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  • 1.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Zhang, Zhibin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Defect formation in graphene during low-energy ion bombardment2016In: APL Materials, ISSN 2166-532X, Vol. 4, no 4, article id 046104Article in journal (Refereed)
    Abstract [en]

    This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.

  • 2. Alami, J.
    et al.
    Eklund, P.
    Emmerlich, J.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Högberg, H.
    Hultman, L.
    Helmersson, U.
    High-power impulse magnetron sputtering of Ti–Si–C thin films from a Ti3SiC2 compound target2006In: Thin Solids Films, ISSN 0040-6090, 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 direct-current magnetron sputtering under comparable conditions were rough and porous. We show that, due to the high degree of ionization of the sputtered species obtained in HIPIMS, the film composition, in particular the C content, depends on substrate inclination angle and Ar process pressure.

  • 3.
    Andersson, Anna M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Henningsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrochemically lithiated graphite characterised by photoelectron spectroscopy2003In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 119-121, p. 522-527Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) has been used to study the depth profile of the solid–electrolyte interphase (SEI) formed on a graphite powder electrode in a Li-ion battery. The morphology of the SEI-layer, formed in a 1 M LiBF4 EC/DMC 2:1 solution, consists of a 900 Å porous layer of polymers (polyethylene oxide) and a 15–20 Å thin layer of Li2CO3 and LiBF4 reduction–decomposition products. Embedded LiF crystals as large as 0.2 μm were found in the polymer matrix. LiOH and Li2O are not major components on the surface but rather found as a consequence of sputter-related reactions. Monochromatised Al Kα XPS-analysis based on the calibration of Ar+ ion sputtering of model compounds combined with a depth profile analysis based on energy tuning of synchrotron XPS can describe the highly complex composition and morphology of the SEI-layer.

  • 4.
    Andersson, Matilda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Högström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Urbonaite, Sigita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Furlan, Andrej
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Deposition and characterization of magnetron sputtered amorphous Cr-C films2012In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 9, p. 1408-1416Article in journal (Refereed)
    Abstract [en]

    Thin films in the Cr-C system with carbon content of 25-85 at.% have been deposited using non-reactive DC magnetron sputtering from elemental targets. Analyses with X-ray diffraction and transmission electron microscopy confirm that the films are completely amorphous. Also, annealing experiment show that the films had not crystallized at 500 degrees C. Furthermore, X-ray spectroscopy and Raman spectroscopy show that the films consist of two phases, an amorphous CrCx phase and an amorphous carbon (a-C) phase. The presence of two amorphous phases is also supported by the electrochemical analysis, which shows that oxidation of both chromium and carbon contributes to the total current in the passive region. The relative amounts of these amorphous phases influence the film properties. Typically, lower carbon content with less a-C phase leads to harder films with higher Young's modulus and lower resistivity. The results also show that both films have lower currents in the passive region compared to the uncoated 316L steel substrate. Finally, our results were compared with literature data from both reactively and non-reactively sputtered chromium carbide films. The comparison reveals that non-reactive sputtering tend to favour the formation of amorphous films and also influence e.g. the sp(2)/sp(3) ratio of the a-C phase. 

  • 5.
    Andersson, Matilda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Urbonaite, Sigita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetron sputtering of Zr-Si-C thin films2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 20, p. 6375-6381Article in journal (Refereed)
    Abstract [en]

    The phase composition and chemical bonding of Zr-C and Zr-Si-C films deposited by magnetron sputtering has been studied. The results show that the binary Zr-C films at higher carbon contents form nanocrystallites of ZrC in an amorphous carbon matrix. The addition of Si induces a complete amorphization of the films above a critical concentration of about 15 at.%. X-ray diffraction and transmission electron microscopy confirm that the amorphous films contain no nanocrystallites and therefore can be described as truly amorphous carbides. The amorphous films are thermally stable but start to crystallize above 500 degrees C. Analysis of the chemical bonding with X-ray photoelectron spectroscopy suggests that the amorphous films exhibit a mixture of different chemical bonds such as Zr-C, Zr-Si and Si-C and that the electrical and mechanical properties are dependent on the distribution of these bonds. For higher carbon contents, strong Si-C bonds are formed in the amorphous Zr-Si-C films making them harder than the corresponding binary Zr-C films.

  • 6.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Friction and contact resistance of nanocomposite Ti-Ni-C coatings2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 270, no 9-10, p. 555-566Article in journal (Refereed)
    Abstract [en]

    Ceramic nanocomposite coatings in the Ti-Ni-C were deposited using PVD and studied with respect to tribological properties and contact resistance. It was shown that coatings could be deposited combining of a low contact resistance and a low friction coefficient against silver, making them suitable for use in high performance electrical contacts.Nine coatings with different amounts of C and Ni were deposited. Coatings on flat Ni plated copper substrates were tested in a tribological ball-on-disc setup against ball bearing steel balls. Depending on primarily the amount of carbon the coatings showed very different friction coefficient and wear rate. The coatings were also deposited on cylindrical Ni plated copper substrates. Using geometrically identical silver plated cylinders as counter surface these were evaluated in a test setup better resembling a real life electrical contact. For most coatings a low electrical contact resistance was measured. The evolution of friction coefficient and contact resistance was correlated to wear marks and contact tracks, with their generated tribofilms, as examined after testing using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy.

