDPI. - 2079-6412. ; 10:8
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Journal article (peer-reviewed)abstract
- Glancing angle deposition (GLAD) of AlN nanostructures was performed at room temperature by reactive magnetron sputtering in a mixed gas atmosphere of Ar and N-2. The growth behavior of nanostructures shows strong dependence on the total working pressure and angle of incoming flux. In GLAD configuration, the morphology changed from coalesced, vertical nanocolumns with faceted terminations to highly inclined, fan-like, layered nanostructures (up to 38 degrees); while column lengths decreased from around 1743 to 1068 nm with decreasing pressure from 10 to 1.5 mTorr, respectively. This indicates a change in the dominant growth mechanism from ambient flux dependent deposition to directional ballistic shadowing deposition with decreasing working pressures, which is associated with the change of energy and incident angle of incoming reactive species. These results were corroborated using simulation of metal transport (SiMTra) simulations performed at similar working pressures using Ar and N separately, which showed the average particle energy and average angle of incidence decreased while the total average scattering angle of the metal flux arriving at substrate increased with increasing working pressures. Observing the crystalline orientation of GLAD deposited wurtzite AlN nanocolumns using X-ray diffraction (XRD), pole-figure measurements revealedc-axis growth towards the direction of incoming flux and a transition from fiber-like to biaxial texture took place with increasing working pressures. Under normal deposition conditions, AlN layer morphology changed from {0001} to {10 (1) over bar1} with increasing working pressure because of kinetic energy-driven growth.
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| 49. |
- Bairagi, Samiran, et al.
(author)
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Zinc gallate (ZnGa2O4) epitaxial thin films : determination of optical properties and bandgap estimation using spectroscopic ellipsometry
- 2022
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In: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 12:8, s. 3284-3295
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Journal article (peer-reviewed)abstract
- Electronic grade ZnGa2O4 epitaxial thin films were grown on c-plane sapphire substrates by metal-organic chemical vapor deposition and investigated using spectroscopic ellipsometry. Their thickness, roughness and optical properties were determined using a Multiple Sample Analysis based approach by the regression analysis of optical model and measured data. These samples were then compared to samples which had undergone ion etching, and it was observed that etching time up to four minutes had no discernible impact on its optical properties. Line shape analysis of resulting absorption coefficient dispersion revealed that ZnGa(2)O(4 )exhibited both direct and indirect interband transitions. The modified Cody formalism was employed to determine their optical bandgaps. These values were found to be in good agreement with values obtained using other popular bandgap extrapolation procedures. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.
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| 50. |
- Bakhit, Babak, et al.
(author)
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Microstructure, mechanical, and corrosion properties of Zr1-xCrxBy diboride alloy thin films grown by hybrid high power impulse/DC magnetron co-sputtering
- 2022
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In: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 591
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Journal article (peer-reviewed)abstract
- We study microstructure, mechanical, and corrosion properties of Zr1-xCrxBy coatings deposited by hybrid high power impulse/DC magnetron co-sputtering (CrB2-HiPIMS/ZrB2-DCMS). Cr/(Zr + Cr) ratio, x, increases from 0.13 to 0.9, while B/(Zr + Cr) ratio, y, decreases from 2.92 to 1.81. As reference, ZrB2.18 and CrB1.81 layers are grown at 4000 W DCMS. ZrB2.18 and CrB1.81 columns are continual from near substrate toward the surface with open column boundaries. We find that the critical growth parameter to achieve dense films is the ratio of Cr+- dominated ion flux and the (Zr + B) neutral flux from the ZrB2 target. Thus, the alloys are categorized in two groups: films with x < 0.32 (low Cr+/(Zr + B) ratios) that have continuous columnar growth, rough surfaces, and open column boundaries, and films with x >= 0.32 (high Cr+/(Zr + B) ratios) that Cr+-dominated ion fluxes are sufficient to interrupt continuous columns, resulting in smooth surface and dense fine-grain microstructure. The pulsed metal-ion irradiation is more effective in film densification than continuous Ar+ bombardment. Dense Zr0.46Cr0.54B2.40 and Zr0.10Cr0.90B1.81 alloys are hard (> 30 GPa) and almost stress-free with relative nano indentation toughness of 1.3 MPa root m and 2.3 MPa root m, respectively, and remarkedly low corrosion rates (~& nbsp;1.0 x 10(-6) mA/cm(2) for Zr0.46Cr0.54B2.40 and~& nbsp; 2.1 x 10(-6) mA/cm(2) for Zr0.10Cr0.90B1.81).
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