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  • 151.
    Ghafoor, Naureen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Klenov, Dmitri O.
    FEI Co, Netherlands.
    Freitag, Bert
    FEI Co, Netherlands.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Self-organized anisotropic (Zr1-xSix)N-y nanocomposites grown by reactive sputter deposition2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 82, p. 179-189Article in journal (Refereed)
    Abstract [en]

    The physical properties of hard and superhard nanocomposite thin films are strongly dependent on their nanostructure. Here, we present the results of an investigation of nanostructural evolution and the resulting mechanical properties of (Zr1-xSix)N-y films, with 0 less than= x less than= 1 and 1 less than= y less than= 1.27, grown on MgO(0 0 1) and Al2O3(0 0 0 1) substrates at temperatures T-s = 500-900 degrees C by reactive magnetron sputter deposition from Zr and Si targets. X-ray diffraction and transmission electron microscopy (TEM) results show that there is a T-s/composition window in which stoichiometric Zr-Si-N and amorphous a-Si3N4 phases mutually segregate and self-organize into encapsulated 3-5 um wide ZrN-rich (Zr1-xSix)N columns which extend along the growth direction with a strong (002) texture. Lattice-resolved scanning TEM and energy-dispersive X-ray spectroscopy reveal that the (Zr1-xSix)N-y nanocolumns are separated by a bilayer tissue phase consisting of a thin crystalline SiNy-rich (Zr1-xSix)N-y layer with an a-Si3N4 overlayer. Incorporation of metastable SiN into NaCl-structure ZrN leads to an enhanced nanoindentation hardness H which is a function of T-s and film composition. For nanocomposites with composition (Zr(0.8)Sio(0.2))N-1.14 (10 at.% Si) H, increases from 26 GPa at 500 degrees C to 37 GPa at 900 degrees C. For comparison, the hardness of epitaxial ZrN/MgO(0 0 1) layers grown at T-s = 800 degrees C is 24 GPa. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 152.
    Hänninen, Tuomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Silicon oxynitride films deposited by reactive high power impulse magnetron sputtering using nitrous oxide as a single-source precursor2015In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 33, no 5, p. 05E121-Article in journal (Refereed)
    Abstract [en]

    Silicon oxynitride thin films were synthesized by reactive high power impulse magnetron sputtering of silicon in argon/nitrous oxide plasmas. Nitrous oxide was employed as a single-source precursor supplying oxygen and nitrogen for the film growth. The films were characterized by elastic recoil detection analysis, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray reflectivity, scanning electron microscopy, and spectroscopic ellipsometry. Results show that the films are silicon rich, amorphous, and exhibit a random chemical bonding structure. The optical properties with the refractive index and the extinction coefficient correlate with the film elemental composition, showing decreasing values with increasing film oxygen and nitrogen content. The total percentage of oxygen and nitrogen in the films is controlled by adjusting the gas flow ratio in the deposition processes. Furthermore, it is shown that the film oxygen-to-nitrogen ratio can be tailored by the high power impulse magnetron sputtering-specific parameters pulse frequency and energy per pulse. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

  • 153.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. European Spallat Source ESS AB, Sweden.
    Zeitelhack, Karl
    Technical University of Munich, Germany.
    Kudejova, Petra
    Technical University of Munich, Germany.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, Richard
    European Spallat Source ESS AB, Sweden; Mid Sweden University, Sweden.
    Stability of (B4C)-B-10 thin films under neutron radiation2015In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 113, p. 14-19Article in journal (Refereed)
    Abstract [en]

    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.

  • 154.
    Žukauskaitė, Agnė
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Fraunhofer Institute for Applied Solid State Physics, Freiburg, Germany.
    Tholander, Christopher
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pališaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stabilization of Wurtzite Sc0.4Al0.6N in Pseudomorphic Epitaxial ScxAl1-xN/InyAl1-yN Superlattices2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 94, p. 101-110Article in journal (Refereed)
    Abstract [en]

    Pseudomorphic stabilization in wurtzite ScxAl1-xN/AlN and ScxAl1-xN/InyAl1-yN superlattices (x=0.2, 0.3, and 0.4; y=0.2-0.72), grown by reactive magnetron sputter epitaxy was investigated. X-ray diffraction and transmission electron microscopy show that in ScxAl1-xN/AlN superlattices the compressive biaxial stresses due to positive lattice mismatch in Sc0.3Al0.7N and Sc0.4Al0.6N lead to loss of epitaxy, although the structure remains layered. For the negative lattice mismatched In-rich ScxAl1-xN/InyAl1-yN superlattices a tensile biaxial stress promotes the stabilization of wurtzite ScxAl1-xN even for the highest investigated concentration x=0.4. Ab initio calculations with fixed in-plane lattice parameters show a reduction in mixing energy for wurtzite ScxAl1-xN under tensile stress when x≥0.375 and support the experimental results.

  • 155.
    Tengdelius, Lina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chubarov, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Stoichiometric, epitaxial ZrB2 thin films with low oxygen-content deposited by magnetron sputtering from a compound target: Effects of deposition temperature and sputtering power2015In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 430, p. 55-62Article in journal (Refereed)
    Abstract [en]

    Zirconium diboride (ZrB2) thin films have been deposited on 4H-SiC(0001) substrates by direct current magnetron sputtering from a compound target. The effect of deposition temperature (500-900 degrees C) and sputtering power (100-400 W) on the composition and structure of the films have been investigated. Electron microscopy and X-ray diffraction reveal that high sputtering power values and high deposition temperatures are favorable to enhance the crystalline order of the epitaxial 0001 oriented films. X-ray photoelectron spectroscopy shows that the composition of the films is near-stoichiometric for all deposition temperatures and for high sputtering power values of 300 W and 400 W, whereas under-stoichiometric films arc obtained when applying 100 W or 200 W. Decreasing the deposition temperature, or in particular the sputtering power, result in higher C and O impurity levels. The resistivity of the films was evaluated by four-point-probe measurements and found to scale with the amount of O impurities in the films. The lowest resistivity value obtained is 130 mu Omega cm, which makes the ZrB2 films interesting as an electrical contact material. (C) 2015 Elsevier B.V. All rights reserved.

  • 156.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA; Department of Physics, University of Illinois, Urbana, USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Strategy for tuning the average charge state of metal ions incident at the growing film during HIPIMS deposition2015In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 116, p. 36-41Article in journal (Refereed)
    Abstract [en]

    Energy and time-dependent mass spectrometry is used to determine the relative number density of singly- and multiply-charged metal-ion fluxes incident at the substrate during high-power pulsed magnetron sputtering (HIPIMS) as a function of the average noble-gas ionization potential. Ti is selected as the sputtering target since the microstructure, phase composition, properties, and stress-state of Ti-based ceramic thin films grown by HIPIMS are known to be strongly dependent on the charge state of Tin+ (n = 1, 2, …) ions incident at the film growth surface. We find that the flux of Tin+ with n > 2 is insignificant; thus, we measure the Ti2+/Ti+ integrated flux ratio JTi2+ =JTi+ at the substrate position as a function of the choice of noble gase Ne, Ar, Kr, Xe, as well as Ne/Ar, Kr/Ar, and Xe/Ar mixtures – supporting the plasma. We demonstrate that by changing noble-gas mixtures, JTi2+ varies by more than two orders of magnitude with only a small change in JTi+ . This allows the ratio JTi2+ =JTi+ to be continuously tuned from less than 0.01 with Xe, which has a low first-ionization potential IP1, to 0.62 with Ne which has a high IP1. The value for Xe, IP1Xe= 12.16 eV, is larger than the first ionization potential of Ti, IP1Ti= 6.85 eV, but less than the second Ti ionization potential, IP2Ti= 13.62 eV. For Ne, however, IP1Ne= 21.63 eV is greater than both IP1Ti and IP2Ti. Therefore, the high-energy tail of the plasma-electron energy distribution can be systematically adjusted, allowing JTi2+/JTi+ to be controllably varied over a very wide range.

