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  • 1.
    Alami, Jones
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating 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.
    Andersson, Jon M.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Lattemann, Martina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Wallin, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Böhlmark, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating 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.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering2007In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 7-8, p. 3434-3438Article in journal (Refereed)
    Abstract [en]

    Ta thin films were grown on Si substrates at different inclination angles with respect to the sputter source using high power impulse magnetron sputtering (HIPIMS), an ionized physical vapor deposition technique. The ionization allowed for better control of the energy and directionality of the sputtered species, and consequently for improved properties of the deposited films. Depositions were made on Si substrates with the native oxide intact. The structure of the as deposited films was investigated using X-ray diffraction, while a four-point probe setup was used to measure the resistivity. A substrate bias process-window for growth of bcc-Ta was observed. However, the process-window position changed with changing inclination angles of the substrate. The formation of this low-resistivity bcc-phase could be understood in light of the high ion flux from the HIPIMS discharge.

  • 2.
    Alami, Jones
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating 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.
    Emmerlich, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wilhelmsson, O.
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Jansson, U.
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Högberg, Hans
    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.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 4, p. 1731-1736Article in journal (Refereed)
    Abstract [en]

    We have deposited Ti-Si-C thin films using high-power impulse magnetron sputtering (HIPIMS) from a Ti3SiC2 compound target. The as-deposited films were composite materials with TiC as the main crystalline constituent. X-ray diffraction and photoelectron spectroscopy indicated that they also contained amorphous SiC, and for films deposited on inclined substrates, crystalline Ti5Si3Cx. The film morphology was dense and flat, while films deposited with dc magnetron sputtering under comparable conditions were rough and porous. Due to the high degree of ionization of the sputtered species obtained in HIPIMS, it is possible to control the film composition, in particular the C content, by tuning the substrate inclination angle, the Ar process pressure, and the bias voltage.

  • 3.
    Ali, Sharafat
    et al.
    Linnaeus University, Sweden; Corning Inc, NY 14831 USA.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Jonson, Bo
    Linnaeus University, Sweden.
    Eklund, Per
    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.
    Synthesis and characterization of the mechanical and optical properties of Ca-Si-O-N thin films deposited by RF magnetron sputtering2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 315, p. 88-94Article in journal (Refereed)
    Abstract [en]

    Ca-Si-O-N thin films were deposited on commercial soda-lime silicate float glass, silica wafers and sapphire substrates by RF magnetron co-sputtering from Ca and Si targets in an Ar/N-2/O-2 gas mixture. Chemical composition, surface morphology, hardness, reduced elastic modulus and optical properties of the films were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, nanoindentation, and spectroscopic ellipsometry. It was found that the composition of the films can be controlled by the Ca target power, predominantly, and by the reactive gas flow. Thin films in the Ca-Si-O-N system are composed of N and Ca contents up to 31 eq. % and 60 eq. %, respectively. The films thickness ranges from 600 to 3000 nm and increases with increasing Ca target power. The films surface roughness varied between 2 and 12 nm, and approximately decreases with increasing power of Ca target. The hardness (4-12 GPa) and reduced elastic modulus (65-145 GPa) of the films increase and decrease with the N and Ca contents respectively. The refractive index (1.56-1.82) is primarily dictated by the N content. The properties are compared with findings for bulk glasses in the Ca-Si-(Al)-O-N systems, and it is concluded that Ca-Si-O-N thin films have higher values of hardness, elastic modulus and refractive index than bulk glasses of similar composition. (C) 2017 Elsevier B.V. All rights reserved.

    The full text will be freely available from 2019-02-13 13:58
  • 4.
    Ali, Sharafat
    et al.
    Linnaeus University, Sweden.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . 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.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Jonson, Bo
    Linnaeus University, Sweden.
    Eklund, Per
    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.
    Novel transparent Mg-Si-O-N thin films with high hardness and refractive index2016In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 131Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for glass materials with better mechanical and optical properties for display and electronic applications. This paper describes the deposition of novel thin films of Mg-circle divide-Si-O-N onto float glass substrates. Amorphous thin films in the Mg-Si-O-N system with high nitrogen and magnesium contents were deposited by reactive RF magnetron co-sputtering from Mg and Si targets in Ar/N-2/O-2 gas mixtures. The thin films studied span an unprecedented range of compositions up to 45 at% Mg and 80 at% N out of cations and anions respectively. Thin films in the Mg-Si-O-N system were found to be homogeneous and transparent in the visible region. Mechanical properties like hardness (H) and reduced elastic modulus (Er) show high values, up to 21 GPa and 166 GPa respectively. The refractive index (1.87-2.00) increases with increasing magnesium and nitrogen contents. (C) 2016 Elsevier Ltd. All rights reserved.

  • 5.
    Alling, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Khatibi, Ali
    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.
    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.
    Theoretical investigation of cubic B1-like and corundum (Cr1−xAlx)2O3 solid solutionsManuscript (preprint) (Other academic)
    Abstract [en]

    First-principles calculations are employed to investigate the stability and properties of cubic rock-salt like (Cr1−xAlx)2O3 solid solutions, stabilized by metal site vacancies as recently reported experimentally. It is demonstrated that the metal site vacancies can indeed be ordered in a way that gives rise to a favorable coordination of all O atoms in the lattice. B1-like structures with ordered and disordered metal site vacancies are studied for (Cr0.5Al0.5)2O3 and found to a have cubic lattice spacing close to the values reported experimentally, in contrast to fluorite-like and perovskite structures. The obtained B1-like structures are higher in energy than corundum solid solutions for all compositions, but with an energy offset per atom similar to other metastable systems possible to synthesize with physical vapor deposition techniques. The obtained electronic structures show that the B1-like systems are semiconducting although with smaller band gaps than the corundum structure.

  • 6.
    Alling, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Khatibi, Ali
    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.
    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.
    Theoretical investigation of cubic B1-like and corundum (Cr1−xAlx)2O3 solid solutions2013In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 31, no 3Article in journal (Refereed)
    Abstract [en]

    First-principles calculations are employed to investigate the stability and properties of cubic rock-salt-like (Cr1−xAlx)2O3 solid solutions, stabilized by metal site vacancies as recently reported experimentally. It is demonstrated that the metal site vacancies can indeed be ordered in a way that gives rise to a suitable fourfold coordination of all O atoms in the lattice. B1-like structures with ordered and disordered metal site vacancies are studied for (Cr0.5Al0.5)2O3 and found to have a cubic lattice spacing close to the values reported experimentally, in contrast to fluorite-like and perovskite structures. The obtained B1-like structures are higher in energy than corundum solid solutions for all compositions, but with an energy offset per atom similar to other metastable systems possible to synthesize with physical vapor deposition techniques. The obtained electronic structures show that the B1-like systems are semiconducting although with smaller band gaps than the corundum structure.

  • 7.
    Anasori, Babak
    et al.
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Dahlqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Halim, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA.
    Ju Moon, Eun
    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.
    Caspi, Elad N.
    Drexel University, PA 19104 USA; Nucl Research Centre Negev, Israel.
    May, Steven J.
    Drexel University, PA 19104 USA.
    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.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel W.
    Drexel University, PA 19104 USA.
    Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC32015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 9, p. 094304-Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases-Mo2TiAlC2 and Mo2Ti2AlC3-synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m) Ti:1.1Al:2C with 1.5 less than= m less than= 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 degrees C for 4 h under Ar flow. In general, for m greater than= 2 an ordered 312 phase, (Mo2Ti) AlC2, was the majority phase; for mless than 2, an ordered 413 phase (Mo2Ti2)AlC3, was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo2TiAlC1.7 and Mo2Ti1.9Al0.9C2.5, respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo2TiAlC2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-Ti-Mo for Mo2Ti2AlC3, with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the Mn+1Xn blocks. At 331 GPa and 367 GPa, respectively, the Youngs moduli of the ordered Mo2TiAlC2 and Mo2Ti2AlC3 are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10K for both phases showed metallic behavior. (C) 2015 AIP Publishing LLC.

  • 8.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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.
    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.
    Ghandi, R
    Royal Institute Technology, KTH.
    Domeij, M
    Royal Institute Technology, KTH.
    Zetterling, C M
    Royal Institute Technology, KTH.
    Behan, G
    Trinity College Dublin.
    Zhang, H
    Trinity College Dublin.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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 characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001)2012In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 343, no 1, p. 133-137Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3GeC2 thin films were deposited on 4 degrees off-cut 4H-SiC(0001) using magnetron sputtering from high purity Ti, C, and Ge targets. Scanning electron microscopy and helium ion microscopy show that the Ti3GeC2 films grow by lateral step-flow with {11 (2) over bar0} faceting on the SiC surface. Using elastic recoil detection analysis, atomic force microscopy, and X-Ray diffraction the films were found to be substoichiometric in Ge with the presence of small Ge particles at the surface of the film.