  • 7.
    Bijelovic, Stojanka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Råsander, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wear-resistant magnetic thin film material based on a Ti1−xFexC1−y nanocomposite alloy2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 81, no 1, p. 014405-Article in journal (Refereed)
    Abstract [en]

    In this study we report on the film growth and characterization of thin films deposited on amorphous quartz. The experimental studies have been complemented by first-principles density-functional theory metastable Ti-Fe-C film changes. With increasing annealing time, there is a depletion of iron close to the surface of the film, while regions enriched in iron are simultaneously formed deeper into the film. Both the magnetic ordering temperature and the saturation magnetization changes significantly upon annealing. The DFT calculations show that the critical temperature and the magnetic moment both increase with increasing Fe and C-vacancy concentration. The formation of the metastable iron-rich Ti-Fe-C compound is reflected in the strong increase in the magnetic ordering temperature. Eventually, after enough annealing time nanocrystalline -Fe starts to precipitate, the amount and size of which can be controlled by the annealing procedure; after 20 min of annealing, the experimental results indicate a nanocrystalline iron-film embedded in a wear-resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single-crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material. approximately 50-nm-thick Ti-Fe-CDFT calculations. Upon annealing of as-prepared films, the composition of the10 min, nanocrystalline -Fe starts to precipitate, the amount and size of which can be controlled by the annealing procedure; after 20 min of annealing, the experimental results indicate a nanocrystalline iron-film embedded in a wear-resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single-crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material.

  • 8.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Di Cristo, Valentina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Conduction properties of graphene as a function of ion irradiation and acid treatment2011In: Graphene 2011 - 11th to 14th April 2011. Bilbao, Spain., 2011Conference paper (Refereed)
  • 9.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Quinlan, R A
    Holloway, B C
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An In-Situ Prepared Nano-Manipulator Tip for Electrical Characterization of Free Standing Graphene Like Sheets Inside a Focused Ion Beam/Scanning Electron Microscope2011In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 6, no 2, p. 162-168Article in journal (Refereed)
    Abstract [en]

    Although contacting and moving atoms has been demonstrated using probe techniques, for many nano-objects, a fast and reproducible nano-probe technique is needed to acquire a large number of electrical measurements on nano-objects that are often similar but not the identical. Nano-manipulators have become a common tool in many scanning electron microscopes (SEM) and focussed ion beam devices (FIB). They can be rapidly and reproducibly moved from one nano-object to another. In this work we present a procedure to obtain reproducible electrical measurements of nano- to micron-sized objects by using a sharp, tungsten tip with well defined surface properties. The tip is a part of a manipulator and is sharpened in-situ by using the gallium ion beam inside a focused ion beam/scanning electron microscope (FIB/SEM). The contact resistance between a Au surface and the tip is 70 kΩ before the sharpening procedure and 10 Ω after sharpening. The leakage current of the total set-up of 10pA makes it possible to measure currents through a variety of nano-objects. This measurement technique is applied to measure the resistance of as grown, water treated and two HCl treated carbon nanosheets (CNS). These CNS vary in size and morphology. Using this nano-contacting set-up, we could obtain measurements of more than 400 different CNS. The obtained histograms allow us to observe a clear decrease of the resistance between original and 3 hour acid treated CNSs. We observe that longer periods of exposure of the CNS to the HCl do not further modify the resistance.

  • 10.
    Boll, T.
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Thuvander, M.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Koch, S.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Wagner, J. N.
    Karlsruhe Inst Technol, KNMF, DE-76344 Eggenstein Leopoldshafen, Germany..
    Nedfors, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Stiller, K.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    An APT investigation of an amorphous Cr-B-C thin film2015In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 159, p. 217-222Article in journal (Refereed)
    Abstract [en]

    A magnetron sputtered amorphous Cr-B-C thin film was investigated by means of atom probe tomography (APT). The film is constituted of two phases; a Cr-rich phase present as a few nanometer large regions embedded in a Cr-poor phase (tissue phase). The Cr-rich regions form columnar chains oriented parallel to the growth direction of the film. It was found that the Cr-rich regions have a higher B:C ratio than the Cr-poor regions. The composition of the phases was determined as approximately 35Cr-33B-30C and 15Cr-40B-42C (at%), respectively. The results suggest that this type of nanocomposite films has a more complex structure than previously anticipated, which may have an importance for the mechanical and electrical properties.