  • 157.
    Lai, Chung-Chuan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Meshkian, Rahele
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dahlqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Näslund, Lars-Åke
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rivin, O.
    Nucl Research Centre Negev, Israel.
    Caspi, E. N.
    Nucl Research Centre Negev, Israel.
    Ozeri, O.
    Soreq Nucl Research Centre, Israel.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Structural and chemical determination of the new nanolaminated carbide Mo2Ga2C from first principles and materials analysis2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 99, p. 157-164Article in journal (Refereed)
    Abstract [en]

    Following our recent discovery of a new nanolaminated carbide, Mo2Ga2C, we herein present a detailed structural and chemical analysis of this phase based on ab initio calculations, X-ray photoelectron spectroscopy, high resolution scanning transmission electron microscopy, and neutron powder diffraction. Calculations suggest an energetically and dynamically stable structure for C in the octahedral sites between the Mo layers, with Ga bilayers - stacked in a simple hexagonal arrangement - between the Mo2C layers. The predicted elastic properties are below those of the related nanolaminate Mo2GaC. The predicted structure, including lattice parameters and atomic positions, is experimentally confirmed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 158.
    Serban, Alexandra
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Poenaru, Iuliana
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Junaid, Junaid
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Structural and compositional evolutions of InxAl1-xN core-shell nanorods grown on Si(111) substrates by reactive magnetron sputter epitaxy2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 21, p. 215602-Article in journal (Refereed)
    Abstract [en]

    Catalystless growth of InxAl1-xN core-shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The samples were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl1-xN nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core-shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl1-xN film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl1-xN is traced to the initial stage, showing that the formation of the core-shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl1-xN[0001]//Si[111] and InxAl1-xN[11 (2) over bar0]//Si[1 (1) over bar0] by removing the native SiOx layer from the substrate.

  • 159.
    Furlan, Andrej
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Structure and bonding in amorphous iron carbide thin films2015In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 4, p. 045002-Article in journal (Refereed)
    Abstract [en]

    We investigate the amorphous structure, chemical bonding, and electrical properties ofmagnetron sputtered Fe1−xCx (0.21 < x < 0.72) thin films. X-ray, electron diffraction andtransmission electron microscopy show that the Fe1−xCx films are amorphousnanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeCy , and acarbon-rich matrix. Pair distribution function analysis indicates a close-range order similar tothose of crystalline Fe3C carbides in all films with additional graphene-like structures at highcarbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we findthat the amorphous carbidic phase has a composition of 15–25 at% carbon that slightlyincreases with total carbon content. X-ray absorption spectra exhibit an increasing number ofunoccupied 3d states and a decreasing number of C 2p states as a function of carbon content.These changes signify a systematic redistribution in orbital occupation due to charge-transfereffects at the domain-size-dependent carbide/matrix interfaces. The four-point proberesistivity of the Fe1−xCx films increases exponentially with carbon content from ∼200μcm(x = 0.21) to ∼1200μcm (x = 0.72), and is found to depend on the total carbon contentrather than the composition of the carbide. Our findings open new possibilities for modifyingthe resistivity of amorphous thin film coatings based on transition metal carbides through thecontrol of amorphous domain structures.

  • 160.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    The dynamics of TiNx (x = 1 – 3) admolecule interlayer and intralayer transport on TiN/TiN(001) islands2015In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 589, p. 133-144Article in journal (Refereed)
    Abstract [en]

    It has been shown both experimentally and by density functional theory calculations that the primary diffusing species during the epitaxial growth of TiN/TiN(001) are Ti and N adatoms together with TiNx complexes (x = 1, 2, 3), in which the dominant N-containing admolecule species depends upon the incident N/Ti flux ratio. Here, we employ classical molecular dynamics (CMD) simulations to probe the dynamics of TiNx (x = 1–3) admolecules on 8 × 8 atom square, single-atom-high TiN islands on TiN(001), as well as pathways for descent over island edges. The simulations are carried out at 1000 K, a reasonable epitaxial growth temperature. We find that despite their lower mobility on infinite TiN(001) terraces, both TiN and TiN2 admolecules funnel toward descending steps and are incorporated into island edges more rapidly than Ti adatoms. On islands, TiN diffuses primarily via concerted translations, but rotation is the preferred diffusion mechanism on infinite terraces. TiN2 migration is initiated primarily by rotation about one of the N admolecule atoms anchored at an epitaxial site. TiN admolecules descend from islands by direct hopping over edges and by edge exchange reactions, while TiN2 trimers descend exclusively by hopping. In contrast, TiN3 admolecules are essentially stationary and serve as initiators for local island growth. Ti adatoms are the fastest diffusing species on infinite TiN(001) terraces, but on small TiN/TiN(001) islands, TiN dimers provide more efficient mass transport. The overall results reveal the effect of the N/Ti precursor flux ratio on TiN(001) surface morphological evolution and growth modes.

  • 161.
    Anasori, Babak
    et al.
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Xie, Yu
    Oak Ridge National Lab, TN 37831 USA.
    Beidaghi, Majid
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hosler, Brian C.
    Drexel University, PA 19104 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kent, Paul R. C.
    Oak Ridge National Lab, TN 37831 USA; Oak Ridge National Lab, TN 37831 USA.
    Gogotsi, Yury
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Barsoum, Michel W.
    Drexel University, PA 19104 USA.
    Two-Dimensional, Ordered, Double Transition Metals Carbides (MXenes)2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 10, p. 9507-9516Article in journal (Refereed)
    Abstract [en]

    The higher the chemical diversity and structural complexity of two-dimensional (2D) materials, the higher the likelihood they possess unique and useful properties. Herein, density functional theory (DFT) is used to predict the existence of two new families of 2D ordered, carbides (MXenes), MM-2 C-2 and MM-2 C-2(3), where M and M are two different early transition metals. In these solids, M layers sandwich M" carbide layers. By synthesizing Mo2TiC2Tx, Mo2Ti2C3Tx, and Cr2TiC2Tx (where T is a surface termination), we validated the DFT predictions. Since the Mo and Cr atoms are on the outside, they control the 2D flakes chemical and electrochemical properties. The latter was proven by showing quite different electrochemical behavior of Mo2TiC2Tx and Ti3C2Tx. This work further expands the family of 2D materials, offering additional choices of structures, chemistries, and ultimately useful properties.

  • 162.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bolz, S.
    CemeCon AG, Germany.
    Koelker, W.
    CemeCon AG, Germany.
    Schiffers, Ch.
    CemeCon AG, Germany.
    Lemmer, O.
    CemeCon AG, Germany.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    A review of metal-ion-flux-controlled growth of metastable TiAlN by HIPIMS/DCMS co-sputtering2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 257, p. 15-25Article in journal (Refereed)
    Abstract [en]

    We review results on the growth of metastable Ti1-xAlxN alloy films by hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) using the time domain to apply substrate bias either in synchronous with the entire HIPIMS pulse or just the metal-rich portion of the pulse in mixed Ar/N-2 discharges. Depending upon which elemental target, Ti or Al, is powered by HIPIMS, distinctly different film-growth kinetic pathways are observed due to charge and mass differences in the metal-ion fluxes incident at the growth surface. Al+ ion irradiation during Al-HIPIMS/Ti-DCMS at 500 degrees C, with a negative substrate bias V-s = 60 V synchronized to the HIPIMS pulse (thus suppressing Ar+ ion irradiation due to DCMS), leads to single-phase NaCl-structure Ti1-xAlxN films (x less than= 0.60) with high hardness (greater than30 GPa with x greater than 0.55) and low stress (0.2-0.8 GPa compressive). Ar+ ion bombardment can be further suppressed in favor of predominantly Al+ ion irradiation by synchronizing the substrate bias to only the metal-ion-rich portion of the Al-HIPIMS pulse. In distinct contrast Ti-HIPIMS/Al-DCMSTi1-xAlxN layers grown with Ti+/Ti2+ metal ion irradiation and the same HIPIMS-synchronized V-s value, are two-phase mixtures, NaCl-structure Ti1-xAlxN plus wurtzite AlN, exhibiting low hardness (similar or equal to 18 GPa) with high compressive stresses, up to -3.5 GPa. In both cases, film properties are controlled by the average metal-ion momentum per deposited atom less thanp(d)greater than transferred to the film surface. During Ti-HIPIMS, the growing film is subjected to an intense flux of doubly-ionized Ti2+, while Al2+ irradiation is insignificant during Al-HIPIMS. This asymmetry is decisive since the critical less thanp(d)greater than limit for precipitation of w-AlN, 135 [eV-amu](1/2), is easily exceeded during Ti-HIPIMS, even with no intentional bias. The high Ti2+ ion flux is primarily due to the second ionization potential (IP2) of Ti being lower than the first IP (IP1) of Ar. New results involving the HIPIMS growth of metastable Ti1-xAlxN alloy films from segmented TiAl targets are consistent with the above conclusions.