  • 9.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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.
    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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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.
    Step-flow growth of nanolaminate Ti3SiC2 epitaxial layers on 4H-SiC(0 0 0 1)2011In: SCRIPTA MATERIALIA, ISSN 1359-6462, Vol. 64, no 12, p. 1141-1144Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2(0 0 0 1) films were deposited on 4 degrees off-cut 4H-SiC(0 0 0 1) wafers using magnetron sputtering. A lateral step-flow growth mechanism of the Ti3SiC2 was discovered by X-ray diffraction, elastic recoil detection analysis, atomic force microscopy and electron microscopy. Helium ion microscopy revealed contrast variations on the Ti3SiC2 terraces, suggesting a mixed Si and Ti(C) termination. Si-rich growth conditions results in Ti3SiC2 layers with pronounced {1 1 (2) over bar 0) faceting and off-oriented TiSi2 crystallites, while stoichiometric growth yields truncated {1 (1) over bar 0 0) terrace edges.

  • 10.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ghandi, R
    Royal Institute of Technology.
    Domeij, M
    Royal Institute of Technology.
    Zetterling, C-M
    Royal Institute of Technology.
    Lu, Jun
    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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 4, p. 042108-Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linear transmission line measurements. Rapid thermal annealing at 950 degrees C for 1 min of as-deposited films yielded ohmic contacts to n-type SiC with contact resistances in the order of 10(-4) Omega cm(2). Transmission electron microscopy shows that the interface between Ti3SiC2 and n-type SiC is atomically sharp with evidence of interfacial ordering after annealing.

  • 11.
    Bugnet, M
    et al.
    University of Poitiers, France .
    Mauchamp, V
    University of Poitiers, France .
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jaouen, M
    University of Poitiers, France .
    Cabioch, T
    University of Poitiers, France .
    Contribution of core-loss fine structures to the characterization of ion irradiation damages in the nanolaminated ceramic Ti3AlC22013In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 61, no 19, p. 7348-7363Article in journal (Refereed)
    Abstract [en]

    The effect of low-energy ion irradiation on the nanolaminated Ti3AlC2 is investigated by means of X-ray diffraction, transmission electron microscopy, electron energy loss and X-ray absorption spectroscopy. The chemical sensitivity and local order probing from core-loss edges provide new insights into the structural modifications induced under irradiation. From the analysis of the C K energy loss near-edge structure and Al K X-ray absorption near-edge structure by ab initio calculations, the influence of the layered structure of this compound on the irradiation damage is demonstrated, and damage is found to be preferentially localized in the aluminum planes of the structure. On the basis of comparisons between calculations and experimental spectra, a structural model is proposed for the irradiated state. This study emphasizes the utility of core-loss fine structure analysis to enhance understanding of ion irradiation-induced damage in complex crystalline materials.

  • 12.
    Cabioch, Thierry
    et al.
    University of Poitiers, France.
    Alkazaz, Malaz
    University of Poitiers, France.
    Beaufort, Marie-France
    University of Poitiers, France.
    Nicolai, Julien
    University of Poitiers, France.
    Eyidi, Dominique
    University of Poitiers, France.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Poitiers, France.
    Ti2AlN thin films synthesized by annealing of (Ti plus Al)/AlN multilayers2016In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 80, p. 58-63Article in journal (Refereed)
    Abstract [en]

    Single-phase Ti2AlN thin films were obtained by annealing in vacuum of (Ti + Al)/AIN multilayers deposited at room temperature by magnetron sputtering onto single-crystalline (0001) 4H-SiC and (0001) Al2O3 substrates. In-situ X-ray diffraction experiments combined with ex-situ cross-sectional transmission electron microscopy observations reveal that interdiffusion processes occur in the multilayer at a temperature of similar to 400 degrees C leading to the formation of a (Ti, Al, N) solid solution, having the hexagonal structure of alpha-Ti, whereas the formation of Ti2AlN occurs at 550-600 degrees C. Highly oriented (0002) Ti2AlN thin films can be obtained after an annealing at 750 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.

  • 13.
    Cabioch, Thierry
    et al.
    University of Poitiers.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mauchamp, Vincent
    University of Poitiers.
    Jaouen, Michel
    University of Poitiers.
    Structural investigation of substoichiometry and solid solution effects in Ti2Al(C-x,N1-x)(y) compounds2012In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 32, no 8, p. 1803-1811Article in journal (Refereed)
    Abstract [en]

    The milling, cold compaction and thermal annealing (4 h-1400 degrees C-Ar flow) of Ti, TiC, Al and AlN powders were used to produce Ti2Al(CxN(1-x))(y) compounds with x = 0, 0.25, 0.5, 0.75, 1 and 0.7 andlt;= y andlt;= 1. X-ray diffraction analysis, scanning electron microscopy observations combined with microanalysis confirmed the formation of the almost pure Ti(2)A/CxN(1-x) carbonitrides for y=1 whereas increasing amounts of titanium aluminides were formed when y decreases. Proportions of the different phases deduced from Rietveld refinements of the X-ray diffractograms indicate that no or very poor substoichiometry in carbon was possible in carbide whereas C and N deficiency can be achieved in nitrides and carbonitrides Ti2AlCxN(1-x). Electron Energy Loss Spectroscopy investigations confirm that carbonitrides can have at least 20% of vacancies on the C or N site. The a lattice parameter varies linearly with x whereas it is not the case for the c lattice parameter, its values being lower for the carbonitrides. Furthermore, a strong broadening of the carbonitrides XRD peaks is observed, a phenomenon that can be mainly attributed to C and N concentration gradients inside the samples.

  • 14.
    Cabioch, Thierry
    et al.
    Université de Poitiers, France.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mauchamp, Vincent
    Université de Poitiers, France.
    Jaouen, Michel
    Université de Poitiers, France.
    Barsoum, Michel W.
    Université de Poitiers, France and Drexel University, Philadelphia, USA.
    Tailoring of the thermal expansion of Cr2(Alx,Ge1−x)C phases2013In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 33, no 4, p. 897-904Article in journal (Refereed)
    Abstract [en]

    We report thermal expansion coefficients of the end members and solid-solution compounds in the Cr2(Alx,Ge1−x)C system. All samples studied were essentially phase-pure Cr2AlxGe1−xC except the Cr2GeC sample, which contained a substantial fraction of Cr5Ge3Cx. X-ray diffraction performed in the 25–800 °C temperature range shows that the in-plane thermal expansion remains essentially constant at about 14 ± 1 × 10−6 K−1 irrespective of Al content. The thermal expansion of the c axis decreases monotonically from 17 ± 1 × 10−6 K−1 for Cr2GeC to ∼12 ± 1 × 10−6 K−1 with increasing Al content. At around the Cr2(Al0.75,Ge0.25)C composition, the thermal expansion coefficients along the two directions are equal; a useful property to minimize thermal residual stresses. This study thus demonstrates that a solid-solution approach is a route for tuning a physical property like the thermal expansion. For completeness, we also include a structure description of the Cr5Ge3Cx phase, which has been reported before but is not well documented. Its space group is P63/mcm and its a and c lattice parameters are 7.14 Å and 4.88 Å, respectively. We also measured the thermal expansion coefficients of the Cr5Ge3Cx phase. They are found to be 16.3 × 10−6 K−1 and 28.4 × 10−6 K−1 along the a and c axes, respectively. Thus, the thermal expansion coefficients of Cr5Ge3Cx are highly anisotropic and considerably larger than those of the Cr2(Alx,Ge1−x)C phases.

  • 15.
    Du, Yong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Shanghai Inst Technol, Peoples R China.
    Chen, Jiageng
    Shanghai Inst Technol, Peoples R China.
    Liu, Xin
    Shanghai Inst Technol, Peoples R China.
    Lu, Chun
    Shenyang Aerosp Univ, Peoples R China.
    Xu, Jiayue
    Shanghai Inst Technol, Peoples R China.
    Paul, Biplab
    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.
    Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing2018In: Coatings, ISSN 2079-6412, Vol. 8, no 1, article id 25Article in journal (Refereed)
    Abstract [en]

    Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K.

