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Sökning: WFRF:(Palisaitis J.)

  • Resultat 1-10 av 13
  • [1]2Nästa
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1.
  • Mockute, A., et al. (författare)
  • Age hardening in (Ti1-xAlx)B2+Delta thin films
  • 2017
  • Ingår i: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 127, s. 122-126
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin films of (Ti0.71Al0.29)B2+1.08 have been deposited by magnetron sputtering. Post-deposition annealing at 1000 degrees C for 1 h results in increased hardness and elastic modulus, from 32 to 37 GPa and from 436 to 461 GPa, respectively. In both as-deposited and annealed states the films adhere well to the substrate, indicating no considerable internal stress. The initial high hardness is attributed to a columnar microstructure consisting of crystalline (Ti,Al)B-2 columns separated by an amorphous B matrix. The observed age hardening corresponds to phase separation within the (Ti,Al)B-2 columns including the formation of Ti-deficient crystallites within the grain interior upon annealing.
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2.
  • Mockute, A., et al. (författare)
  • Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering
  • 2019
  • Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 669, s. 181-187
  • Tidskriftsartikel (refereegranskat)abstract
    • (Ti1-xAlx)B2+Delta films with a lateral composition gradient of x = [0.30-0.66] and Delta = [0.07-1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 degrees C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.
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3.
  • Magnus, Fridrik, et al. (författare)
  • Sequential magnetic switching in Fe/MgO(001) superlattices
  • 2018
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 97:17
  • Tidskriftsartikel (refereegranskat)abstract
    • Polarized neutron reflectometry is used to determine the sequence of magnetic switching in interlayer exchangecoupled Fe/MgO(001) superlattices in an applied magnetic field. For 19.6 Å thick MgO layers we obtain a 90◦periodic magnetic alignment between adjacent Fe layers at remanence. In an increasing applied field the toplayer switches first followed by its second-nearest neighbor. For 16.4 Å MgO layers, a 180◦periodic alignment isobtained at remanence and with increasing applied field the layer switching starts from the two outermost layersand proceeds inwards. This sequential tuneable switching opens up the possibility of designing three-dimensionalmagnetic structures with a predefined discrete switching sequence
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4.
  • Malinovskis, Paulius, et al. (författare)
  • Synthesis and characterisation of Mo-B-C thin films deposited by non-reactive DC magnetron sputtering
  • 2017
  • Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 309, s. 506-515
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin films in the Mo-B-C system with varying carbon content (up to 37 at.%) were deposited using non-reactive DC magnetron sputtering. The phase composition and microstructure were determined and the potential use of the films in sliding electrical contact applications was evaluated. Films with lower than 23 at.% carbon content consisted of nanocrystalline MoB2 - x grains surrounded by an amorphous tissue phase (a-B for binary, and a-BCx for ternary films). With increasing carbon content grain sizes was found to decrease (from 16 to 5 nm), and above 23 at.% carbon the films deposited at room temperature were X-ray amorphous. Scanning transmission electron microscopy and energy dispersive X-ray spectroscopy reveal that these films contain Mo-rich and Mo-poor regions, and thus are two-phase amorphous nanocomposites. Low-carbon content samples exhibited a friction coefficient against the steel counter surface of 1.1; this was reduced to 0.8 for high carbon-content films. Analysis of the tribofilm revealed formation of molybdenum oxide and amorphous carbon, however without significant lubricating effect at room temperature. Hardness and elastic modulus decrease with carbon content from similar to 29 to similar to 22 GPa and similar to 526 to similar to 326 GPa. These values give an WE ratio of 0.06 to 0.07, indicating brittle material. Resistivity was found to increase with carbon content from similar to 175 mu Omega cm for binary Mo-B to similar to 395 mu Omega cm for Mo-B-C thin film with 37 at.% of C. Therefore all the above results suggest that the Mo-B-C films are not suitable for sliding electrical contacts.
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5.