  • 163.
    Sangiovanni, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Edström, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ab-initio and classical molecular dynamics simulations of N2 desorption from TiN(001) surfaces2014In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 624, p. 25-31Article in journal (Refereed)
    Abstract [en]

    Ab initio molecular dynamics simulations based on density functional theory show that N adatoms are chemisorbed in threefold sites close to a N surface atom and between the two diagonally opposed neighboring Ti surface atoms on TiN(001). The most probable N adatom reaction pathway, even in the presence of nearby N adatoms, is for the N adatom and N surface atom pair to first undergo several exchange reactions and then desorb as a N2 molecule, resulting in a surface anion vacancy, with an activation barrier Edes of 1.37 eV and an attempt frequency Ades = 3.4 × 1013 s− 1. Edes is essentially equal to the N adatom surface diffusion barrier, Es = 1.39 eV, while As is only three to four times larger than Ades, indicating that isolated N adatoms migrate for only short distances prior to N2 desorption. The probability of N2 desorption via recombination of N adatoms on TiN(001) is much lower due to repulsive adatom/adatom interactions at separations less than ~ 3 Å which rapidly increase to ~ 2 eV at a separation of 1.5 Å. We obtain good qualitative and quantitative agreement with the above results using the modified embedded atom method potential to perform classical molecular dynamics simulations.

  • 164.
    Broitman, Esteban
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Advanced Carbon-Based Coatings2014In: Comprehensive Materials Processing, Elsevier, 2014, 4, p. 389-412Chapter in book (Refereed)
    Abstract [en]

    This chapter focuses on the development of alloyed diamondlike coatings, in particular a new class of fullerene-like (FL) materials. We describe unique resilient FL compounds by self-organization of nano-curved sp2-hybridized carbon features, with tuned mechanical and surface energy properties. These unique resilient materials consist of bent and intersecting hexagonal basal planes, fabricated by the incorporation of odd-member rings. Cross-linking enables the material to extend the strength of the covalently 2D hexagonal graphene network into 3D. The microstructural properties of three types of coatings, which have the possibility to be applied on a large scale, are described: carbon nitride, phosphorous carbide, and carbon fluoride.

  • 165.
    Khromov, Sergey
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Gregorius, D.
    Institut für Oberflächen- und Schichtanalytik IFOS GmbH, Kaiserslautern, Germany.
    Schiller, R.
    Institut für Oberflächen- und Schichtanalytik IFOS GmbH, Kaiserslautern, Germany.
    Lösch, J.
    Institut für Oberflächen- und Schichtanalytik IFOS GmbH, Kaiserslautern, Germany.
    Wahl, M.
    Institut für Oberflächen- und Schichtanalytik IFOS GmbH, Kaiserslautern, Germany.
    Kopnarski, M.
    Institut für Oberflächen- und Schichtanalytik IFOS GmbH, Kaiserslautern, Germany.
    Amano, A.
    Department of Electrical Engineering and Computer Science, Nagoya University, Chikusaku, Japan.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Atom probe tomography study of Mg doped GaN layers2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 27, p. 275701-Article in journal (Refereed)
    Abstract [en]

    Atom probe tomography studies on highly Mg-doped GaN(0001) layers with concentrations 5×1019 cm-3 and 1×1020 cm-3 were performed. Mg cluster formation was observed only in the higher doped sample whereas in the lower doped sample the Mg distribution was homogeneous. CL measurements showed that the emission normally attributed to stacking faults was only present in the lower doped layers ([Mg] = 1.5×1019 and 5×1019 cm-3), but absent in the higher-doped layer, where Mg clusters were detected. Mg clusters are proposed to produce a screening effect thereby destroying the exciton binding on the SFs thus rendering them optically inactive.

  • 166.
    Tamm, Aile
    et al.
    University of Tartu, Estonia .
    Kozlova, Jekaterina
    University of Tartu, Estonia .
    Aarik, Lauri
    University of Tartu, Estonia .
    Aidla, Aleks
    University of Tartu, Estonia .
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Kiisler, Alma-Asta
    University of Tartu, Estonia .
    Kasikov, Aarne
    University of Tartu, Estonia .
    Ritslaid, Peeter
    University of Tartu, Estonia .
    Maendar, Hugo
    University of Tartu, Estonia .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sammelselg, Vaeino
    University of Tartu, Estonia University of Tartu, Estonia .
    Kukli, Kaupo
    University of Tartu, Estonia University of Helsinki, Finland .
    Aarik, Jaan
    University of Tartu, Estonia .
    Atomic layer deposition of ZrO2 for graphene-based multilayer structures: In situ and ex situ characterization of growth process2014In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 211, no 2, p. 397-402Article in journal (Refereed)
    Abstract [en]

    Real time monitoring of atomic layer deposition by quartz crystal microbalance (QCM) was used to follow the growth of ZrO2 thin films on graphene. The films were grown from ZrCl4 and H2O on graphene prepared by chemical vapor deposition method on 100-nm thick nickel film or on Cu-foil and transferred onto QCM sensor. The deposition was performed at a substrate temperature of 190 degrees C. The growth of the dielectric film on graphene was significantly retarded compared to the process carried out on QCM without graphene. After the deposition of dielectric films, the basic structure of graphene was retained.

  • 167.
    Högberg, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tengdelius, Lina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Samuelsson, Mattias
    Impact Coatings AB, Linkoping, Sweden .
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    beta-Ta and alpha-Cr thin films deposited by high power impulse magnetron sputtering and direct current magnetron sputtering in hydrogen containing plasmas2014In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 439, p. 3-8Article in journal (Refereed)
    Abstract [en]

    Thin films of beta-Ta and alpha-Cr were deposited on Si(1 0 0) and 1000 angstrom SiO2/Si(1 0 0), by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (dcMS) in hydrogen-containing plasmas. The films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, scanning electron microscopy, elastic recoil detection analysis, and four-point probe measurements. The results showed that 001-oriented beta-Ta films containing up to similar to 8 at% hydrogen were obtained with HiPIMS, albeit with no chemical shift evident in XPS. The 110 oriented alpha-Cr films display a hydrogen content less than the detection limit of 1 at%, but H-2 favors the growth of high-purity films for both metals. The beta-Ta films deposited with dcMS are columnar, which seems independent of H-2 presence in the plasma, while the films grown by HIPIMS are more fine-grained. The latter type of microstructure was present for the alpha-Cr films and found to be independent on choice of technique or hydrogen in the plasma. The beta-Ta films show a resistivity of similar to 140-180 mu Omega cm, while alpha-Cr films exhibit values around 30 mu Omega cm; the lowest values obtained for films deposited by HiPIMS and with hydrogen in the plasma for both metals.

  • 168.
    Goyenola, Cecilia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 12, p. 6514-6521Article in journal (Refereed)
    Abstract [en]

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

  • 169.
    Israr Qadir, Muhammad
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Jamil Rana, Sadaf
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Cathodoluminescence characterization of ZnO nanorods synthesized by chemical solution and of its conversion to ellipsoidal morphology2014In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 29, no 20, p. 2425-2431Article in journal (Refereed)
    Abstract [en]

    A facile and reproducible low-temperature (80 degrees C) solution route has been introduced to synthesize ZnO ellipsoids on silicon substrate without any pretreatment of the substrate or organic/inorganic additives. Scanning electron microscopy, transmission electron microscopy, and x-ray diffraction spectroscopy are performed to analyze the structural evolution, the single crystalline nature, and growth orientation at different stages of the synthetic process. The sequential formation mechanisms of heterogeneous nucleation in primary and secondary crystal growth behaviors have been discussed in detail. The presented results reveal that the morphology of micro/nanostructures with desired features can be optimized. The optical properties of grown structures at different stages were investigated using cathodoluminescence (CL). The monochromatic CL images were recorded to examine the UV and visible band emission contributions from the different positions of the intermediate and final structures of the individual ZnO ellipsoid. Significant enhancement in the defect level emission intensity at the central position of the structure reveals that the quality of the material improves as the reaction time is extended.