  • 16.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Multifunctional nanostructured Ti-Si-C thin films2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this Thesis, I have investigated multifunctional nanostructured Ti-Si-C thin films synthesized by magnetron sputtering in the substrate-temperature range from room temperature to 900 °C. The studies cover high-temperature growth of Ti3SiC2 and Ti4SiC3, low-temperature growth of Ti-Si-C nanocomposites, and Ti-Si-C-based multi¬layers, as well as their electrical, mechanical, and thermal-stability properties. Ti3SiC2 and Ti4SiC3 were synthesized homoepitaxially onto bulk Ti3SiC2 from individual sputtering targets and heteroepitaxially onto Al2O3(0001) substrates from a Ti3SiC2 target at substrate temperatures of 700 – 900 °C. In the latter case, the film composition exhibits excess C compared to the nominal target composition due to differences between species in angular and energy distribution and gas-phase scattering processes. Ti buffering is shown to compensate for this excess C. The electrical-resistivity values of Ti3SiC2 and Ti4SiC3 thin films were measured to 21-32 uOhmcm and ~50 uOhmcm, respectively. The good conductivity is because the presence of Si layers enhances the relative strength of the metallic Ti-Ti bonds. The higher density of Si layers in Ti3SiC2 than in Ti4SiC3 explains why Ti3SiC2 is the better conductor of the two. Ti3SiC2 thin films are shown to be thermally stable up to 1000 – 1100 °C. Annealing at higher temperature results in decomposition of Ti3SiC2 by Si out-diffusion to the surface with subsequent evaporation. Above 1200 °C, TiCx layers recrystallized. Nanocomposites comprising nanocrystalline (nc-)TiC in an amorphous (a-)SiC matrix phase were deposited at substrate temperatures in the range 100 – 300 °C. These nc-TiC/a-SiC films exhibit low contact resistance in electrical contacts and a ductile deformation behavior due to rotation and gliding of nc-TiC grains in the matrix. The ductile mechanical properties of nc-TiC/a-SiC are actually more similar to those of Ti3SiC2, which is very ductile due to kinking and delamination, than to those of the brittle TiC. Epitaxial TiC/SiC multilayers deposited at ~550 °C were shown to contain cubic SiC layers up to a thickness of ~2 nm. Thicker SiC layers gives a-SiC due to the corresponding increase in interfacial strain energy leading to loss of coherent-layer growth. Nanoindentation of epitaxial Ti3SiC2/TiC0.67 nanolaminates showed inhibition of kink-band formation in Ti3SiC2, as the lamination with the less ductile TiC effectively hindered this mechanism.

    List of papers
    1. Homoepitaxial growth of Ti-Si-C MAX-phase thin films on bulk Ti3SiC2 substrates
    Open this publication in new window or tab >>Homoepitaxial growth of Ti-Si-C MAX-phase thin films on bulk Ti3SiC2 substrates
    Show others...
    2007 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 304, no 1, p. 264-269Article in journal (Refereed) Published
    Abstract [en]

    Ti3SiC2 films were grown on polycrystalline Ti3SiC2 bulk substrates using DC magnetron sputtering. The crystallographic orientation of the film grains is shown to be determined by the respective substrate-grain orientation through homoepitaxial MAX-phase growth. For a film composition close to Ti:Si:C=3:1:2, the films predominantly consist of MAX phases, both Ti3SiC2 and the metastable Ti4SiC3. Lower Si content resulted in growth of TiC with Ti3SiC2 as a minority phase. Thus, MAX-phase heterostructures with preferred crystallographic relationships can also be realized.

    Keywords
    Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, Physical vapor deposition processes, Carbides, Nanomaterials
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14471 (URN)10.1016/j.jcrysgro.2007.02.014 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    2. Magnetron sputtering of Ti3SiC2 thin films from a Ti3SiC2 compound target
    Open this publication in new window or tab >>Magnetron sputtering of Ti3SiC2 thin films from a Ti3SiC2 compound target
    Show others...
    2007 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 25, no 5, p. 1381-1388Article in journal (Refereed) Published
    Abstract [en]

    Ti3 Si C2 thin films were synthesized by magnetron sputtering from Ti3 Si C2 and Ti targets. Sputtering from a Ti3 Si C2 target alone resulted in films with a C content of ∼50 at. % or more, due to gas-phase scattering processes and differences in angular and energy distributions between species ejected from the target. Addition of Ti to the deposition flux from a Ti3 Si C2 target is shown to bind the excess C in Ti Cx intergrown with Ti3 Si C2 and Ti4 Si C3. Additionally, a substoichiometric Ti Cx buffer layer is shown to serve as a C sink and enable the growth of Ti3 Si C2.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14472 (URN)10.1116/1.2757178 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    3. Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
    Open this publication in new window or tab >>Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
    Show others...
    2005 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, no 6, p. 2486-2495Article in journal (Refereed) Published
    Abstract [en]

    We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300  °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290  GPa, respectively. The electrical resistivity was 330  µ  cm for optimal Ar pressure (4  mTorr) and substrate temperature (300  °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6  µ at a contact force of 800  N compared to 3.2  µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.

    Keywords
    titanium compounds, silicon compounds, wide band gap semiconductors, nanocomposites, amorphous semiconductors, thin films, sputter deposition, electron microscopy, X-ray diffraction, X-ray photoelectron spectra, surface morphology, ductility, indentation, hardness, electrical resistivity, electrical contacts, contact resistance
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14473 (URN)10.1116/1.2131081 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    4. Microstructure and electrical properties of Ti-Si-C-Ag nanocomposite thin films
    Open this publication in new window or tab >>Microstructure and electrical properties of Ti-Si-C-Ag nanocomposite thin films
    Show others...
    2007 (English)In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 201, no 14, p. 6465-6469Article in journal (Refereed) Published
    Abstract [en]

    Ti–Si–C–Ag nanocomposite coatings consisting of nanocrystalline TiC in an amorphous Si matrix with segregated Ag were deposited by dual magnetron sputtering from Ti3SiC2 and Ag targets. As evidenced by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, for Ag contents below 10 at.%, the Ag forms 10 nm large crystallites that are homogeneously distributed in the films. For higher Ag contents, coalescence during growth results in the formation of >  100 nm Ag islands on the film surface. The electrical resistivity of the coatings was measured in a four-point-probe setup, and ranged from 340 μΩcm (for Ti–Si–C coatings without Ag) to 40 μΩcm (for high Ag content).

    Keywords
    Sputtering, Titanium carbide, Silver; Resistivity, X-ray diffraction, Electron microscopy
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14474 (URN)10.1016/j.surfcoat.2006.12.016 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2016-08-31
    5. High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
    Open this publication in new window or tab >>High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
    Show others...
    2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 4, p. 1731-1736Article in journal (Refereed) Published
    Abstract [en]

    We have deposited Ti-Si-C thin films using high-power impulse magnetron sputtering (HIPIMS) from a Ti3SiC2 compound target. The as-deposited films were composite materials with TiC as the main crystalline constituent. X-ray diffraction and photoelectron spectroscopy indicated that they also contained amorphous SiC, and for films deposited on inclined substrates, crystalline Ti5Si3Cx. The film morphology was dense and flat, while films deposited with dc magnetron sputtering under comparable conditions were rough and porous. Due to the high degree of ionization of the sputtered species obtained in HIPIMS, it is possible to control the film composition, in particular the C content, by tuning the substrate inclination angle, the Ar process pressure, and the bias voltage.

    Place, publisher, year, edition, pages
    Institutionen för fysik, kemi och biologi, 2006
    Keywords
    HIPIMS, Titanium silicon carbide
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-10437 (URN)10.1016/j.tsf.2006.06.015 (DOI)000242931900079 ()
    Note

    Original publication: J. Alami, P. Eklund, J. Emmerlich, O. Wilhelmsson, U. Jansson, H. Högberg, L. Hultman, & U. Helmersson, High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target, 2006, Thin Solid Films, (515), 4, 1731-1736. http://dx.doi.org/10.1016/j.tsf.2006.06.015. Copyright: Elsevier B.V., http://www.elsevier.com/.

    Available from: 2007-12-14 Created: 2007-12-14 Last updated: 2017-12-14Bibliographically approved
    6. Electrical resistivity of Tin+1ACn (A = Si, Ge, Sn, n = 1–3) thin films
    Open this publication in new window or tab >>Electrical resistivity of Tin+1ACn (A = Si, Ge, Sn, n = 1–3) thin films
    Show others...
    2007 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 22, no 8, p. 2279-2287Article in journal (Refereed) Published
    Abstract [en]

    We have investigated the electrical resistivity of (0001)-oriented Tin+1ACn (A = Si, Ge, Sn, n = 1–3) thin films deposited by magnetron sputtering onto Al2O3(0001) substrates at temperatures ranging from 500 to 950 °C. Four-point-probe measurements show that all films are good conductors with resistivity values of ∼21–51 μΩ cm for Ti–Si–C films, ∼15–50 μΩ cm for Ti–Ge–C films, and ∼46 μΩ cm for Ti2SnC. We find a general trend of decreasing resistivity with decreasing n for the Ti–Si–C and Ti–Ge–C systems due to the increased metallicity obtained with increasing density of A-element layers. We also show that crystalline quality and competitive growth of impurity phases affect the measured resistivity values. The effect of a given impurity phase largely depends on its location in the sample. Specifically, a TiCx layer in the center of the film constricts the current flow and results in an increased measured resistivity value. However, TiCx transition or seed layers at the substrate–film interface as well as surface segregation of Ge and Ti5Ge3Cx (for Ti–Ge–C) have only little effect on the measured resistivity values. For the Ti–Sn–C system, the resistivity is mainly influenced by the segregation of metallic Sn, yielding a wide spread in the measured values ranging from 20–46 μΩ cm, in the order of increased film purity.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14476 (URN)10.1557/jmr.2007.0284 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    7. Photoemission studies of Ti3SiC2 and nanocrystalline-TiC/amorphous-SiC nanocomposite thin films
    Open this publication in new window or tab >>Photoemission studies of Ti3SiC2 and nanocrystalline-TiC/amorphous-SiC nanocomposite thin films
    Show others...
    2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 4, p. 045417-Article in journal (Refereed) Published
    Abstract [en]

    Photoemissionstudies using synchrotron radiation have been performed on epitaxial Ti3SiC2(0001)and compound nanocrystalline (nc-)TiC/amorphous (a-)SiC thin films deposited by magnetronsputtering. As-introduced samples were found to be covered by surfaceoxides, SiOx and TiOx. These oxides could be removed byin-situ annealing to ~1000  °C. For as-annealed Ti3SiC2(0001), surface Si wasobserved and interpreted as originating from decomposition of Ti3SiC2 throughSi out-diffusion. For nc-TiC/a-SiC annealed in situ to ~1000  °C, thesurface instead exhibited a dominant contribution from graphitic carbon, alsowith the presence of Si, due to C and Siout-diffusion from the a-SiC compound or from grain boundaries.