  • Moubah, Reda, et al. (författare)
  • Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices
  • 2016
  • Ingår i: Physical Review Applied. - : American physical society. - 2331-7019. ; 5:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a discrete layer-by-layer magnetic switching in Fe/MgO superlattices driven by an antiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunneling through MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgO thickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropy stabilizes both 90 degrees and 180 degrees periodic alignment of adjacent layers throughout the entire superlattice. The tunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe/MgO/Fe junctions, is an appealing combination for three-dimensional spintronic memories and logic devices.
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6.
  • Bakhit, Babak, et al. (författare)
  • Age hardening in superhard ZrB2-rich Zr1-xTaxBy thin films
  • 2021
  • Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 191, s. 120-125
  • Tidskriftsartikel (refereegranskat)abstract
    • We recently showed that sputter-deposited Zr1-xTaxBy thin films have hexagonal AlB2-type columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. As-deposited layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we study the mechanical properties of ZrB2.4, Zr0.8Ta0.2B1.8, and Zr0.7Ta0.3B1.5 films annealed in Ar atmosphere as a function of annealing temperature Ta up to 1200 °C. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to Ta = 800 °C, with the highest hardness achieved for Zr0.8Ta0.2B1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at Ta > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire Ta range.
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7.
  • Halim, Joseph, 1985-, et al. (författare)
  • Synthesis of Two-Dimensional Nb1.33C (MXene) with Randomly Distributed Vacancies by Etching of the Quaternary Solid Solution (Nb2/3Sc1/3)2AlC MAX Phase
  • 2018
  • Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 1:6, s. 2455-2460
  • Tidskriftsartikel (refereegranskat)abstract
    • Introducing point defects in two-dimensional (2D) materials can alter or enhance their properties. Here, we demonstrate how etching a laminated (Nb2/3Sc1/3)2AlC MAX phase (solid solution) of both the Sc and Al atoms results in a 2D Nb1.33C material (MXene) with a large number of vacancies and vacancy clusters. This method is applicable to any quaternary, or higher, MAX phase, wherein one of the transition metals is more reactive than the other and could be of vital importance in applications such as catalysis and energy storage. We also report, for the first time, on the existence of solid solution (Nb2/3Sc1/3)3AlC2 and (Nb2/3Sc1/3)4AlC3 phases.
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8.
  • Junaid, Muhammad, et al. (författare)
  • Epitaxial Growth of GaN (0001)/Al2O3 (0001) by Reactive High Power Impulse Magnetron Sputter Deposition
  • Annan publikation (övrigt vetenskapligt)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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9.
  • Muhammad, Junaid, et al. (författare)
  • Two-domain formation during the epitaxial growth of GaN (0001) on c-plane Al2O3 (0001) by high power impulse magnetron sputtering
  • 2011
  • Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 110:12, s. 123519-
  • Tidskriftsartikel (refereegranskat)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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10.
  • Nedfors, Nils, et al. (författare)
  • The influence of pressure and magnetic field on the deposition of epitaxial TiBx thin films from DC magnetron sputtering
  • 2020
  • Ingår i: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 177
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetron sputter deposition of TiBx thin films from a TiB2 target typically results in highly overstoichiometric films due to differences in sputtered-atom ejection angles and gas-phase scattering during transport to the substrate. This study investigates the effects of the magnetron magnetic field strength at the substrate position and the Ar sputtering pressure on the resulting film composition and crystalline quality. It is shown that the B/Ti atomic ratio can be reduced from 2.7 to 2.1 by increasing the Ar pressure from 5 mTorr to 20 mTorr, a trend consistent with previous work. Despite the use of a relatively high Ar pressure, a change to a stronger outer magnetic pole leads to, dense TiB2.1 films of high crystal quality, as shown by X-ray diffraction, scanning transmission electron microscopy, and specific resistivity of 32 mu Omega cm. For epitaxial films deposited at 900 degrees C on Al2O3(001), a TiB2[110]//Al2O3[100] orientational relationship were obtained.
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  • Resultat 1-10 av 13
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