  • 170.
    Palisaitis, Justinas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 3, p. 034302-Article in journal (Refereed)
    Abstract [en]

    The early stages of InGaN/GaN quantum wells growth for In reduced conditions have been investigated for varying thickness and composition of the wells. The structures were studied by monochromated STEM–VEELS spectrum imaging at high spatial resolution. It is found that beyond a critical well thickness and composition, quantum dots (>20 nm) are formed inside the well. These are buried by compositionally graded InGaN, which is formed as GaN is grown while residual In is incorporated into the growing structure. It is proposed that these dots may act as carrier localization centers inside the quantum wells.

  • 171.
    Khranovskyy, Volodymyr
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, Martin O.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Radnóczi, György Zoltán
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Khalid, Abbas
    University of Dublin Trinity Coll, Ireland.
    Zhang, Hongzhou
    University of Dublin Trinity Coll, Ireland.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Correction: Photoluminescence study of basal plane stacking faults in ZnO nanowires (vol 4639, pg 50, 2014)2014In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 454, p. 279-279Article in journal (Other academic)
    Abstract [en]

    n/a

  • 172.
    Furlan, Andrej
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Uppsala University, Sweden .
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Crystallization characteristics and chemical bonding properties of nickel carbide thin film nanocomposites2014In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 26, no 41, p. 415501-415512Article in journal (Refereed)
    Abstract [en]

    The crystal structure and chemical bonding of magnetron-sputtering deposited nickel carbide Ni1−xCx (0.05≤x≤0.62) thin films have been investigated by high-resolution x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and soft x-ray absorption spectroscopy. By using x-ray as well as electron diffraction, we found carbon-containing hcp-Ni (hcp-NiCy phase), instead of the expected rhombohedral-Ni3C. At low carbon content (4.9 at%), the thin film consists of hcp-NiCy nanocrystallites mixed with a smaller amount of fcc-NiCx. The average grain size is about10–20 nm. With the increase of carbon content to 16.3 at%, the film contains single-phase hcp-NiCy nanocrystallites with expanded lattice parameters. With a further increase of carbon content to 38 at%, and 62 at%, the films transform to x-ray amorphous materials with hcp-NiCy and fcc-NiCx nanodomain structures in an amorphous carbon-rich matrix. Raman spectra of carbon indicate dominant sp2 hybridization, consistent with photoelectron spectra that show a decreasing amount of C–Ni phase with increasing carbon content. The Ni 3d–C 2p hybridization in the hexagonal structure gives rise to the salient double-peak structure in Ni 2p soft x-ray absorption spectra at 16.3 at% that changes with carbon content. We also show thatthe resistivity is not only governed by the amount of carbon, but increases by more than a factor of two when the samples transform from crystalline to amorphous.

  • 173.
    Abbasi, Mazhar Ali
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain, Mushtaque
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Decoration of ZnO nanorods with coral reefs like NiO nanostructures by the hydrothermal growth method and their luminescence study2014In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 7, no 1, p. 430-440Article in journal (Refereed)
    Abstract [en]

    Composite nanostructures of coral reefs like p-type NiO on n-type ZnO nanorods have been decorate on fluorine-doped tin oxide glass substrates by the hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy,  high-resolution transmission electron microscopy and X-ray diffraction techniques. This investigation has shown that the adopted synthesis has led to high crystalline quality nanostructures. Morphological study shows that the coral reefs like nanostructures are densely packed on the ZnO nanorods. Cathodoluminescence (CL) spectra for the synthesized composite nanostructures were dominated by a near band gap emission at 380 nm and by a broad interstitial defect related luminescence centered at ~630 nm. Spatially resolved CL images reveal that the luminescence originates mainly from the ZnO nanorods.

  • 174.
    Junesand, Carl
    et al.
    KTH Royal Institute Technology, Sweden .
    Gau, Ming-Horn
    KTH Royal Institute Technology, Sweden National Sun Yat Sen University, Taiwan .
    Sun, Yan-Ting
    KTH Royal Institute Technology, Sweden .
    Lourdudoss, Sebastian
    KTH Royal Institute Technology, Sweden .
    Lo, Ikai
    National Sun Yat Sen University, Taiwan .
    Jimenez, Juan
    University of Valladolid, Spain .
    Aitor Postigo, Pablo
    Institute Microelect Madrid, Spain .
    M. Morales, Fransisco
    University of Cadiz, Spain .
    Hernandez, Jesus
    University of Cadiz, Spain .
    Molina, Sergio
    University of Cadiz, Spain .
    Abdessamad, Aouni
    Fac Science and Technical Tanger, Morocco .
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pirouz, Pirouz
    Case Western Reserve University, OH 44106 USA .
    Defect reduction in heteroepitaxial InP on Si by epitaxial lateral overgrowth2014In: MATERIALS EXPRESS, ISSN 2158-5849, Vol. 4, no 1, p. 41-53Article in journal (Refereed)
    Abstract [en]

    Epitaxial lateral overgrowth of InP has been grown by hydride vapor phase epitaxy on Si substrates with a thin seed layer of InP masked with SiO2. Openings in the form of multiple parallel lines as well as mesh patterns from which growth occurred were etched in the SiO2 mask and the effect of different growth conditions in terms of V/III ratio and growth temperature on defects such as threading dislocations and stacking faults in the grown layers was investigated. The samples were characterized by cathodoluminescence and by transmission electron microscopy. The results show that the cause for threading dislocations present in the overgrown layers is the formation of new dislocations, attributed to coalescence of merging growth fronts, possibly accompanied by the propagation of pre-existing dislocations through the mask openings. Stacking faults were also pre-existing in the seed layer and propagated to some extent, but the most important reason for stacking faults in the overgrown layers was concluded to be formation of new faults early during growth. The formation mechanism could not be unambiguously determined, but of several mechanisms considered, incorrect deposition due to distorted bonds along overgrowth island edges was found to be in best agreement with observations.

  • 175.
    Tengdelius, Lina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Samuelsson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Direct current magnetron sputtered ZrB2 thin films on 4H-SiC(0001) and Si(100)2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 550, p. 285-290Article in journal (Refereed)
    Abstract [en]

    ZrB2 thin films have been synthesized using direct current magnetron sputtering from a ZrB2 compound target onto 4H-SiC(0001) and Si(100) substrates kept at different temperatures (no heating, 400 °C, and 550 °C), and substrate bias voltage (-20 V to -80 V). Time-of-flight energy elastic recoil detection analysis shows that all the films are near stoichiometric and have a low degree of contaminants, with O being the most abundant (< 1 at.%). The films are crystalline, and their crystallographic orientation changes from 0001 to a more random orientation with increased deposition temperature. X-ray diffraction pole figures and selected area electron diffraction patterns of the films deposited without heating reveal a fiber-texture growth. Four point probe measurements show typical resistivity values of the films ranging from ~95 to 200 μΩcm, decreasing with increased growth temperature and substrate bias.