    Keywords
    titanium compounds, silicon compounds, wide band gap semiconductors, nanocomposites, amorphous state, epitaxial layers, sputtered coatings, photoelectron spectra, surface composition, annealing, decomposition, surface diffusion, grain boundaries
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14477 (URN)10.1103/PhysRevB.74.045417 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    8. Thermal stability of Ti3SiC2 thin films
    Open this publication in new window or tab >>Thermal stability of Ti3SiC2 thin films
    Show others...
    2007 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 55, no 4, p. 1479-1488Article in journal (Refereed) Published
    Abstract [en]

    The thermal stability of Ti3SiC2(0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to ∼1000 °C for 25 h. Annealing at 1100–1200 °C results in the rapid decomposition of Ti3SiC2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti3C2 slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti3C2 slabs into (1 1 1)-oriented TiC0.67 layers, which begin recrystallizing at 1300 °C. Ab initio calculations are provided supporting the presented decomposition mechanisms.

    Keywords
    Ti3SiC2 thin films, Phase transformations, X-ray diffraction, Transmission electron microscopy, Ab initio electron theory
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14478 (URN)10.1016/j.actamat.2006.10.010 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    9. Epitaxial TiC/SiC multilayers
    Open this publication in new window or tab >>Epitaxial TiC/SiC multilayers
    2007 (English)In: Physica status solidi (RRL): rapid research letters, ISSN 1862-6254, Vol. 1, no 3, p. 113-115Article in journal (Refereed) Published
    Abstract [en]

    Epitaxial TiC/SiC multilayers were grown by magnetron sputtering at a substrate temperature of 550 °C, where SiC is normally amorphous. The epitaxial TiC template induced growth of cubic SiC up to a thickness of ~2 nm. Thicker SiC layers result in a direct transition to growth of the metastable amorphous SiC followed by renucleation of nanocrystalline TiC layers

    Keywords
    61.10.Nz, 68.37.Lp, 68.55.-a, 81.05.Je, 81.07.Bk, 81.15.Kk
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14479 (URN)10.1002/pssr.200701027 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2016-08-31
    10. Intrusion-type deformation in epitaxial Ti3SiC2/TiCx nanolaminates
    Open this publication in new window or tab >>Intrusion-type deformation in epitaxial Ti3SiC2/TiCx nanolaminates
    Show others...
    2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 12, p. 123124-Article in journal (Refereed) Published
    Abstract [en]

    We investigate the deformation of epitaxial Ti3 Si C2 (0001) Ti Cx (111) (x∼0.67) nanolaminates deposited by magnetron sputtering. Nanoindentation and transmission electron microscopy show that the Ti3 Si C2 layers deform via basal plane slip and intrusion into the TiC layers, suppressing kink-band and pile-up deformation behaviors analogous with monolithic Ti3 Si C2. This remarkable response to indentation is due to persistent slip in the TiC layers and prevention of gross slip throughout the nanolaminate by the interleaving Ti3 Si C2 layers. Hardness and Young's modulus were measured as ∼15 and ∼240 GPa, respectively.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14480 (URN)10.1063/1.2789710 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
  • 17.
    Eklund, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Novel ceramic Ti-Si-C nanocomposite coatings for electrical contact applications2007In: Surface Engineering, ISSN 0267-0844, E-ISSN 1743-2944, Vol. 23, no 6, p. 406-411Article in journal (Refereed)
    Abstract [en]

    Nanocomposite coatings consisting of TiC nanocrystallties embedded in an amorphous SiC matrix (nc-TiC/a-SiC) have been produced using magnetron sputtering from a Ti3SiC2 target onto electrical contact components at a temperature below 300°C. The as deposited nanocomposites were employed as electrical contact materials. Results show that when contacted against Ag, they exhibit somewhat higher contact resistance than Ag against Ag, while preventing welding and potentially minimising wear. This is due to an adequate resistivity coupled with beneficial mechanical properties. The design of the nanoscale materials produced coatings with a relatively high nanoindentation hardness of 20 GPa, but with a ductile deformation behaviour. The ductility is explained by rotation and gliding of nc-TiC grains in the matrix. Therefore, the nanocomposite material can minimise problems with wear and welding while retaining low contact resistance. Consequently, this type of novel coating with appropriate mechanical properties offers a solution to problems in many electrical applications. Moreover, the use of physically vapour deposited coatings is promoted in some previously relatively unexploited areas of electrical contact applications. © 2007 Institute of Materials, Minerals and Mining.

  • 18.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Thin film growth and characterization of Ti-(Si,Ge)-C compounds2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes growth by de magnetron sputtering of thin film Ti-Si-C and Ti-Ge-C materials, with an emphasis on the deposition conditions for nanocomposite and epitaxial growth at low and high temperature processing, respectively. In the Ti-Si-C materials system, I have synthesized nanocomposite thin films from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at low substrate temperature (300 oC and below). The films consisted ofnanocrystalline (nc-) TiC and amorphous (a-) SiC, with possible presence of a small amount of non-carbidic C. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 GPa and 290 GPa, respectively. The electrical resistivity was 330 μΩcm for optimal Ar pressure (4 mTorr) and substrate temperature (300 °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material, exhibiting contact resistances against Ag as low as 6μΩ at a contact force of 800 N compared to 3.2 μΩ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive gas test, with no N, Cl, or S contaminants entering the bulk of the films. Furthermore, the thesis describes epitaxial growth on Al2O3(0001) substrates of single- crystal thin films of the Mn+1AXn phases Ti2GeC and Ti3GeC2, and a new phase Ti4GeC3 as well as two new intergrown MAX structures, Ti5Ge2C3 and Ti7Ge2C5. X-ray diffraction shows that Ti-Ge-C MAX-phases require somewhat higher deposition temperatures (1000 oC) in a narrower window than their Ti-Si-C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young's modulus of 300 GPa, lower than that of Ti3SiC2, 320 GPa. Four point probe measurements yield resistivity values of 50-200 μΩcm. The lowest value is obtained for phase-pure Ti3GeC2(0001) films.

    List of papers
    1. Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
    Open this publication in new window or tab >>Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
    Show others...
    2005 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, no 6, p. 2486-2495Article in journal (Refereed) Published
    Abstract [en]

    We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300  °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290  GPa, respectively. The electrical resistivity was 330  µ  cm for optimal Ar pressure (4  mTorr) and substrate temperature (300  °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6  µ at a contact force of 800  N compared to 3.2  µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.

    Keywords
    titanium compounds, silicon compounds, wide band gap semiconductors, nanocomposites, amorphous semiconductors, thin films, sputter deposition, electron microscopy, X-ray diffraction, X-ray photoelectron spectra, surface morphology, ductility, indentation, hardness, electrical resistivity, electrical contacts, contact resistance
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14473 (URN)10.1116/1.2131081 (DOI)
    Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-13
    2. Epitaxial Ti2GeC, Ti3GeC2, and Ti4GeC3 MAX-phase thin films grown by magnetron sputtering
    Open this publication in new window or tab >>Epitaxial Ti2GeC, Ti3GeC2, and Ti4GeC3 MAX-phase thin films grown by magnetron sputtering
    Show others...
    2005 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 20, no 4, p. 779-782Article in journal (Refereed) Published
    Abstract [en]

    We have grown single-crystal thin films of Ti2GeC and Ti3GeC2 and a new phase Ti4GeC3, as well as two new intergrown MAX-structures, Ti5Ge2C3 and Ti7Ge2C5. Epitaxial films were grown on Al2O3(0001) substrates at 1000 °C using direct current magnetron sputtering. X-ray diffraction shows that Ti–Ge–C MAX-phases require higher deposition temperatures in a narrower window than their Ti–Si–C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young’s modulus of 300 GPa, lower than that of Ti3SiC2. Four-point probe measurements yield resistivity values of 50–200 μΩcm. The lowest value is obtained for phase-pure Ti3GeC2(0001) films.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-28436 (URN)10.1557/JMR.2005.0105 (DOI)13576 (Local ID)13576 (Archive number)13576 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
  • 19.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    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.
    Högberg, Hans
    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.
    Magnetron sputtering of Ti3SiC2 thin films from a Ti3SiC2 compound target2007In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 25, no 5, p. 1381-1388Article in journal (Refereed)
    Abstract [en]

    Ti3 Si C2 thin films were synthesized by magnetron sputtering from Ti3 Si C2 and Ti targets. Sputtering from a Ti3 Si C2 target alone resulted in films with a C content of ∼50 at. % or more, due to gas-phase scattering processes and differences in angular and energy distributions between species ejected from the target. Addition of Ti to the deposition flux from a Ti3 Si C2 target is shown to bind the excess C in Ti Cx intergrown with Ti3 Si C2 and Ti4 Si C3. Additionally, a substoichiometric Ti Cx buffer layer is shown to serve as a C sink and enable the growth of Ti3 Si C2.