  • 11.
    Dahlqvist, Martin
    et al.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden..
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rosen, Johanna
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden..
    Influence of boron vacancies on phase stability, bonding and structure of MB2 (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB2 type structure2015In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 43, article id 435702Article in journal (Refereed)
    Abstract [en]

    Transition metal diborides in hexagonal AlB2 type structure typically form stable MB2 phases for group IV elements (M = Ti, Zr, Hf). For group V (M = V, Nb, Ta) and group VI (M = Cr, Mo, W) the stability is reduced and an alternative hexagonal rhombohedral MB2 structure becomes more stable. In this work we investigate the effect of vacancies on the B-site in hexagonal MB2 and its influence on the phase stability and the structure for TiB2, ZrB2, HfB2, VB2, NbB2, TaB2, CrB2, MoB2, and WB2 using first-principles calculations. Selected phases are also analyzed with respect to electronic and bonding properties. We identify trends showing that MB2 with M from group V and IV are stabilized when introducing B-vacancies, consistent with a decrease in the number of states at the Fermi level and by strengthening of the B-M interaction. The stabilization upon vacancy formation also increases when going from M in period 4 to period 6. For TiB2, ZrB2, and HfB2, introduction of B-vacancies have a destabilizing effect due to occupation of B-B antibonding orbitals close to the Fermi level and an increase in states at the Fermi level.

  • 12. Eklund, P
    et al.
    Emmerlich, J
    Högberg, H
    Wilhelmsson, Ola
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Isberg, P
    Birch, J
    Persson, P. O. Å.
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Hultman, L
    Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films2005In: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 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.

  • 13. Eklund, Per
    et al.
    Beckers, Manfred
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Högberg, Hans
    Hultman, Lars
    The Mn + 1AXn 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.

  • 14. Eklund, Per
    et al.
    Dahlqvist, Martin
    Tengstrand, Olof
    Hultman, Lars
    Lu, Jun
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rosen, Johanna
    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.

  • 15. Emmerlich, Jens
    et al.
    Högberg, Hans
    Sasvári, Szilvia
    Persson, Per O. Å
    Hultman, Lars
    Palmquist, Jens-Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Molina-Aldareguia, Jon M
    Czigány, Zsolt
    Growth of Ti3SiC2 thin films by elemental target magnetron sputtering2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 9, p. 4817-4826Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2(0001) thin films have been deposited by dc magnetron sputtering from three elemental targets of Ti, C, and Si onto MgO(111) and Al2O3(0001) substrates at temperatures of 800–900 °C. This process allows composition control to synthesize Mn + 1AXn (MAX) phases (M: early transition metal; A: A-group element; X: C and/or N; n = 1–3) including Ti4SiC3. Depositions on MgO(100) substrates yielding the Ti–Si–C MAX phases with (105), as the preferred orientation. Samples grown at different substrate temperatures, studied by means of transmission electron microscopy and x-ray diffraction investigations, revealed the constraints of Ti3SiC2 nucleation due to kinetic limitations at substrate temperatures below 700 °C. Instead, there is a competitive TiCx growth with Si segregation to form twin boundaries or Si substitutional incorporation in TiCx. Physical properties of the as-deposited single-crystal Ti3SiC2 films were determined. A low resistivity of 25 µ cm was measured. The Young's modulus, ascertained by nanoindentation, yielded a value of 343–370 GPa. For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost 30 GPa. With increased maximum indentation loads, the hardness was observed to decrease toward bulk values as the characteristic kink formation sets in with dislocation ordering and delamination at basal planes.

  • 16. Emmerlich, Jens
    et al.
    Music, Denis
    Eklund, Per
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Schneider, Jochen M.
    Högberg, Hans
    Hultman, Lars
    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.

  • 17. ENGQVIST, J
    et al.
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    INITIAL-STAGES OF GROWTH DURING CVD OF W ON TISI2 SUBSTRATES1995In: Thin Solid Films, Vol. 263, no 1, p. 54-64Article in journal (Refereed)
    Abstract [en]

    The initial stages of growth in chemical vapour deposition (CVD) of W from WF6 have been studied in an ultra-high vacuum system using CVD TiSi2 films as substrates. The influence of different surface conditions on the substrate-reduction process was inve

  • 18.
    Fang, C.M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hultman, L.
    General trend of the mechanical properties of the ternary carbides M3SiC2 (M=transition metal)2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 5, p. 054106-Article in journal (Refereed)
    Abstract [en]

    We present results from first-principles calculations of ternary transition metal carbides in the M3SiC2 series (where M=early transition metal). We predict structural and mechanical properties of these new MN+1AXN phases. The bulk modulus of the ternary carbides, M3SiC2, are in the calculations found to be proportional to the bulk modulus of the corresponding binary carbides, MC. We have analyzed this behavior using a simple, nearest-neighbor bond model, as well as from first-principles total energy calculations and have found that it is caused by a considerably weaker M-Si bond compared to the M-C bond.