  • 176.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Editorial Material: SPECIAL ISSUE CELEBRATING VOLUME 1002014In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 100, no SI, p. 1-1Article in journal (Other academic)
    Abstract [en]

    n/a

  • 177.
    Stueber, Michael
    et al.
    Karlsruhe Institute Technology, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Matthews, Allan
    University of Sheffield, England.
    Editorial Material: Special Issue of Surface and Coatings Technology on 25 Years of TiAlN Hard Coatings in Research and Industry Preface in SURFACE and COATINGS TECHNOLOGY, vol 257, issue , pp2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 257Article in journal (Other academic)
    Abstract [en]

    n/a

  • 178.
    Tholander, Christopher
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Effect of Al substitution on Ti, Al, and N adatom dynamics on TiN(001), (011), and (111) surfaces2014In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 630, p. 28-40Article in journal (Refereed)
    Abstract [en]

    Substituting Al for Ti in TiN(001), TiN(011), and N- and Ti-terminated TiN(111) surfaces has significant effects on adatom surface energetics which vary strongly with the adatom species and surface orientation. Here, we investigate Ti, Al, and N adatom surface dynamics using density functional methods. We calculate adatom binding and diffusion energies with both a nudged elastic band and grid-probing techniques. The adatom diffusivities are analyzed within a transition-state theory approximation. We determine the stable and metastable Ti, Al, and N binding sites on all three surfaces as well as the lowest energy migration paths. In general, adatom mobilities are fastest on TiN(001), slower on TiN(111), and slowest on TiN(011). The introduction of Al has two major effects on the surface diffusivity of Ti and Al adatoms. First, Ti adatom diffusivity on TiN(001) is significantly reduced near substituted Al surface atoms; we observe a 200% increase in Ti adatom diffusion barriers out of fourfold hollow sites adjacent to Al surface atoms, while Al adatom diffusivity between bulk sites is largely unaffected. Secondly, on TiN(111), the effect is opposite; Al adatoms are slowed near the substituted Al surface atom, while Ti adatom diffusivity is largely unaffected. In addition, we note the importance of magnetic spin polarization on Ti adatom binding energies and diffusion path. These results are of relevance for the atomistic understanding of Ti1-xAlxN alloy and Ti1-xAlxN/TiN multilayer thin-film growth processes.

  • 179.
    Kindlund, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Effect of WN content on toughness enhancement in V1–xWxN/MgO(001) thin films2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 3, p. 030603-Article in journal (Refereed)
    Abstract [en]

    The authors report the growth and mechanical properties of epitaxial B1 NaCl-structure V1-xWxN/MgO(001) thin films with 0 ≤ x ≤ 0.60. The Gibbs free energy of mixing, calculated using density functional theory (DFT), reveals that cubic V1-xWxN solid solutions with 0 ≤ x ≤ 0.7 are stable against spinodal decomposition and separation into the equilibrium cubic-VN and hexagonal-WN binary phases. The authors show experimentally that alloying VN with WN leads to a monotonic increase in relaxed lattice parameters, enhanced nanoindentation hardnesses, and reduced elastic moduli. Calculated V1-xWxN lattice parameters and elastic moduli  (obtained from calculated C11, C12, and C44 elastic constants) are in good agreement with experimental results. The observed increase in alloy hardness, with a corresponding decrease in the elastic modulus at higher x values, combined with DFT-calculated decreases in shear to bulk moduli ratios, and increased Cauchy pressures (C12–C44) with increasing x reveal a trend toward increased toughness.

  • 180.
    Xia, Chao
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Johansson, Leif I
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Zakharov, A A
    MAX-lab, Lund University, Lund, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Effects of Al on epitaxial graphene grown on 6H-SiC(0001)2014In: Materials Research Express, ISSN 2053-1591, Vol. 1, no 1, p. 1-13, article id 015606Article in journal (Refereed)
    Abstract [en]

    Aluminum was deposited on epitaxial monolayer-grown graphene on SiC(0001). The effects of annealing up to 1200 °C on the surface and interface morphology, chemical composition, and electron band structure were analyzed in situ by synchrotron-based techniques at the MAX Laboratory. After heating at around 400 °C, Al islands or droplets are observed on the surface and the collected Si 2p, Al 2p, and C 1s core levels spectra indicate Al intercalation at the graphene SiC interface. Also, the original single π -band splits into two, indicating decoupling of the carbon buffer layer and the formation of a quasi-free-standing bilayer-like electronic structure. Further heating at higher temperatures from 700 to 900 °C yields additional chemical reactions. Broader core level spectra are then observed and clear changes in the π -bands near the Dirac point are detected. More electron doping was detected at this stage since one of the π -bands has shifted to about 1.1 eV below the Fermi level. Different ordered phases of (7x7), (4x4), (1x1)Al , and (1x1)G were also observed on the surface in this temperature range. The original single π π-band was restored after heating at ~1200°C, although an Al signal was still able to be detected.

  • 181.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sangiovanni, Davide G.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Effects of atomic ordering on the elastic properties of TiN- and VN-based ternary alloys2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, no Part 1, p. 145-153Article in journal (Refereed)
    Abstract [en]

    Improved toughness is one of the central goals in the development of wear-resistant coatings. Previous studies of toughness in transition metal nitride alloys have addressed the effects of chemical composition in these compounds. Herein, we use density functional theory to study the effects of various metal sublattice configurations, ranging from fully ordered to fully disordered, on the mechanical properties of VM2N and TiM2N (M2 = W, Mo) ternary alloys. Results show that all alloys display high incompressibility, indicating strong M-N bonds. Disordered atomic arrangements yield lower values of bulk moduli and C11 elastic constants, as well as higher values of C44 elastic constants, compared to ordered structures. We attribute the low C44 values of ordered structures to the formation of fully-bonding states perpendicular to the applied stress. We find that the ductility of these compounds is primarily an effect of the increased valence electron concentration induced upon alloying.

  • 182.
    Mei, A.B.
    et al.
    University of Illinois, IL 61801 USA University of Illinois, IL 61801 USA .
    Wilson, R.B.
    University of Illinois, IL 61801 USA University of Illinois, IL 61801 USA .
    Li, D.
    University of Illinois, IL 61801 USA University of Illinois, IL 61801 USA .
    Cahill, David G.
    University of Illinois, IL 61801 USA University of Illinois, IL 61801 USA .
    Rockett, A.
    University of Illinois, IL 61801 USA University of Illinois, IL 61801 USA .
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Elastic constants, Poisson ratios, and the elastic anisotropy of VN(001), (011), and (111) epitaxial layers grown by reactive magnetron sputter deposition2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 21, p. 214908-Article in journal (Refereed)
    Abstract [en]

    Elastic constants are determined for single-crystal stoichiometric NaCl-structure VN(001), VN(011), and VN(111) epitaxial layers grown by magnetically unbalanced reactive magnetron sputter deposition on 001-, 011-, and 111-oriented MgO substrates at 430 degrees C. The relaxed lattice parameter a(o) = 0.4134 +/- 0.0004 nm, obtained from high-resolution reciprocal space maps, and the mass density rho = 6.1 g/cm(3), determined from the combination of Rutherford backscattering spectroscopy and film thickness measurements, of the VN layers are both in good agreement with reported values for bulk crystals. Sub-picosecond ultrasonic optical pump/probe techniques are used to generate and detect VN longitudinal sound waves with measured velocities v(001) = 9.8 +/- 0.3, v(011) = 9.1 +/- 0.3, and v(111) = 9.1 +/- 0.3 km/s. The VN c(11) elastic constant is determined from the sound wave velocity measurements as 585 +/- 30 GPa; the c(44) elastic constant, 126 +/- 3 GPa, is obtained from surface acoustic wave measurements. From the combination of c(11), c(44), v(hkl), and rho we obtain the VN c(12) elastic constant 178 +/- 33 GPa, the VN elastic anisotropy A = 0.62, the isotropic Poisson ratio nu = 0.29, and the anisotropic Poisson ratios nu(001) = 0.23, nu(011) = 0.30, and nu(111) = 0.29.

  • 183.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Frodelius, Jenny
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnfält, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Epitaxial growth of gamma-Al2O3 on Ti2AlC(0001) by reactive high-power impulse magnetron sputtering2014In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 4, no 1, p. 017138-Article in journal (Refereed)
    Abstract [en]

    Al2O3 was deposited by reactive high-power impulse magnetron sputtering at 600 degrees C onto pre-deposited Ti2AlC(0001) thin films on alpha-Al2O3(0001) substrates. The Al2O3 was deposited to a thickness of 65 nm and formed an adherent layer of epitaxial gamma-Al2O3(111) as shown by transmission electron microscopy. The demonstration of epitaxial growth of gamma-Al2O3 on Ti2AlC (0001) open prospects for growth of crystalline alumina as protective coatings on Ti2AlC and related nanolaminated materials. The crystallographic orientation relationships are gamma-Al2O3(111)//Ti2AlC(0001) (out-of-plane) and gamma-Al2O3(2 (2) over bar0)//Ti2AlC(11 (2) over bar0) (in-plane) as determined by electron diffraction. Annealing in vacuum at 900 degrees C resulted in partial decomposition of the Ti2AlC by depletion of Al and diffusion into and through the gamma-Al2O3 layer.