  • 20.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Uppsala University.
    Högberg, Hans
    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.
    The M(n+1)AX(n) phases: Materials science and thin-film processing2010In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 8, p. 1851-1878Article, review/survey (Refereed)
    Abstract [en]

    This article is a Critical review of the M(n + 1)AX(n) phases ("MAX phases", where n = 1, 2, or 3) from a materials science perspective. MAX phases are a class of hexagonal-structure ternary carbides and nitrides ("X") of a transition metal ("M") and an A-group element. The most well known are Ti2AlC, Ti3SiC2, and Ti4AlN3. There are similar to 60 MAX phases with at least 9 discovered in the last five years alone. What makes the MAX phases fascinating and potentially useful is their remarkable combination of chemical, physical, electrical, and mechanical properties, which in many ways combine the characteristics of metals and ceramics. For example, MAX phases are typically resistant to oxidation and corrosion, elastically stiff, but at the same time they exhibit high thermal and electrical conductivities and are machinable. These properties stem from an inherently nanolaminated crystal structure, with M1 + nXn slabs intercalated with pure A-element layers. The research on MAX phases has been accelerated by the introduction of thin-film processing methods. Magnetron sputtering and arc deposition have been employed to synthesize single-crystal material by epitaxial growth, which enables studies of fundamental material properties. However, the surface-initiated decomposition of M(n + 1)AX(n) thin films into MX compounds at temperatures of 1000-1100 degrees C is much lower than the decomposition temperatures typically reported for the corresponding bulk material. We also review the prospects for low-temperature synthesis, which is essential for deposition of MAX phases onto technologically important substrates. While deposition of MAX phases from the archetypical Ti-Si-C and Ti-Al-N systems typically requires synthesis temperatures of similar to 800 degrees C, recent results have demonstrated that V2GeC and Cr2AlC can be deposited at similar to 450 degrees C. Also, thermal spray of Ti2AlC powder has been used to produce thick coatings. We further treat progress in the use of first-principle calculations for predicting hypothetical MAX phases and their properties. Together with advances in processing and materials analysis, this progress has led to recent discoveries of numerous new MAX phases such as Ti4SiC3, Ta4AlC3. and Ti3SnC2. Finally, important future research directions are discussed. These include charting the unknown regions in phase diagrams to discover new equilibrium and metastable phases, as well as research challenges in understanding their physical properties, such as the effects of anisotropy, impurities, and vacancies on the electrical properties, and unexplored properties such as Superconductivity, magnetism, and optics.

  • 21.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bugnet, Matthieu
    University of Poitiers.
    Mauchamp, Vincent
    University of Poitiers.
    Dubois, Sylvain
    University of Poitiers.
    Tromas, Christophe
    University of Poitiers.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Piraux, Luc
    Catholic University Louvain.
    Gence, Loiek
    Catholic University Louvain.
    Jaouen, Michel
    University of Poitiers.
    Cabioch, Thierry
    University of Poitiers.
    Epitaxial growth and electrical transport properties of Cr(2)GeC thin films2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 7, p. 075424-Article in journal (Refereed)
    Abstract [en]

    Cr(2)GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr(2)GeC was grown directly onto Al(2)O(3)(0001) at temperatures of 700-800 degrees C. These films have an epitaxial component with the well-known epitaxial relationship Cr(2)GeC(0001)//Al(2)O(3)(0001) and Cr(2)GeC(11andlt;(2) overbarandgt;0)//Al(2)O(3)(1andlt;(1)over barandgt;00) or Cr(2)GeC(11andlt;(2) over barandgt;0)//Al(2)O(3)(andlt;(1) over barandgt;2andlt;(1) over barandgt;0). There is also a large secondary grain population with (10andlt;(1)overbarandgt;3) orientation. Deposition onto Al(2)O(3)(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr(2)GeC(0001) with a virtually negligible (10andlt;(1) over barandgt;3) contribution. In contrast to the films deposited at 700-800 degrees C, the ones grown at 500-600 degrees C are polycrystalline Cr(2)GeC with (10andlt;(1) over barandgt;0)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 mu Omega cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

  • 22.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Dahlqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tengstrand, Olof
    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.
    Nedfors, Nils
    Uppsala University, Sweden .
    Jansson, Ulf
    Uppsala University, Sweden .
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Discovery of the Ternary Nanolaminated Compound Nb2GeC by a Systematic Theoretical-Experimental Approach2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 3, p. 035502-Article in journal (Refereed)
    Abstract [en]

    Since the advent of theoretical materials science some 60 years ago, there has been a drive to predict and design new materials in silicio. Mathematical optimization procedures to determine phase stability can be generally applicable to complex ternary or higher-order materials systems where the phase diagrams of the binary constituents are sufficiently known. Here, we employ a simplex-optimization procedure to predict new compounds in the ternary Nb-Ge-C system. Our theoretical results show that the hypothetical Nb2GeC is stable, and excludes all reasonably conceivable competing hypothetical phases. We verify the existence of the Nb2GeC phase by thin film synthesis using magnetron sputtering. This hexagonal nanolaminated phase has a and c lattice parameters of similar to 3.24 angstrom and 12.82 angstrom.

  • 23.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Emmerlich, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wilhelmsson, Ola
    Uppsala universitet.
    Jansson, Ulf
    Uppsala universitet.
    Isberg, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Synthesis and characterization of Ti-Si-C compounds for electrical contact applications2005In: IEEE Holm Conference on Electrical Contacts,2005, Piscataway: IEEE , 2005, p. 277-283Conference paper (Refereed)
  • 24.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Emmerlich, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Wilhelmsson, Ola
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
    Isberg, Peter
    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.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films2005In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, no 6, p. 2486-2495Article in journal (Refereed)
    Abstract [en]

    We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300  °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290  GPa, respectively. The electrical resistivity was 330  µ  cm for optimal Ar pressure (4  mTorr) and substrate temperature (300  °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6  µ at a contact force of 800  N compared to 3.2  µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.

  • 25.
    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.

  • 26.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Epitaxial TiC/SiC multilayers2007In: Physica status solidi (RRL): rapid research letters, ISSN 1862-6254, Vol. 1, no 3, p. 113-115Article in journal (Refereed)
    Abstract [en]

    Epitaxial TiC/SiC multilayers were grown by magnetron sputtering at a substrate temperature of 550 °C, where SiC is normally amorphous. The epitaxial TiC template induced growth of cubic SiC up to a thickness of ~2 nm. Thicker SiC layers result in a direct transition to growth of the metastable amorphous SiC followed by renucleation of nanocrystalline TiC layers

  • 27.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Joelsson, Torbjörn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ljungcrantz, Henrik
    Impact Coatings AB, Linköping, Sweden.
    Wilhelmsson, Ola
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Czigany, Zsolt
    Högberg, Hans
    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 electrical properties of Ti-Si-C-Ag nanocomposite thin films2007In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 201, no 14, p. 6465-6469Article in journal (Refereed)
    Abstract [en]

    Ti–Si–C–Ag nanocomposite coatings consisting of nanocrystalline TiC in an amorphous Si matrix with segregated Ag were deposited by dual magnetron sputtering from Ti3SiC2 and Ag targets. As evidenced by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, for Ag contents below 10 at.%, the Ag forms 10 nm large crystallites that are homogeneously distributed in the films. For higher Ag contents, coalescence during growth results in the formation of >  100 nm Ag islands on the film surface. The electrical resistivity of the coatings was measured in a four-point-probe setup, and ranged from 340 μΩcm (for Ti–Si–C coatings without Ag) to 40 μΩcm (for high Ag content).