  • 19.
    Folkenant, Matilda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nygren, Kristian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Malinovskis, Paulius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Palisaitis, Justinas
    Persson, Per
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Structure and properties of Cr-C/Ag films deposited by magnetron sputtering2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 281, p. 184-192Article in journal (Refereed)
    Abstract [en]

    Cr-C/Ag thin films with 0-14 at% Ag have been deposited by magnetron sputtering from elemental targets. The samples were analyzed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to study their structure and chemical bonding. A complex nanocomposite structure consisting of three phases; nanocrystalline Ag, amorphous CrCx and amorphous carbon is reported. The carbon content in the amorphous carbide phase was determined to be 32-33 at% C, independent of Ag content Furthermore, SEM and XPS results showed higher amounts of Ag on the surface compared to the bulk. The hardness and Young's modulus were reduced from 12 to 8 GPa and from 270 to 170 GPa, respectively, with increasing Ag content. The contact resistance was found to decrease with Ag addition, with the most Ag rich sample approaching the values of an Ag reference sample. Initial tribological tests gave friction coefficients in the range of 0.3 to 0.5, with no clear trends. Annealing tests show that the material is stable after annealing at 500 degrees C for 1 h, but not after annealing at 800 degrees C for 1 h. In combination, these results suggest that sputtered Cr-C/Ag films could be potentially applicable for electric contact applications.

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

    We investigate the amorphous structure, chemical bonding, and electrical properties of magnetron sputtered Fe1-xCx (0.21 <= x <= 0.72) thin films. X-ray, electron diffraction and transmission electron microscopy show that the Fe1-xCx films are amorphous nanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeCy, and a carbon-rich matrix. Pair distribution function analysis indicates a close-range order similar to those of crystalline Fe3C carbides in all films with additional graphene-like structures at high carbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we find that the amorphous carbidic phase has a composition of 15-25 at% carbon that slightly increases with total carbon content. X-ray absorption spectra exhibit an increasing number of unoccupied 3d states and a decreasing number of C 2p states as a function of carbon content. These changes signify a systematic redistribution in orbital occupation due to charge-transfer effects at the domain-size-dependent carbide/matrix interfaces. The four-point probe resistivity of the Fe1-xCx films increases exponentially with carbon content from similar to 200 mu Omega cm (x = 0.21) to similar to 1200 mu Omega cm (x = 0.72), and is found to depend on the total carbon content rather than the composition of the carbide. Our findings open new possibilities for modifying the resistivity of amorphous thin film coatings based on transition metal carbides through the control of amorphous domain structures.

  • 21.
    Furlan, Andrej
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lu, Jun
    Hultman, Lars
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Control of crystallinity in sputtered Cr-Ti-C films2013In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 61, no 17, p. 6352-6361Article in journal (Refereed)
    Abstract [en]

    The influence of Ti content on crystallinity and bonding of Cr-Ti-C thin films deposited by magnetron sputtering have been studied by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. Our results show that binary Cr-C films without Ti exhibit an amorphous structure with two non-crystalline components; amorphous CrCx, and amorphous C (a-C). The addition of 10-20 at.% Ti leads to the crystallization of the amorphous CrCx and the formation of a metastable cubic (Cr1-xTix)Cy phase. The observation was explained based on the tendency of the 3d transition metals to form crystalline carbide films. The mechanical properties of the films determined by nanoindentation and microindentation were found to be strongly dependent on the film composition in terms of hardness, elasticity modulus, hardness/elasticity ratio and crack development.

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

    The crystal structure and chemical bonding of magnetron-sputtering deposited nickel carbide Ni1-xCx (0.05 <= x <= 0.62) thin films have been investigated by high-resolution x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and soft x-ray absorption spectroscopy. By using x-ray as well as electron diffraction, we found carbon-containing hcp-Ni (hcp-NiCy phase), instead of the expected rhombohedral-Ni3C. At low carbon content (4.9 at%), the thin film consists of hcp-NiCy nanocrystallites mixed with a smaller amount of fcc-NiCx. The average grain size is about 10-20 nm. With the increase of carbon content to 16.3 at%, the film contains single-phase hcp-NiCy nanocrystallites with expanded lattice parameters. With a further increase of carbon content to 38 at%, and 62 at%, the films transform to x-ray amorphous materials with hcp-NiCy and fcc-NiCx nanodomain structures in an amorphous carbon-rich matrix. Raman spectra of carbon indicate dominant sp(2) hybridization, consistent with photoelectron spectra that show a decreasing amount of C-Ni phase with increasing carbon content. The Ni 3d-C 2p hybridization in the hexagonal structure gives rise to the salient double-peak structure in Ni 2p soft x-ray absorption spectra at 16.3 at% that changes with carbon content. We also show that the resistivity is not only governed by the amount of carbon, but increases by more than a factor of two when the samples transform from crystalline to amorphous.