  • 184.
    Tucker, Mark
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Czigany, Zsolt
    Research Institute for Technical Physics and Materials Science, RCNS, Budapest, Hungary.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Näslund, Lars-Åke
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 14, p. 144312-Article in journal (Refereed)
    Abstract [en]

    Carbon and carbon nitride films (CNx , 0 ≤ x ≤ 0.26) were deposited by filtered pulsed cathodic arc and were investigated using transmission electron microscopy and X-ray photoelectron spectroscopy. A “fullerene-like” (FL) structure of ordered graphitic planes, similar to that of magnetron sputtered FL-CNx films, was observed in films deposited at 175 °C and above, with N2 pressures of 0 and 0.5 mTorr. Higher substrate temperatures and significant nitrogen incorporation are required to produce similar FL structure by sputtering, which may, at least in part, be explained by the high ion charge states and ion energies characteristic of arc deposition. A gradual transition from majority sp3-hybridized films to sp2 films was observed with increasing substrate temperature. High elastic recovery, an attractive characteristic mechanical property of FL-CNx films, is evident in arc-deposited films both with and without nitrogen content, and both with and without FL structure.

  • 185.
    Ektarawong, Annop
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    First-principles study of configurational disorder in B4C using a superatom-special quasirandom structure method2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 2, article id 024204Article in journal (Refereed)
    Abstract [en]

    Configurationally disordered crystalline boron carbide, with the composition B4C, is studied using first-principles calculations. We investigate both dilute and high concentrations of carbon-boron substitutional defects. For the latter purpose, we suggest a superatoms picture of the complex structure and combine it with a special quasirandom structure approach for disorder. In this way, we model a random distribution of high concentrations of the identified low-energy defects: (1) bipolar defects and (2) rotation of icosahedral carbon among the three polar-up sites. Additionally, the substitutional disorder of the icosahedral carbon at all six polar sites, as previously discussed in the literature, is also considered. Two configurational phase transitions from the ordered to the disordered configurations are predicted to take place upon an increase in temperature using a mean-field approximation for the entropy. The first transition, at 870 K, induces substitutional disorder of the icosahedral carbon atoms among the three polar-up sites; meanwhile the second transition, at 2325 K, reveals the random substitution of the icosahedral carbon atoms at all six polar sites coexisting with bipolar defects. Already the first transition removes the monoclinic distortion existing in the ordered ground-state configuration and restore the rhombohedral system (R3m). The restoration of inversion symmetry yielding the full rhombohedral symmetry (R (3) over barm) on average, corresponding to what is reported in the literature, is achieved after the second transition. Investigating the effects of high pressure on the configurational stability of the disordered B4C phases reveals a tendency to stabilize the ordered ground-state configuration as the configurationally ordering/disordering transition temperature increases with pressure exerted on B4C. The electronic density of states, obtained from the disordered phases, indicates a sensitivity of the band gap to the degree of configurational disorder in B4C.

  • 186.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Growth and properties of amorphous Ti-B-Si-N thin films deposited by hybrid HIPIMS/DC-magnetron co-sputtering from TiB2 and Si targets2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 259, p. 442-447Article in journal (Refereed)
    Abstract [en]

    Amorphous nitrides are explored for their homogenous structure and potential use as wear-resistant coatings, beyond their much studied nano-and microcrystalline counterparts. (TiB2)1−xSixNy thin films were deposited on Si(001) substrates by a hybrid technique of high power impulse magnetron sputtering (HIPIMS) combined with dc magnetron sputtering (DCMS) using TiB2 and Si targets in a N2/Ar atmosphere. By varying the sputtering dc power to the Si target from 200 to 2000 W while keeping the average power to the TiB2-target, operated in HIPIMS mode, constant at 4000 W, the Si content in the films increased gradually from x=0.01 to x=0.43. The influence of the Si content on the microstructure, phase constituents, and mechanical properties were systematically investigated. The results show that the microstructure of as-deposited (TiB2)1−xSixNy films changes from nanocrystalline with 2-4 nm TiN grains for x=0.01 to fully electron diffraction amorphous for x=0.22. With increasing Si content, the hardness of the films increases from 8.5 GPa with x=0.01 to 17.2 GPa with x=0.43.

  • 187.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Howe, B.M.
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, Ohio, USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mei, A. R. B.
    Frederick Seitz Materials Research Laboratory and Materials Science Department, University of Illinois, USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, J.E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hf-Al-Si-N multilayers deposited by reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target using high-flux, low-energy modulated substrate bias: film growth and properties2014Manuscript (preprint) (Other academic)
    Abstract [en]

    Hf1−x−yAlxSiyN (0≤x≤0.14, 0≤y≤0.13) single layers and multilayer films are grown on Si(001) at a substrate temperature Ts=250 °C using ultrahigh vacuum magnetically-unbalanced reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target in a 5%-N2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1−x−yAlxSiyN is controlled during growth by varying the ion energy (Ei) of the ions incident at the film surface, keeping the ion-to-metal flux ratio (Ji/JMe) constant at 8. By sequentially switching Ei between 10 and 40 eV, Hf0.77Al0.10Si0.13N/Hf0.78Al0.14Si0.08N multilayers with bilayer periods Λ = 2-20 nm are grown, in which the Si2p bonding state changes from predominantly Si-Si bonds for films grown at Ei = 10 eV, to mainly Si-N bonds at Ei = 40 eV. Multilayer hardness values increase monotonically from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm, while multilayer fracture toughness increases with increasing Λ. Multilayers with Λ = 10 nm have the optimized property combination of being bothrelatively hard, H∼24 GPa, and fracture tough.

  • 188.
    Metaferia, Wondwosen
    et al.
    KTH, Sweden .
    Dev, Apurba
    KTH, Sweden .
    Kataria, Himanshu
    KTH, Sweden .
    Junesand, Carl
    KTH, Sweden .
    Sun, Yan-Ting
    KTH, Sweden .
    Anand, Srinivasan
    KTH, Sweden .
    Tommila, Juha
    Tampere University of Technology, Finland .
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Guina, Mircea
    Tampere University of Technology, Finland .
    Niemi, Tapio
    Tampere University of Technology, Finland .
    Lourdudoss, Sebastian
    KTH, Sweden .
    High quality InP nanopyramidal frusta on Si2014In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, no 21, p. 4624-4632Article in journal (Refereed)
    Abstract [en]

    Nanosized octagonal pyramidal frusta of indium phosphide were selectively grown at circular hole openings on a silicon dioxide mask deposited on indium phosphide and indium phosphide pre-coated silicon substrates. The eight facets of the frusta were determined to be {111} and {110} truncated by a top (100) facet. The size of the top flat surface can be controlled by the diameter of the openings in the mask and the separation between them. The limited height of the frusta is attributed to kinetically controlled selective growth on the (100) top surface. Independent analyses with photoluminescence, cathodoluminescence and scanning spreading resistance measurements confirm certain doping enrichment in the frustum facets. This is understood to be due to crystallographic orientation dependent dopant incorporation. The blue shift from the respective spectra is the result of this enrichment exhibiting the Burstein-Moss effect. Very bright panchromatic cathodoluminescence images indicate that the top surfaces of the frusta are free from dislocations. The good optical and morphological quality of the nanopyramidal frusta indicates that the fabrication method is very attractive for the growth of site-, shape-, and number-controlled semiconductor quantum dot structures on silicon for nanophotonic applications.

  • 189.
    Kukli, Kaupo
    et al.
    University of Helsinki, Finland University of Tartu, Estonia .
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Link, Joosep
    NICPB, Estonia .
    Kemell, Marianna
    University of Helsinki, Finland .
    Puukilainen, Esa
    University of Helsinki, Finland .
    Heikkila, Mikko
    University of Helsinki, Finland .
    Hoxha, Roland
    University of Tartu, Estonia .
    Tamm, Aile
    University of Tartu, Estonia .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stern, Raivo
    NICPB, Estonia .
    Ritala, Mikko
    University of Helsinki, Finland .
    Leskela, Markku
    University of Helsinki, Finland .
    Holmium and titanium oxide nanolaminates by atomic layer deposition2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 565, p. 165-171Article in journal (Refereed)
    Abstract [en]

    Nanolaminate (nanomultilayer) thin films of TiO2 and Ho2O3 were grown on Si(001) substrates by atomic layer deposition at 300 degrees C from alkoxide and beta-diketonate based metal precursors and ozone. Individual layer thicknesses were 2 nm for TiO2 and 4.5 nm for Ho2O3. As-deposited films were smooth and X-ray amorphous. After annealing at 800 degrees C and higher temperatures the nanolaminate structure was destroyed by solid-state reaction to form Ho2Ti2O7. The films demonstrated diamagnetic or paramagnetic behaviour in the as-deposited state. After annealing, the films possessed net magnetic moment, allowing one to record saturation magnetization and weak coercivity.