  • 28.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kerdsongpanya, Sit
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Max Planck Institute Eisenforsch GmbH, Germany.
    Transition-metal-nitride-based thin films as novel energy harvesting materials2016In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 4, no 18, p. 3905-3914Article in journal (Refereed)
    Abstract [en]

    The last few years have seen a rise in the interest in early transition-metal and rare-earth nitrides, primarily based on ScN and CrN, for energy harvesting by thermoelectricity and piezoelectricity. This is because of a number of important advances, among those the discoveries of exceptionally high piezoelectric coupling coefficient in (Sc,Al)N alloys and of high thermoelectric power factors of ScN-based and CrN-based thin films. These materials also constitute well-defined model systems for investigating thermodynamics of mixing for alloying and nanostructural design for optimization of phase stability and band structure. These features have implications for and can be used for tailoring of thermoelectric and piezoelectric properties. In this highlight article, we review the ScN-and CrN-based transition-metal nitrides for thermoelectrics, and drawing parallels with piezoelectricity. We further discuss these materials as a models systems for general strategies for tailoring of thermoelectric properties by integrated theoretical-experimental approaches.

  • 29.
    Eklund, Per
    et al.
    University of Aarhus, Denmark.
    Mikkelsen, Niels-Jörgen
    CemeCon Scandinavia A/S, Åbyhøj, Denmark.
    Sillassen, Mikael
    University of Aarhus, Denmark.
    Bienk, Ewa
    CemeCon Scandinavia A/S, Åbyhøj, Denmark.
    Böttiger, Jörgen
    University of Aarhus, Denmark.
    Chromium oxide-based multilayer coatings deposited by reactive magnetron sputtering in an industrial setup2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 203, no 1, p. 156-159Article in journal (Refereed)
    Abstract [en]

    Chromium oxide-based multilayers were deposited by reactive magnetron sputtering in an industrial setup by employing one-fold substrate rotation and cyclic variation of the O2 flow. This simple method allows deposition of multilayers comprising alternating layers of ~ 1 μm thickness of columnar α-Cr2O3 and mixed layers consisting of ~ 50 nm-thick sublayers of amorphous CrOx and nanocrystalline Cr2O3.

  • 30.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Murugaiah, Anand
    Department of Materials Science and Engineering, Drexel University, Philadelphia, USA.
    Emmerlich, Jens
    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, Hungarian Academy of Sciences, Budapest, Hungary.
    Frodelius, Jenny
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Barsoum, Michel W.
    Department of Materials Science and Engineering, Drexel University, Philadelphia, USA.
    Högberg, Hans
    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.
    Homoepitaxial growth of Ti-Si-C MAX-phase thin films on bulk Ti3SiC2 substrates2007In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 304, no 1, p. 264-269Article in journal (Refereed)
    Abstract [en]

    Ti3SiC2 films were grown on polycrystalline Ti3SiC2 bulk substrates using DC magnetron sputtering. The crystallographic orientation of the film grains is shown to be determined by the respective substrate-grain orientation through homoepitaxial MAX-phase growth. For a film composition close to Ti:Si:C=3:1:2, the films predominantly consist of MAX phases, both Ti3SiC2 and the metastable Ti4SiC3. Lower Si content resulted in growth of TiC with Ti3SiC2 as a minority phase. Thus, MAX-phase heterostructures with preferred crystallographic relationships can also be realized.

  • 31.
    Eklund, Per
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Palmquist, Jens-Petter
    Kanthal AB.
    Höwing, Jonas
    Institute of Energy Technology, Kjeller, Norway.
    Trinh, David
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    El-Raghy, Tamer
    3-ONE-2, USA.
    Högberg, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Ta4AlC3: Phase determination, polymorphism and deformation2007In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 55, no 14, p. 4723-4729Article in journal (Refereed)
    Abstract [en]

    Ta4AlC3, a new member of the Mn+1AXn-phase family, has been synthesized and characterized (n = 1-3, M = early transition metal, A = A-group element, and X = C and/or N). Phase determination by Rietveld refinement of synchrotron X-ray diffraction data shows that Ta4AlC3 belongs to the P63/mmc space group with a and c lattice parameters of 3.10884 ± 0.00004 Å and 24.0776 ± 0.0004 Å, respectively. This is shown to be the α-polymorph of Ta4AlC3, with the same structure as Ti4AlN3. Lattice imaging by high-resolution transmission electron microscopy demonstrates the characteristic MAX-phase stacking of α-Ta4AlC3. Three modes of mechanical deformation of α-Ta4AlC3 are observed: lattice bending, kinking and delamination. © 2007.

  • 32.
    Eklund, Per
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Palmquist, Jens-Petter
    Uppsala universitet.
    Wilhelmsson, Ola
    Uppsala universitet.
    Jansson, Ulf
    Uppsala universitet.
    Emmerlich, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Högberg, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Comment on "Pulsed laser deposition and properties of Mn+1AXx phase formulated Ti3SiC2 thin films"2004In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 17, no 4, p. 977-978Article in journal (Other academic)
    Abstract [en]

    A recent paper by Hu et al. claimed synthesis of the MAX-phase Ti3SiC2at 100-300 °C using pulsed laser deposition. In this comment, we find that the evidence presented by Hu et al. is insufficient to show Ti3SiC2 formation. In fact, there is a simpler interpretation of their results from X-ray diffraction and transmission electron microscopy, namely that the material produced is a cubic TiC-based compound.

  • 33.
    Eklund, Per
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Palmquist, JP
    Department of Materials Chemistry, The Angström Laboratory, Uppsala University, Uppsala, Swede.
    Wilhelmsson, O
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Jansson, U
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Emmerlich, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Högberg, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Comment on "Pulsed laser deposition and properties of M(n+1)AX(x) phase formulated Ti3SiC2 thin films''2004In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 17, no 4, p. 977-978p. 977-978Article in journal (Other academic)
    Abstract [en]

    A recent paper by Hu et al. claimed synthesis of the MAX-phase Ti3SiC2 at 100 - 300 degreesC using pulsed laser deposition. In this comment, we find that the evidence presented by Hu et al. is insufficient to show Ti3SiC2 formation. In fact, there is a simpler interpretation of their results from X-ray diffraction and transmission electron microscopy, namely that the material produced is a cubic TiC-based compound.

  • 34.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    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.
    Layered ternary M(n+1)AX(n) phases and their 2D derivative MXene: an overview from a thin-film perspective2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 11, article id 113001Article, review/survey (Refereed)
    Abstract [en]

    Inherently and artificially layered materials are commonly investigated both for fundamental scientific purposes and for technological application. When a layered material is thinned or delaminated to its physical limits, a two-dimensional (2D) material is formed and exhibits novel properties compared to its bulk parent phase. The complex layered phases known as MAX phases (where M = early transition metal, A = A-group element, e.g. Al or Si, and X = C or N) are an exciting model system for materials design and the understanding of process-structure-property relationships. When the A layers are selectively etched from the MAX phases, a new type of 2D material is formed, named MXene to emphasize the relation to the MAX phases and the parallel with graphene. Since their discovery in 2011, MXenes have rapidly become established as a novel class of 2D materials with remarkable possibilities for composition variations and property tuning. This article gives a brief overview of MAX phases and MXene from a thin-film perspective, reviewing theory, characterization by electron microscopy, properties and how these are affected by the change in dimensionality, and outstanding challenges.

  • 35.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sridharan, M.
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-800 Aarhus C, Denmark.
    Singh, G.
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-800 Aarhus C, Denmark.
    Bottiger, Jorgen
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-800 Aarhus C, Denmark.
    Thermal Stability and Phase Transformations of γ-/Amorphous-Al2O3 Thin Films2009In: Plasma processes and polymers, ISSN 1612-8850, Vol. 6, no 1, p. 907-911Article in journal (Refereed)
    Abstract [en]

    Magnetron-sputtered Al2O3 thin films were annealed in ambient air. The phase compositions of the as-deposited Al2O3 films were (i) fully amorphous, (ii) nanocrystalline γ-Al2O3 in an amorphous Al2O3 matrix, and (iii) fully crystalline γ. For all samples, annealing to 1 100-1 150 °C resulted in a transformation to α-alumina. The transformation paths depend on the phase fraction of γ in the as-deposited films. For amorphous films and films with low initial γ fraction, the intermediate phase θ-Al2O3 appeared in the range of 1 000-1 100 °C. For predominantly crystalline γ-Al2O3 as-deposited films no intermediate Al2O3 phases were observed, indicating a direct γ-to-α phase transformation at ≈1 100 °C.

  • 36.
    Eklund, Per
    et al.
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
    Sridharan, Madanagurusamy
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
    Sillassen, Michael
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
    Böttiger, Jörgen
    Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
    α-Cr2O3 template-texture effect on α-Al2O3 thin-film growth2008In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 516, no 21, p. 7447-7450Article in journal (Refereed)
    Abstract [en]

    We employ textured α-Cr2O3 thin films as templates for growth of α-Al2O3 by reactive inductively coupled plasma magnetron sputtering. The texture of the template has a strong influence on the nucleation and growth of α-Al2O3. Extended growth of α-Al2O3 at a substrate temperature of 450 °C is obtained using a predominantly [101̄4]-textured α-Cr2O3 template layer, while only limited α-Al2O3 nucleation is seen on a [0001]-textured α-Cr2O3 template.