  • 23.
    Grandin, Martina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ti-Ni-C nanocomposite coatings evaluated in a sliding electrical contact application2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 276, p. 210-218Article in journal (Refereed)
    Abstract [en]

    Nanocomposite Ti-Ni-C coatings, with nanosized carbide grains in an amorphous carbon (a-C) matrix have been suggested to have low friction and low contact resistance making them suitable for sliding electrical contacts. In this study we investigate further the previously observed influence of the amount of amorphous carbon, in a test set-up simulating instrumentation and control applications. The tribological and electrical performance is evaluated at high speed and continuous sliding against silver-graphite, where the mechanical load and current are fairly low. It is shown that under these circumstances there is no significant influence from the amount of a-C on neither the contact resistance nor the amount of wear of the silver-graphite. The reason for this is suggested to be that similar tribofilms are formed on the surface of the coatings, regardless of the amount of a-C phase. Degradation of the nanocomposite coatings is observed under electrical load, even though they are both much harder than the silver-graphite counter surface.

  • 24.
    Grechnev, Alexei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, Sa
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Layered compound Nb3SiC2 predicted from first-principles theory2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 15, p. 3071-3073Article in journal (Refereed)
    Abstract [en]

    A previously unobserved ternary carbide, Nb3SiC2, belonging to the family of the so-called Mn+1AXn or MAX phases is predicted from first-principles calculations. It has a theoretical bulk modulus of 296 Gpa, wich is much higher than that of Ti3SiC2. The new phase is metastable with a formation energy of +0.02 eV/atom. We suggest that the phase may possibly be synthesized using thin film technology. The chemical binding of Nb3SiC2 is investigated using the balanced crystal orbital overlap population indicator and it is found to be dominated by the formation of Nb4D-C 2p covalent bonds.

  • 25.
    Grennberg, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Synthesis of graphene and derivatives2012In: Advanced Functional Materials: A Perspective from Theory and Experiment / [ed] Biplab Sanyal and Olle Eriksson, Elsevier, 2012, no 1, p. 105-127Chapter in book (Refereed)
  • 26.
    Grennberg, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Alm, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Functionalization and Area-Selective Deposition of Magnetic Carbon-Coated Iron Nanoparticles from Solution2011In: Journal of Nanotechnology, ISSN 1687-9503, p. 342368-Article in journal (Refereed)
    Abstract [en]

    A route to area-selective deposition of carbon-coated iron nanoparticles, involving chemical modification of the surface of the particles, is described. Partial oxidative etching of the coating introduces carboxylic groups, which then are esterified. The functionalized particles can be selectively deposited on the Si areas of Si/SiO2 substrates by a simple dipping procedure. Nanoparticles and nanoassemblies have been analyzed using SEM, TEM, and XPS.

  • 27. Hogberg, H
    et al.
    Tagtstrom, P
    Lu, J
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Chemical vapour deposition of tungsten carbides on tantalum and nickel substrates1996In: Thin Solid Films, Vol. 272, no 1, p. 116-123Article in journal (Refereed)
    Abstract [en]

    Tungsten carbide films have been deposited by low-pressure chemical vapour deposition from a WF6/H-C3(8)/H-2 mixture on Ta and Ni substrates. Single-phase WC films could be deposited on Ta in a broad vapour composition range at 900 degrees C. A mixture o

  • 28.
    Hugosson, H. W
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Ruban, A. V
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Abrikosov, I. A
    Surface energies and work functions of the transition metal carbides2004In: Surface Science, Vol. 557, no 1-3, p. 243-254Article in journal (Refereed)
    Abstract [en]

    We have performed an ab initio study of the surface energies, surface electronic structures and work functions for the (1 0 0) surface of the, existent and hypothetical, cubic 3d (Sc–Cu), 4d (Zr–Ag) and 5d (La–Au) transition metal carbides. The calculated surface energies have been compared to predictions using a so-called bond-cutting model and a model based on the so-called bonding energies. The absolute values and rough trends of the surface energies are fairly well predicted within the simple bond-cutting model, as compared to fully self-consistent calculations, while both trends and absolute values are well reproduced within the bonding energy model. The electronic structure (densities of states) of the transition metal carbides at the surface and in the bulk have been calculated. The trends are discussed in relation to the behavior of the surface energy and the work function across the series.