  • 190.
    Birch, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Buffet, J.-C.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Clergeau, J.-F.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Correa, J.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    van Esch, P.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Ferraton, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Guerard, B.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Halbwachs, J.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Hall-Wilton, R.
    European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Khaplanov, A.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France; European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Koza, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Piscitelli, F.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Zbiri, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    In-beam test of the Boron-10 Multi-Grid neutron detector at the IN6 time-of-flight spectrometer at the ILL2014In: INTERNATIONAL WORKSHOP ON NEUTRON OPTICS AND DETECTORS (NOPandD 2013), IOP Publishing: Conference Series / Institute of Physics (IoP) , 2014, Vol. 528, no 012040Conference paper (Refereed)
    Abstract [en]

    A neutron detector concept based on solid layers of boron carbide enriched in 1 B has been in development for the last few years as an alternative for He-3 by collaboration between the ILL, ESS and Linkoping University. This Multi-Grid detector uses layers of aluminum substrates coated with (B4C)-B-10 on both sides that are traversed by the incoming neutrons. Detection is achieved using a gas counter readout principle. By segmenting the substrate and using multiple anode wires, the detector is made inherently position sensitive. This development is aimed primarily at neutron scattering instruments with large detector areas, such as time-of-flight chopper spectrometers. The most recent prototype has been built to be interchangeable with the He-3 detectors of IN6 at ILL. The 1 B detector has an active area of 32 x 48 cm(2). It was installed at the IN6 instrument and operated for several weeks, collecting data in parallel with the regularly scheduled experiments, thus providing the first side-by-side comparison with the conventional He-3 detectors. Results include an efficiency comparison, assessment of the in-detector scattering contribution, sensitivity to gamma-rays and the signal-to-noise ratio in time-of-flight spectra. The good expected performance has been confirmed with the exception of an unexpected background count rate. This has been identified as natural alpha activity in aluminum. New convertor substrates are under study to eliminate this source of background.

  • 191.
    Tengstrand, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nedfors, N.
    Uppsala University, Sweden.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, U.
    Uppsala University, Sweden.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Impact Coatings AB, SE-58216 Linkoping, Sweden.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Incorporation effects of Si in TiCx thin films2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 392-397Article in journal (Refereed)
    Abstract [en]

    Ti-Si-C thin films with varying Si content between 0 to 10 at.% were deposited by DC magnetron sputtering from elemental targets. The effects on microstructure and lattice parameters were investigated using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and first-principles calculations. The results show that the growth of pure TiCx onto Al2O3(0001) substrates at a temperature of 350 degrees C yields (111) epitaxial and understoichiometric films with x similar to 0.7. For Si contents up to 4 at.%, the TiCx epitaxy is retained locally. Si starts to segregate out from the TiCx to column boundaries at concentrations between 1 and 4 at.%, and causes a transition from epitaxial to polycrystalline growth above 4 at.%. Eventually, the top part of the films form a nanocomposite of crystalline TiC grains surrounded by amorphous SiC and C for Si contents studied up to 10 at.%. The results show that Si takes the place of carbon when incorporated in the TiC lattice.

  • 192.
    Eriksson, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mráz, S.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Schneider, J. M.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Influence of Ar and N2 Pressure on Plasma Chemistry, Ion Energy, and Thin Film Composition during Filtered Arc Deposition from Ti3SiC2 Cathodes2014In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 42, no 11, p. 3498-3507Article in journal (Refereed)
    Abstract [en]

    Arc plasma from Ti3SiC2 compound cathodes used in a filtered dc arc system has been characterized with respect to plasma chemistry and charge-state resolved ion energies. In vacuum, the plasma composition is dominated by Ti ions, with concentrations of 84.3, 9.3, and 6.4 at% for Ti, Si, and C ions, respectively. The reduced amount of Si and most notably C compared with the cathode composition is confirmed by analysis of film composition in corresponding growth experiments. The deposition of light-element deficient films is thus related to plasma generation or filter transport. The ion energy distributions in vacuum range up to 140, 90, and 70 eV for Ti, Si, and C, respectively. Corresponding average ion energies of 48, 36, and 27 eV are reduced upon introduction of gas, down to around 5 eV at 0.6 Pa Ar or 0.3 Pa N2 for all species. In vacuum, the charge state distributions of Si and C are shifted to higher values compared with corresponding elemental cathodes, likely caused by changed effective electron temperature of the plasma stemming from compound cathode material and/or by electron impact ionization in the filter. The average ion charge states are reduced upon addition of Ar, ranging between 1.97 and 1.48 for Ti, 1.91 and 1.46 for Si, and 1.25 and 1.02 for C. Similar effects are observed upon introduction of N2, though with more efficient charge state reduction with pressure. It is conceivable that the pressure-induced changes in ion energy and charge state are crucial for the film synthesis from a microstructure evolution point of view, as they affect the ion-surface interactions through supply of energy, especially when substrate biasing is employed during arc deposition from a compound cathode.

  • 193.
    Tengdelius, Lina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnetron sputtering of epitaxial ZrB2 thin films on 4H-SiC(0001) and Si(111)2014In: Physica Status Solidi (a), ISSN 1862-6319, Vol. 211, no 3, p. 636-640Article in journal (Refereed)
    Abstract [en]

    Epitaxial ZrB2 thin films were deposited at a temperature of 900 °C on 4H-SiC(0001) and Si(111) substrates by magnetron sputtering from a ZrB2 source at high rate ~80 nm/min. The films were analyzed by thin film X-ray diffraction including pole figure measurements and reciprocal space mapping as well as high resolution electron microscopy.

  • 194.
    Kindlund, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Martínez-de-Olcoz, L.
    Grupo de Capas Finas e Ingeniería de Superficies, Facultad de Física. Universidad de Barcelona. Dep. Física Aplicada y Óptica, Barcelona, Spain.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Microstructure and mechanical properties of: V0.5Mo0.5Nx(111)/Al2O3(0001) thin films2014Manuscript (preprint) (Other academic)
    Abstract [en]

    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.

  • 195.
    Tengstrand, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nedfors, Nils
    Department of Chemistry, The Ångström Laboratory, Uppsala University.
    Andersson, Matilda
    Department of Chemistry, The Ångström Laboratory, Uppsala University.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Department of Chemistry, The Ångström Laboratory, Uppsala University.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Model for electron-beam-induced crystallization of amorphous Me-Si-C (Me = Nb or Zr) thin films2014In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 29, no 23, p. 2854-2862Article in journal (Refereed)
    Abstract [en]

    We use transmission electron microscopy (TEM) for in-situ studies of electronbeam-induced crystallization behavior in thin films of amorphous transition metal silicon carbides based on Zr (group 4 element) and Nb (group 5). Higher silicon content stabilized the amorphous structure while no effects of carbon were detected. Films with Nb start to crystallize at lower electron doses than Zr-containing ones. During the crystallization equiaxed MeC grains are formed in all samples with larger grains for Zr (~5nm) compared to Nb (~2nm). Eventually the sample stabilizes and the crystallization process stops. A model is presented where the metal carbide grains nucleate and grow while Si segregates into the remaining amorphous matrix. At a certain Si concentration in the matrix the graingrowth stops.