  • 37.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Emmerlich, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Johansson, Leif
    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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Photoemission studies of Ti3SiC2 and nanocrystalline-TiC/amorphous-SiC nanocomposite thin films2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 4, p. 045417-Article in journal (Refereed)
    Abstract [en]

    Photoemissionstudies using synchrotron radiation have been performed on epitaxial Ti3SiC2(0001)and compound nanocrystalline (nc-)TiC/amorphous (a-)SiC thin films deposited by magnetronsputtering. As-introduced samples were found to be covered by surfaceoxides, SiOx and TiOx. These oxides could be removed byin-situ annealing to ~1000  °C. For as-annealed Ti3SiC2(0001), surface Si wasobserved and interpreted as originating from decomposition of Ti3SiC2 throughSi out-diffusion. For nc-TiC/a-SiC annealed in situ to ~1000  °C, thesurface instead exhibited a dominant contribution from graphitic carbon, alsowith the presence of Si, due to C and Siout-diffusion from the a-SiC compound or from grain boundaries.

  • 38.
    Emmerlich, Jens
    et al.
    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.
    Rittrich, Dirk
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Electrical resistivity of Tin+1ACn (A = Si, Ge, Sn, n = 1–3) thin films2007In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 22, no 8, p. 2279-2287Article in journal (Refereed)
    Abstract [en]

    We have investigated the electrical resistivity of (0001)-oriented Tin+1ACn (A = Si, Ge, Sn, n = 1–3) thin films deposited by magnetron sputtering onto Al2O3(0001) substrates at temperatures ranging from 500 to 950 °C. Four-point-probe measurements show that all films are good conductors with resistivity values of ∼21–51 μΩ cm for Ti–Si–C films, ∼15–50 μΩ cm for Ti–Ge–C films, and ∼46 μΩ cm for Ti2SnC. We find a general trend of decreasing resistivity with decreasing n for the Ti–Si–C and Ti–Ge–C systems due to the increased metallicity obtained with increasing density of A-element layers. We also show that crystalline quality and competitive growth of impurity phases affect the measured resistivity values. The effect of a given impurity phase largely depends on its location in the sample. Specifically, a TiCx layer in the center of the film constricts the current flow and results in an increased measured resistivity value. However, TiCx transition or seed layers at the substrate–film interface as well as surface segregation of Ge and Ti5Ge3Cx (for Ti–Ge–C) have only little effect on the measured resistivity values. For the Ti–Sn–C system, the resistivity is mainly influenced by the segregation of metallic Sn, yielding a wide spread in the measured values ranging from 20–46 μΩ cm, in the order of increased film purity.

  • 39.
    Emmerlich, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Gassner, Gert
    Department of Physical Metallurgy and Materials Testing, University of Leoben, Austria.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Micro and macroscale tribological behavior of epitaxial Ti3SiC2 thin films2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 11-12, p. 914-919Article in journal (Refereed)
    Abstract [en]

    Ti3SiC2(0 0 0 1) thin films prepared by magnetron sputtering were investigated for their response to tribomechanical strain induced during ball-on-disk experiments with 6 mm alumina balls and scratch tests with a 1 μm cono-spherical diamond tip. Normal loads of 100 μN to 0.24 N were applied resulting in a friction coefficient of 0.1 for the low loads. With higher applied normal loads, the friction coefficient increased up to 0.8. Analysis of the wear tracks using atomic force microscopy, scanning electron microscopy, and Raman spectroscopy revealed excessive debris resulting in third-body abrasion and fast wear. The formation of the debris can be explained by the generation of subsurface delamination cracks on basal planes. Subsequent kink formation obstructs the ball movement which results in the removal of the kinked film parts.

  • 40.
    Emmerlich, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Music, Denis
    Materials Chemistry, RWTH Aachen University, Germany.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wilhelmsson, Ola
    Department of Materials Chemistry, Uppsala University, Uppsala, Sweden.
    Jansson, Ulf
    Department of Materials Chemistry, Uppsala University, Uppsala, Sweden.
    Schneider, Jochen M.
    Materials Chemistry, RWTH Aachen University, Germany.
    Högberg, Hans
    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.
    Thermal stability of Ti3SiC2 thin films2007In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 55, no 4, p. 1479-1488Article in journal (Refereed)
    Abstract [en]

    The thermal stability of Ti3SiC2(0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to ∼1000 °C for 25 h. Annealing at 1100–1200 °C results in the rapid decomposition of Ti3SiC2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti3C2 slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti3C2 slabs into (1 1 1)-oriented TiC0.67 layers, which begin recrystallizing at 1300 °C. Ab initio calculations are provided supporting the presented decomposition mechanisms.

  • 41.
    Eriksson, Anders
    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.
    Tengstrand, Olof
    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.
    Eklund, Per
    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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nanocolumnar Epitaxial Ti1-xSixN (0 ≤ x ≤ 0.18) Thin Films Grown by Dual Reactive Magnetron Sputtering on MgO (001), (011), and (111) Substrates2012Manuscript (preprint) (Other academic)
    Abstract [en]

    Ti1-xSixNy thin films and multilayers have been grown on single-crystal TiN-templated MgO (001), (011), and (111) substrates kept at 550 °C. Elemental Ti and Si targets were used in UVH reactive dual magnetron sputtering in a mixed Ar/N2 discharge. Composition analysis by time-of-flight energy elastic recoil detection analysis show that the films are close to stoichiometric (0.95 ≤ y ≤ 1.00) with respect to TiN over the wide range of Si concentrations 0 ≤ x ≤ 0.22. High-resolution transmission electron microscopy (TEM) combined with scanning TEM and energy dispersive Xray analysis show that all films grow epitaxially for x ≤ 0.18 and that as much as every fifth Ti atom can be replaced by Si (~10 at.%) in Ti1-xSixN(001). For the (011) and (111)-oriented films, however, only 1-2 at.% Si substitutes for Ti. Instead, Si segregates to form crystalline-to-amorphous SiNz (z ≈ 1) tissue phases, which promote the formation of epitaxial TiN nanocolumns. The nanocolumns have preferred {110} interfaces and {200} top facets and grow several hundreds  of nm in length.

  • 42.
    Eriksson, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tengstrand, Olof
    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.
    Eklund, Per
    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.
    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.
    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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Si incorporation in Ti1-xSixN films grown on TiN(001) and (001)-faceted TiN(111) columns2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 257, p. 121-128Article in journal (Refereed)
    Abstract [en]

    Thin films consisting of TiN nanocrystallites encapsulated in a fully percolated SiNy tissue phase are archetypes for hard and superhard nanocomposites. Here, we investigate metastable SiNy solid solubility in TiN and probe the effects of surface segregation during the growth of TiSiN films onto substrates that are either flat TiN(001)/MgO(001) epitaxial buffer layers or TiN(001) facets of length 1-5 nm terminating epitaxial TiN(111) nanocolumns, separated by voids, deposited on epitaxial TiN(111)/MgO(111) buffer layers. Using reactive magnetron sputter deposition, the TiSiN layers were grown at 550 degrees C and the TiN buffer layers at 900 degrees C On TiN(001), the films are NaCl-structure single-phase metastable Ti1-xSixN(001) with N/(Ti + Si) = 1 and 0 less than= x less than= 0.19. These alloys remain single-crystalline to critical thicknesses h(c) ranging from 100 +/- 30 nm with x = 0.13 to 40 +/- 10 nm with x = 0.19. At thicknesses h greater than h(c), the epitaxial growth front breaks down locally to form V-shaped polycrystalline columns with an underdense feather-like nanostructure. In contrast, the voided epitaxial TiN(111) columnar surfaces, as well as the TiN(001) facets, act as sinks for SiNy. For Ti1-xSixN layers with global average composition values less than x greater than = 0.16, the local x value in the middle of Ti1-xSixN columns increases from 0.08 for columns with radius r similar or equal to 2 nm to x = 0.14 with r similar or equal to 4 nm. The average out-of-plane lattice parameter of epitaxial nanocolumns encapsulated in SiNy decreases monotonically with increasing Si fraction less than x greater than, indicating the formation of metastable (Ti,Si)N solid solutions under growth conditions similar to those of superhard nanocomposites for which the faceted surfaces of nanograins also provide sinks for SiNy.

  • 43.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. 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.
    Smedfors, K.
    School of Information and Communication Technology, KTH, Stockholm, Sweden.
    Zetterling, C. -M
    School of Information and Communication Technology, KTH, Stockholm, Sweden.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. 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.
    Single-step synthesis process of Ti3SiC2 ohmic contacts on 4H-SiC by sputter-deposition of Ti2015In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 99, p. 53-56Article in journal (Refereed)
    Abstract [en]

    We report a single-step procedure for growth of ohmic Ti3SiC2 on 4H-SiC by sputter-deposition of Ti at 960 °C, based on the Ti–SiC solid-state reaction during deposition. X-ray diffraction and electron microscopy show the growth of interfacial Ti3SiC2. The as-deposited contacts are ohmic, in contrast to multistep processes with deposition followed by rapid thermal annealing. This procedure also offers the possibility of direct synthesis of oxygen-barrier capping layers before exposure to air, potentially improving contact stability in high-temperature and high-power devices.