  • 29.
    Hugosson, HW
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, O
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Johansson, B
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Phase stabilities and homogeneity ranges in 4d-transition-metal carbides: A theoretical study - art. no. 1341082001In: PHYSICAL REVIEW B, ISSN 0163-1829, Vol. 63, no 13, p. 134108-Article in journal (Refereed)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the 4d-transition-metal cal bides ZrC, NbC, and MoC. The experimental phase diagrams at T = 0 of the refractory compounds ZrC, NbC, and MoC have been reproduced

  • 30. Hugosson, HW
    et al.
    Eriksson, O
    Nordstrom, L
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Fast, L
    Delin, A
    Wills, JM
    Johansson, B
    Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide1999In: JOURNAL OF APPLIED PHYSICS, ISSN 0021-8979, Vol. 86, no 7, p. 3758-3767Article in journal (Other scientific)
    Abstract [en]

    First principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic delta(NaCl) phase and the three hexagonal gamma(WC), eta and gamma'(TiAs) phases. The effect of vacancie

  • 31.
    Hugosson, H.W
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Abrikosov, I.A
    Surface segregation of transition metal impurities on the TiC(100) Surface2005In: Surface Science, Vol. 585, p. 101-107Article in journal (Refereed)
    Abstract [en]

    The segregation energies of 3d (Sc–Cu), 4d (Y–Ag) and 5d (La–Au) transition metal impurities on the (1 0 0) surface of TiC have been obtained using first-principles electronic structure calculations. The results are in agreement with available experimental data and show that the difference in atomic size between the impurity and host species, as well as the difference in surface energies determines if the impurity will segregate towards the surface or not. The results indicate that the difference in size is the dominant factor for the trends in segregation of transition metal impurities towards the (1 0 0) surface of TiC.

  • 32.
    Hugosson, HW
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Johansson, B
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, O
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Phase stability diagrams of transition metal carbides, a theoretical study2001In: CHEMICAL PHYSICS LETTERS, ISSN 0009-2614, Vol. 333, no 6, p. 444-450Article in journal (Refereed)
    Abstract [en]

    The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand, for example, the differences and changes in homogeneity ranges found in these systems. This determination of relative phase stabilities for a wide range of concentrations is necessary for first principles determination of phase diagrams for these compounds with complex bonding and structural properties as well as technological importance.

  • 33.
    Hugosson, HW
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Korzhavyi, P
    Jansson, Ulf
    Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Johansson, B
    Eriksson, O
    Phase stabilities and structural relaxations in substoichiometric TiC1-x2001In: PHYSICAL REVIEW B, ISSN 0163-1829, Vol. 6316, no 16, p. 165116-Article in journal (Refereed)
    Abstract [en]

    First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1-x. The effect of relaxation on phase stabilities, equilibrium volumes. and electronic structure of the substoic

  • 34.
    Hugosson, Håkan W.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Theoretical studies of substitutional impurities in molybdenum carbide1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 22, p. 15123-15130Article in journal (Refereed)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.

  • 35.
    Högberg, H
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Birch, J
    Johansson, M
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Hultman, L
    Strain relaxation in low-temperature deposited epitaxial titanium carbide films2000In: Journal of Crystal Growth, Vol. 219, p. 237-244Article in journal (Refereed)
  • 36.
    Högberg, H.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Birch, J.
    Johansson, M.P.
    Hultman, L.
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Deposition of Epitaxial Transition Metal Films and Superlattices by DC Magnetron Sputtering and C60 Evaporation2001In: J. Mater. Res., no 63, p. 633-Article in journal (Refereed)
  • 37. Högberg, H
    et al.
    Emmerlich, J
    Eklund, P
    Wilhelmsson, Ola
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Palmquist, J-P
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Hultman, L
    Growth and Property Characterization of Epitaxial MAX-Phase Thin Films from the Tin+1(Si, Ge, Sn)Cn Systems2006In: Advances in Science and Technology, Vol. 45, p. 2648-2655Article in journal (Refereed)
  • 38. Högberg, H
    et al.
    Hultman, L
    Emmerlich, J
    Joelsson, T
    Eklund, P
    Molina-Aldareguia, J.M
    Palmquist, J.-P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Wilhelmsson, Ola
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Growth and characterization of MAX-phase thin films2005In: Surface and Coatings Technology, Vol. 193, p. 6-10Article in journal (Refereed)
    Abstract [en]

    We report that magnetron sputtering can be applied to synthesize MAX-phase films of several systems including Ti–Si–C, Ti–Ge–C, Ti–Al–C, and Ti–Al–N. In particular, epitaxial films of the known phases Ti3SiC2, Ti3GeC2, Ti2GeC, Ti3AlC2, Ti2AlC, and Ti2AlN as well as the newly discovered thin film phases Ti4SiC3, Ti4GeC3 and intergrown structures can be deposited at 900–1000 °C on Al2O3(0001) and MgO(111) pre-seeded with TiC or Ti(Al)N. From XTEM and AFM we suggest a growth and nucleation model where MAX-phase nucleation is initiated at surface steps or facets on the seed layer and followed by lateral growth. Differences between the growth behavior of the systems with respect to phase distribution and phase stabilities are discussed. Characterization of mechanical properties for Tin+1Si–Cn films with nanoindentation show decreased hardness from about 25 to 15 GPa upon penetration of the basal planes with characteristic large plastic deformation with pile up dependent on the choice of MAX material. This is explained by cohesive delamination of the basal planes and kink band formation, in agreement with the observations made for bulk material. Measurements of the electrical resistivity for Ti–Si–C and Ti–Al–N films with four-point probe technique show values of 30 and 39 μΩ cm, respectively, comparable to bulk materials.