  • 196.
    Nedfors, Nils
    et al.
    Uppsala University, Sweden .
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Uppsala University, Sweden .
    Nb-B-C thin films for electrical contact applications deposited by magnetron sputtering2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 4, p. 041503-Article in journal (Refereed)
    Abstract [en]

    The high wear resistance, high chemical inertness, and high electrical conductivity of magnetron-sputtered transition metal diborides make them a candidate material for sliding electrical contacts. However, their high hardness makes it difficult to penetrate surface oxides, resulting in a high electrical contact resistance. In this study, the authors have investigated how the contact resistance can be improved by the formation of softer Nb-B-C films. The Nb-B-C films were deposited by magnetron sputtering and shown to exhibit a nanocomposite microstructure consisting of nanocrystalline NbB2-x grains with a solid solution of C separated by an amorphous BCx phase. The formation of the BCx phase reduces the hardness from 41 GPa for the NbB2-x film to 19 GPa at 36 at. % C. As a consequence the contact resistance is drastically reduced and the lowest contact resistance of 35 m Omega (contact force 5N) is achieved for a film containing 30 at. % C. However, crack formation and subsequent delamination and fragmentation is observed for the C-containing Nb-B-C films in tribology tests resulting in high friction values for these films.

  • 197.
    Naguib, M.
    et al.
    Drexel University, PA 19104 USA.
    Bentzel, G. W.
    Drexel University, PA 19104 USA.
    Shah, J.
    Drexel University, PA 19104 USA.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA.
    Caspi, E. N.
    Nucl Research Centre Negev, Israel.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, M. W.
    Drexel University, PA 19104 USA.
    New Solid Solution MAX Phases: (Ti-0.5, V-0.5)(3)AlC2, (Nb-0.5, V0.5)(2)AlC, (Nb-0.5, V-0.5)(4)AlC3 and (Nb-0.8, Zr-0.2)(2)AlC2014In: MATERIALS RESEARCH LETTERS, ISSN 2166-3831, Vol. 2, no 4, p. 233-240Article in journal (Refereed)
    Abstract [en]

    We synthesized the following previously unreported aluminum-containing solid solution M(n+1)AX(n) phases: (Ti-0.5, V-0.5)(3)AlC2, (Nb-0.5, V-0.5)(2)AlC, (Nb-0.5, V-0.5)(4)AlC3 and (Nb-0.8, Zr-0.2)(2)AlC. Rietveld analysis of powder X-ray diffraction patterns was used to calculate the lattice parameters and phase fractions. Heating Ti, V, Al and C elemental powders-in the molar ratio of 1.5: 1.5: 1.3: 2-to 1, 450 degrees C for 2 h in flowing argon, resulted in a predominantly phase pure sample of (Ti-0.5, V-0.5)(3)AlC2. The other compositions were not as phase pure and further work on optimizing the processing parameters needs to be carried out if phase purity is desired.

  • 198.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Arts and Sciences.
    Bolz, Stephan
    CemeCon AG, Wűrselen, Germany.
    Koelker, Werner
    CemeCon AG, Wűrselen, Germany.
    Schiffers, Christoph
    CemeCon AG, Wűrselen, Germany.
    Lemmer, Oliver
    CemeCon AG, Wűrselen, Germany.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA .
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Novel strategy for low-temperature, high-rate growth of dense, hard, and stress-free refractory ceramic thin films2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 4, p. 041515-Article in journal (Refereed)
    Abstract [en]

    Growth of fully dense refractory thin films by means of physical vapor deposition (PVD) requires elevated temperatures T-s to ensure sufficient adatom mobilities. Films grown with no external heating are underdense, as demonstrated by the open voids visible in cross-sectional transmission electron microscopy images and by x-ray reflectivity results; thus, the layers exhibit low nanoindentation hardness and elastic modulus values. Ion bombardment of the growing film surface is often used to enhance densification; however, the required ion energies typically extract a steep price in the form of residual rare-gas-ion-induced compressive stress. Here, the authors propose a PVD strategy for the growth of dense, hard, and stress-free refractory thin films at low temperatures; that is, with no external heating. The authors use TiN as a model ceramic materials system and employ hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS and DCMS) in Ar/N-2 mixtures to grow dilute Ti1-xTaxN alloys on Si(001) substrates. The Ta target driven by HIPIMS serves as a pulsed source of energetic Ta+/Ta2+ metal-ions, characterized by in-situ mass and energy spectroscopy, while the Ti target operates in DCMS mode (Ta-HIPIMS/Ti-DCMS) providing a continuous flux of metal atoms to sustain a high deposition rate. Substrate bias V-s is applied in synchronous with the Ta-ion portion of each HIPIMS pulse in order to provide film densification by heavy-ion irradiation (m(Ta) = 180.95 amu versus m(Ti) = 47.88 amu) while minimizing Ar+ bombardment and subsequent trapping in interstitial sites. Since Ta is a film constituent, primarily residing on cation sublattice sites, film stress remains low. Dense Ti0.92Ta0.08N alloy films, 1.8 mu m thick, grown with T-s less than= 120 degrees C (due to plasma heating) and synchronized bias, V-s = 160 V, exhibit nanoindentation hardness H = 25.9 GPa and elastic modulus E = 497 GPa compared to 13.8 and 318 GPa for underdense Ti-HIPIMS/Ti-DCMS TiN reference layers (T-s less than 120 degrees C) grown with the same V-s, and 7.8 and 248 GPa for DCMS TiN films grown with no applied bias (T-s less than 120 degrees C). Ti0.92Ta0.08N residual stress is low, sigma = -0.7 GPa, and essentially equal to that of Ti-HIPIMS/Ti-DCMS TiN films grown with the same substrate bias.

  • 199.
    Jones, N.G.
    et al.
    Department Mat Science and Met, England .
    Humphrey, C.
    Department Mat Science and Met, England .
    Connor, L.D.
    Diamond Light Source, England .
    Wilhelmsson, O.
    Sandvik Heating Technology AB, Sweden .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stone, H.J.
    Department Mat Science and Met, England .
    Giuliani, F.
    University of London Imperial Coll Science Technology and Med, England .
    Clegg, W.J.
    Department Mat Science and Met, England .
    On the relevance of kinking to reversible hysteresis in MAX phases2014In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 69, p. 149-161Article in journal (Refereed)
    Abstract [en]

    This paper examines the idea that reversible hysteresis in MAX phases is caused by the formation, growth and collapse of unstable, or incipient, kink bands. In situ X-ray diffraction of polycrystalline Ti3SiC2 in compression showed that residual elastic lattice strains developed during the first loading cycle and remained approximately constant afterwards. These residual strains were compressive in grains with a low Schmid factor and tensile in grains with a high Schmid factor, consistent with previous observations of plastically deformed hexagonal metals. In contrast, incipient kink bands would be expected to collapse completely, without any residual strain. Elastoplastic self-consistent simulations showed that reversible hysteresis is predicted if some grains yield by slip on the basal plane, while others remain predominantly elastic, giving both the experimentally observed magnitude of the work dissipated and its dependence on the maximum applied stress. The reversible hysteresis in single crystals was studied by cyclically indenting thin films of Ti3SiC2 and Ti3SiC2/TiC multilayers on Al2O3 substrates. The work dissipated in the multilayer films was greater than in Ti3SiC2 alone, despite the reduction in volume fraction of Ti3SiC2. Reversible hysteresis was also observed during indentation of single-crystal cubic MgO, demonstrating that this behaviour can occur if there are insufficient slip systems to accommodate the strain around the indentation. These results show that reversible hysteresis is associated with conventional dislocation flow, without the need for unstable kinking.

  • 200.
    Khromov, Sergey
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 22, p. 223503-Article in journal (Refereed)
    Abstract [en]

    Freestanding bulk C-doped GaN wafers grown by halide vapor phase epitaxy are studied by optical spectroscopy and electron microscopy. Significant changes of the near band gap (NBG) emission as well as an enhancement of yellow luminescence have been found with increasing C doping from 5 × 1016 cm−3 to 6 × 1017 cm−3. Cathodoluminescence mapping reveals hexagonal domain structures (pits) with high oxygen concentrations formed during the growth. NBG emission within the pits even at high C concentration is dominated by a rather broad line at ∼3.47 eV typical for n-type GaN. In the area without pits, quenching of the donor bound exciton (DBE) spectrum at moderate C doping levels of 1–2 × 1017 cm−3 is observed along with the appearance of two acceptor bound exciton lines typical for Mg-doped GaN. The DBE ionization due to local electric fields in compensated GaN may explain the transformation of the NBG emission.

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