  • 44.
    Fashandi, Hossein
    et al.
    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.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    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.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. 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.
    Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC2017In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 16, no 8, p. 814-818Article in journal (Refereed)
    Abstract [en]

    The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti3AuC2 and Ti3Au2C2 phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti3SiC2 single-crystal thin films with simultaneous out-diffusion of Si. Ti3IrC2 is subsequently produced by a substitution reaction of Ir for Au in Ti3Au2C2. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 degrees C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.

  • 45.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Katsnelson, Mikhail I.
    Radboud University of Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands / Dept. of Theoretical Physics and Applied Mathematics, Ural Federal University, Russia.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. School of Information and Communication Technology, KTH, Stockholm, Sweden.
    Dirac points with giant spin-orbit splitting in the electronic structure of two-dimensional transition-metal carbides2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 15Article in journal (Refereed)
    Abstract [en]

    We investigated the structural and electrical properties of 2D MXene sheets by means of firstprinciples density functional theory (DFT) calculations. To describe the Kohn-Sham states, plane wave basis set and projector augmented wave method (PAW) were used as implemented in the Vienna ab initio Simulation Package (VASP). We applied PBE parameterization of the generalized gradient approximation of the exchange and correlation energy functional to account for many-body effects of the interacting electron system. Convergent sampling of the Brillouin-zone was achieved by a Γ-centered 15×15×1 grid. In order to model a single sheet of MXene we ensured at least 30 Å vacuum between the periodically repeated sheets. For the structural optimization 1×10−3 eV/Å force criteria was used. The relativistic spin-orbit coupling effects were also included in our simulations regarding band structure and density of states.

  • 46.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lai, Chung-Chuan
    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.
    Rosén, Johanna
    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.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. 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.
    Ti2Au2C and Ti3Au2C2 formed by solid state reaction of gold with Ti2AlC and Ti3AlC22017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 69, p. 9554-9557Article in journal (Refereed)
    Abstract [en]

    Incorporation of layers of noble metals in non-van der Waals layered materials may be used to form novel layered compounds. Recently, we demonstrated a high-temperature-induced exchange process of Au with Si in the layered phase Ti3SiC2, resulting in the formation of Ti3AuC2 and Ti3Au2C2. Here, we generalize this technique showing that Au/Ti2AlC and Au/Ti3AlC2 undergo an exchange reaction at 650 [degree]C to form Ti2Au2C and Ti3Au2C2 and determine their structures by electron microscopy, X-ray diffraction, and ab initio calculations. These results imply that noble-metal-containing layered phases should be possible to synthesize in many systems. The metal to be introduced should be inert to the transition-metal carbide layers, and exhibit negative heat of mixing with the initial A element in a liquid phase or two-phase liquid/solid region at the annealing temperature.

  • 47.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Soldemo, M.
    KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
    Weissenrieder, J.
    KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
    Götelid, M.
    KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
    Eriksson, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor 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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Monolayer iron oxide grown on porous platinum sensing layers of carbon monoxide sensors2015Manuscript (preprint) (Other academic)
    Abstract [en]

    Mono-layer iron oxide has been deposited through e-beam evaporation on a silica supported poly-crystalline platinum (Pt) model catalyst and its CO oxidation characteristics obtained from mass spectrometry measurements under various CO and O2 concentrations (ranging from 100 to 900 ppm and 3 to 7 %, respectively) as well as at different temperatures (ranging from 130 to 220 °C) and compared to the CO oxidation on corresponding non-coated Pt samples. Fabricating the model system as a Metal Oxide Semiconductor (MOS) structure from 4H-SiC with a top layer of SiO2 (as the support material) and a thin, discontinuous polycrystalline Pt film as the metal (the active catalyst material) also provided the possibility to investigate whether changes in catalyst surface conditions could be electronically monitored through the changes in capacitance they induce across the MOS structure.

    A low-temperature shift in the activity to CO oxidation for the iron oxide modified compared to bare Pt catalysts similar to what has previously been reported on single-crystalline Pt was found also for the near-realistic MOS model catalyst. This low-temperature shift was furthermore reflected in the electrical measurements, strongly indicating a correlation between the MOS capacitance and the CO oxidation characteristics, both in the case of iron oxide coated and non-coated Pt samples. By monitoring the MOS capacitance during more than 200 hours of continuous operation and analyzing the iron oxide coated samples by photo electron spectroscopy it could also be concluded that the iron oxide coated model catalyst seemingly retains its CO oxidation characteristics and chemical/compositional integrity over time. These findings might not only point to the applicability of iron oxide modified Pt in practical applications but may also open up new possibilities regarding the utilization of MOS model systems in studying and understanding as well as tailor CO oxidation (and other) catalysts and/or gas sensors for specific applications.

  • 48.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Soldemo, Markus
    KTH Royal Institute Technology, Sweden.
    Weissenrieder, Jonas
    KTH Royal Institute Technology, Sweden.
    Gothelid, Mats
    KTH Royal Institute Technology, Sweden.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. 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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Applicability of MOS structures in monitoring catalytic properties, as exemplified for monolayer-iron-oxide-coated porous platinum films2016In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 344, p. 583-590Article in journal (Refereed)
    Abstract [en]

    Metal Oxide Semiconductor (MOS) capacitor devices comprised of monolayer iron oxide-coated as well as non-coated polycrystalline Pt deposited on oxidized silicon carbide substrates have been fabricated and their usefulness as realistic model systems in catalyst studies development was evaluated. The CO oxidation characteristics of both iron oxide- and non-coated Pt catalysts were investigated using mass spectrometry, monitoring the carbon dioxide production rate for different combinations of carbon monoxide (CO) and oxygen concentrations at various temperatures. Additionally, the output capacitance of the MOS model catalysts was recorded for each individual CO oxidation activity. A low-temperature shift in CO oxidation characteristics for the monolayer-coated compared to the non-coated Pt catalysts was observed, similar to that previously reported for monolayer iron oxide grown on single-crystalline Pt substrates. A strong correlation between the output capacitance of the MOS structures and the CO oxidation characteristics was found for both monolayer- and non-coated model catalysts. Furthermore, the devices exhibit retained MOS electrical output and CO oxidation characteristics as well as an unaffected catalyst surface composition, as confirmed by photoelectron spectroscopy, even after 200 h of continuous model catalyst operation. In addition to the implications on practical applicability of monolayer iron oxide coating on widely used polycrystalline Pt films in real-world catalysts and sensors, the findings also point to new possibilities regarding the use of MOS model systems for in situ characterization, high throughput screening, and tailoring of e.g. catalyst- and fuel-cell-electrode materials for specific applications. (C) 2016 Elsevier Inc. All rights reserved.

    The full text will be freely available from 2018-11-19 10:56
  • 49.
    Field, M. R.
    et al.
    RMIT University, Australia.
    Carlsson, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Partridge, J. G.
    RMIT University, Australia.
    McCulloch, D. G.
    RMIT University, Australia.
    McKenzie, D. R.
    University of Sydney, Australia.
    Bilek, M. M. M.
    University of Sydney, Australia.
    A combinatorial comparison of DC and high power impulse magnetron sputtered Cr2AlC2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 259, p. 746-750Article in journal (Refereed)
    Abstract [en]

    Using a combinatorial approach, Cr, Al and C have been deposited onto sapphire wafer substrates by High Power Impulse Magnetron Sputtering (HiPIMS) and DC magnetron sputtering. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and X-ray diffraction were employed to determine the composition and microstructure of the coatings and confirm the presence of the Cr2AlC MAX phase within both coatings. One location in both the DCMS and HiPIMS coatings contained only MAX phase Cr2AlC. The electrical resistivity was also found to be nearly identical at this location and close to that reported from the bulk, indicating that the additional energy in the HiPIMS plasma was not required to form high quality MAX phase Cr2AlC.

  • 50.
    Frodelius, Jenny
    et al.
    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.
    Beckers, Manfred
    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.
    Högberg, Hans
    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.
    Sputter deposition from a Ti2AlC target: Process characterization and conditions for growth of Ti2AlC2010In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 6, p. 1621-1626Article in journal (Refereed)
    Abstract [en]

    Sputter deposition from a Ti2AlC target was found to yield Ti-Al-C films with a composition that deviates from the target composition of 2:1:1. For increasing substrate temperature from ambient to 1000 degrees C, the Al content decreased from 22 at.% to 5 at.%, due to re-evaporation. The C content in as-deposited films was equal to or higher than the Ti content. Mass spectrometry of the plasma revealed that the Ti and Al species were essentially thermalized, while a large fraction of C with energies andgt;4 eV was detected. Co-sputtering with Ti yielded a film stoichiometry of 2:0.8:0.9 for Ti:Al:C, which enabled growth of Ti2AlC. These results indicate that an additional Ti flux balances the excess C and therefore provides for more stoichiometric Ti2AlC synthesis conditions.

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