  • 39.
    Högberg, Hans
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Birch, J
    Johansson, M
    Hultman, L
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Growth, structure and mechanical properties of transition metal carbide superlattices2001In: Journal of Materials Research, Vol. 16, p. 1301-Article in journal (Refereed)
  • 40. Högberg, Hans
    et al.
    Emmerlich, Jens
    Eklund, Per
    Wilhelmsson, Ola
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Palmquist, Jens-Petter
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hultman, Lars
    Growth and characterization of epitaxial MAX-phase thin films from the Tin+1(Si,Ge,Sn)Cn systems2006In: 11th International Ceramics Congress, CIMTEC (2006 : Acireale, Italy), 2006, p. 2648-2655Conference paper (Refereed)
  • 41.
    Högberg, Hans
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry.
    Malm, JO
    Talyzin, A
    Norin, L
    Lu, J
    Jansson, Ulf
    Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Deposition of transition metal carbides and superlattices using C-60 as carbon source2000In: JOURNAL OF THE ELECTROCHEMICAL SOCIETY, ISSN 0013-4651, Vol. 147, no 9, p. 3361-3369Article in journal (Refereed)
    Abstract [en]

    Thin films of TiC, VC, and NbC have been deposited on MgO(001) by coevaporation of the metals and C-60 It was found that these metals induced a decomposition of the C-60 molecule and that carbide films can be formed at a temperature as low as 100 degrees

  • 42.
    Högström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Matilda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    On the evaluation of corrosion resistances of amorphous chromium carbide thin-films2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 122, no SI, p. 224-233Article in journal (Refereed)
    Abstract [en]

    The possibilities of evaluating the corrosion resistance of amorphous chromium carbide (Cr-C) films containing nanometre-sized carbide grains embedded in an amorphous carbon matrix on the basis of polarization curves, voltammograms and the oxidation charge have been studied for Cr-C films with different carbon concentrations. The films, which were manufactured by non-reactive directcurrent magnetron sputtering, were studied in 1.0 mM H2SO4 at both 22 °C and 80 °C, and with scanning electron microscopy and X-ray photoelectron spectroscopy prior to and after the electrochemical experiments. It is demonstrated that the oxidation of these Cr-C films gives rise to a surface composed of Cr2O3 and partially oxidized carbon and that the non-corroding oxidation current due to the carbon oxidation increases with increasing carbon concentration in the films as well as with the electrolyte temperature. Since the oxidation current is composed of contributions from both Cr-C and carbon oxidation it is not straightforward to evaluate the corrosion resistances of these films based on the current in the passive region, the mixed potential (i.e., the corrosion potential) or the open circuit potential. The present results in fact indicate that Cr-C films with high carbon concentrations may have better corrosion resistances than the corresponding films with lower carbon concentrations although larger currents in the passive region can be seen in polarization curves.

  • 43.
    Isaeva, Leyla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mukherjee, Soham
    Indian Institute of Science.
    Pelliccione, Christopher J.
    Illinois Institute of Technology.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Segre, Carlos U
    Illinois Institute of Technology.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sarma, D. D.
    Indian Institute of Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kádas, Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Amorphous W-S-N thin films: the atomic structure behind ultra-low friction2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 82, p. 84-93Article in journal (Refereed)
    Abstract [en]

    Amorphous W–S–N in the form of thin films has been identified experimentally as an ultra-low friction material, enabling easy sliding by the formation of a WS2 tribofilm. However, the atomic-level structure and bonding arrangements in amorphous W–S–N, which give such optimum conditions for WS2 formation and ultra-low friction, are not known. In this study, amorphous thin films with up to 37 at.% N are deposited, and experimental as well as state-of-the-art ab initio techniques are employed to reveal the complex structure of W–S–N at the atomic level. Excellent agreement between experimental and calculated coordination numbers and bond distances is demonstrated. Furthermore, the simulated structures are found to contain N bonded in molecular form, i.e. N2, which is experimentally confirmed by near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy analysis. Such N2 units are located in cages in the material, where they are coordinated mainly by S atoms. Thus this ultra-low friction material is shown to be a complex amorphous network of W, S and N atoms, with easy access to W and S for continuous formation of WS2 in the contact region, and with the possibility of swift removal of excess nitrogen present as N2 molecules.

  • 44. Isberg, P
    et al.
    Hultman, T
    Liljenberg, L
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    A new compound reduces contact wear2004In: ABB Review, no 1, p. 64-66Article in journal (Refereed)
  • 45.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Biplab, Sanyal
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Quinlan, Ronald A.
    Holloway, Brian C.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Electrical characterization of defect induced graphene nanosheets2009In: Nanotech Europe 2009 - 28-30 september Berlin, 2009Conference paper (Refereed)
  • 46.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Sanyal, Biplab
    Fransson, Jonas
    Eriksson, Olle
    Jansson, Ulf
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    The effect of induced vacancy defects on resistivity of graphene2009In: Scandem conference, Reykjavik 2009, 2009Conference paper (Refereed)
  • 47.
    Jafri, Syed Hassan Mujtaba
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Quinlan, Ronald A
    College of William and Mary, Williamsburg VA, USA.
    Holloway, Brian C
    Luna Innovations, Danville, VA, USA.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Conductivity engineering of graphene by defect formation2010In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 43, no 4, p. 045404-Article in journal (Refereed)
    Abstract [en]

    Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behaviour around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.

  • 48.
    Jansson, U
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Högberg, H
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Palmqvist, JP
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Norin, L
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Malm, JO
    Hultman, L
    Birch, J
    Low-temperature epitaxial growth of metal carbides using fullerenes2001In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 142-144, p. 817-822Article in journal (Refereed)
    Abstract [en]

    Epitaxial transition metal carbides can be deposited at low temperatures by simultaneous evaporation of C60 and either metal e-beam evaporation or metal d.c. magnetron sputtering. Hitherto, epitaxial films of TiC, VC, NbC, MoC, W2C and WC have been deposited on MgO(100), MgO(111) and in some cases 6H- and 4H-SiC(0001). Epitaxial TiC films with a good quality have been deposited at temperatures as low as 100°C with metal sputtering, while somewhat higher temperatures (>200°C) are required for the other metals. In general, the plasma-assisted process allows lower deposition temperatures than the co-evaporation process. Most carbides can be deposited in a wide range of compositions within their homogeneity ranges by a fine-tuning of the Me/C60 flux. However, the results suggest that the formation of free surface carbon can be a limiting factor. The processes have also been used to deposit superlattices of TiC/NbC and TiC/VC at 400–500°C as well as epitaxial ternary TixV1−xCy films. Furthermore, epitaxial films of ternary carbides with well-controlled metal concentration profiles can be deposited at temperatures below 500°C.

  • 49.
    Jansson, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sputter deposition of transition-metal carbide films - A critical review from a chemical perspective2013In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 536, p. 1-24Article, review/survey (Refereed)
    Abstract [en]

    Thin films based on transition-metal carbides exhibitmany interesting physical and chemical properties making them attractive for a variety of applications. The most widely used method to produce metal carbide films with specific properties at reduced deposition temperatures is sputter deposition. A large number of papers in this field have been published during the last decades, showing that large variations in structure and properties can be obtained. This review will summarise the literature on sputter-deposited carbide films based on chemical aspects of the various elements in the films. By considering the chemical affinities (primarily towards carbon) and structural preferences of different elements, it is possible to understand trends in structure of binary transition-metal carbides and the ternary materials based on these carbides. These trends in chemical affinity and structure will also directly affect the growth process during sputter deposition. A fundamental chemical perspective of the transition-metal carbides and their alloying elements is essential to obtain control of the material structure (from the atomic level), and thereby its properties and performance. This review covers a wide range of materials: binary transition-metal carbides and their nanocomposites with amorphous carbon; the effect of alloying carbide-based materials with a third element (mainly elements from groups 3 through 14); as well as the amorphous binary and ternary materials from these elements deposited under specific conditions or at certain compositional ranges. Furthermore, the review will also emphasise important aspects regarding materials characterisation which may affect the interpretation of data such as beam-induced crystallisation and sputter-damage during surface analysis. 

  • 50.
    Jansson, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Råsander, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    André, Benny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Design of carbide-based nanocomposite thin films by selective alloying2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 4, p. 583-590Article in journal (Refereed)
    Abstract [en]

    This paper reviews a series of studies on alloying of sputtered TiC coatings with weak carbide-forming metals, Me, such as Al, Fe, Ni, Pt and Cu. Metastable solid solutions with Me on the Ti sites are easily obtained by magnetron sputtering at low temperatures (< 300 °C). First principles density functional theory (DFT) calculations of such carbides show that a driving force exists to remove carbon from the structure as an alternative and kinetically more favourable route compared to Me precipitation. This leads to a situation where additional control of the phase composition is given by annealing: both direct influence during film growth, as well as through subsequent annealing. Thus, alloying of the nanocomposite with weak carbide-forming metals can be used to tune many mechanical, electric and magnetic properties of a carbide-based nanocomposite film.

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