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  • 1.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Boosalis, A.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Zakharov, A. A.
    Lund University, Maxlab, Lund, Sweden.
    Hofmann, T.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Schubert, M.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Tiwald, T. E.
    J. A. Woollam Co., Lincoln, Nebraska, USA.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Large-area microfocal spectroscopic ellipsometry mapping of thickness and electronic properties of epitaxial graphene on Si- and C-face of 3C-SiC(111)2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 21, p. 213116-Article in journal (Refereed)
    Abstract [en]

    Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene grown by high-temperature sublimation on 3C-SiC (111) substrates is reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C-SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at ∼4.5 eV and the free-charge carrier scattering time, on the other are established. It is shown that the interface structure on the Si- and C-polarity of the 3C-SiC(111) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.

  • 2. Ellison, A.
    et al.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hemmingsson, Carl
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Magnusson, W.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Storasta, Liutauras
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Henelius, N.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    HTCVD Growth of Semi-Insulating 4H-SiC Crystals With Low Defect Density2001In: Mat. Res. Soc. Symp. Proc., Vol. 640, 2001, p. H1.2-Conference paper (Refereed)
  • 3.
    Eriksson, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Pearce, Ruth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gogova, Daniela
    Leibniz Institute of Crystal Growth, Berlin, Germany .
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Yakimova, Rositza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The influence of substrate morphology on thickness uniformity and unintentional doping of epitaxial graphene on SiC2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 24, p. 241607-Article in journal (Refereed)
    Abstract [en]

    A pivotal issue for the fabrication of electronic devices on epitaxial graphene on SiC is controlling the number of layers and reducing localized thickness inhomogeneities. Of equal importance is to understand what governs the unintentional doping of the graphene from the substrate. The influence of substrate surface topography on these two issues was studied by work function measurements and local surface potential mapping. The carrier concentration and the uniformity of epitaxial graphene samples grown under identical conditions and on substrates of nominally identical orientation were both found to depend strongly on the terrace width of the SiC substrate after growth.

  • 4.
    Hens, Philip
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. University of Marburg, Germany.
    Zakharov, Alexei A.
    Lund University, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Large area buffer-free graphene on non-polar (001) cubic silicon carbide2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 80, p. 823-829Article in journal (Refereed)
    Abstract [en]

    Graphene is, due to its extraordinary properties, a promising material for future electronic applications. A common process for the production of large area epitaxial graphene is a high temperature annealing process of atomically flat surfaces from hexagonal silicon carbide. This procedure is very promising but has the drawback of the formation of a buffer layer consisting of a graphene-like sheet, which is covalently bound to the substrate. This buffer layer degenerates the properties of the graphene above and needs to be avoided. We are presenting the combination of a high temperature process for the graphene production with a newly developed substrate of (0 0 1)-oriented cubic silicon carbide. This combination is a promising candidate to be able to supply large area homogenous epitaxial graphene on silicon carbide without a buffer layer. We are presenting the new substrate and first samples of epitaxial graphene on them. Results are shown using low energy electron microscopy and diffraction, photoelectron angular distribution and X-ray photoemission spectroscopy. All these measurements indicate the successful growth of a buffer free few layer graphene on a cubic silicon carbide surface. On our large area samples also the epitaxial relationship between the cubic substrate and the hexagonal graphene could be clarified.

  • 5.
    I Johansson, Leif
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Watcharinyanon, Somsakul
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, A.A.
    MAX-lab, Lund University, S-22100 Lund, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Detailed studies of graphene grown on C-face SiC2012In: Technical Proceedings of the 2012 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2012, 2012, p. 200-202Conference paper (Refereed)
    Abstract [en]

    Graphene samples were grown on the C-face of SiC, at high temperature in a furnace and an Ar ambient, and were investigated using LEEM, XPEEM, LEED, XPS and ARPES. Formation of fairly large grains (crystallographic domains) of graphene exhibiting sharp (1x1) patterns in μ-LEED was revealed and that different grains showed different azimuthal orientations. Selective area constant initial energy photoelectron angular distribution patterns recorded showed the same results, ordered grains and no rotational disorder between adjacent layers. A grain size of up to a few μm was obtained on some samples.

  • 6.
    Ivanov, Ivan Gueorguiev
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, Alexei A.
    Lund University, Sweden .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Layer-number determination in graphene on SiC by reflectance mapping2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 77, p. 492-500Article in journal (Refereed)
    Abstract [en]

    We report a simple, handy and affordable optical approach for precise number-of-layers determination of graphene on SiC based on monitoring the power of the laser beam reflected from the sample (reflectance mapping) in a slightly modified micro-Raman setup. Reflectance mapping is compatible with simultaneous Raman mapping. We find experimentally that the reflectance of graphene on SiC normalized to the reflectivity of bare substrate (the contrast) increases linearly with similar to 1.7% per layer for up to 12 layers, in agreement with theory The wavelength dependence of the contrast in the visible is investigated using the concept of ideal fermions and compared with existing experimental data for the optical constants of graphene. We argue also that the observed contrast is insensitive to the doping condition of the sample, as well as to the type of sample (graphene on C- or Si-face of 4H or 6H SiC, hydrogen-intercalated graphene). The possibility to extend the precise layer counting to similar to 50 layers makes reflectivity mapping superior to low-energy electron microscopy (limited to similar to 10 layers) in quantitative evaluation of graphene on the C-face of SiC. The method is applicable for graphene on other insulating or semiconducting substrates.

  • 7.
    Johansson, Leif I
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Watcharinyanon, Somsakul
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, A A
    Lund University.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Stacking of adjacent graphene layers grown on C-face SiC2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 12, p. 125405-Article in journal (Refereed)
    Abstract [en]

    Graphene was grown on the C-face of nominally on-axis SiC substrates using high-temperature sublimation with Ar as the buffer inert gas. The results of studies of the morphology, thickness, and electronic structure of these samples using low-energy electronmicroscopy (LEEM), x-ray photoelectron emission microscopy, photoelectron spectroscopy, angle-resolved photoelectron spectroscopy (ARPES), and low-energy electron diffraction (LEED) are presented. The graphene thickness is determined to vary from 1 or 2 to 6 or 7 monolayers (MLs), depending on the specific growth conditions utilized. The formation of fairly large grains (i.e., crystallographic domains) of graphene exhibiting sharp 1 x 1 spots in micro-LEED is revealed. Adjacent grains are found to show different azimuthal orientations. Macro-LEED patterns recorded mimic previously published, strongly modulated, diffraction ring LEED patterns, indicating contribution from several grains of different azimuthal orientations. We collected selected area constant initial energy photoelectron angular distribution patterns that show the same results. When utilizing a small aperture size, one Dirac cone centered on each of the six K-points in the Brillouin zone is clearly resolved. When using a larger aperture, several Dirac cones from differently oriented grains are detected. Our findings thus clearly show the existence of distinct graphene grains with different azimuthal orientations; they do not show adjacent graphene layers are rotationally disordered, as previously reported for C-face graphene. The graphene grain size is shown to be different on the different samples. In some cases, a probing area of 400 nm is needed to detect the grains. On one sample, a probing area of 5 mu m can be used to collect a 1 x 1 LEED pattern from a multilayer graphene grain. ARPES is used to determine the position of the Dirac point relative to the Fermi level on two samples that LEEM shows have dominant coverage of 2 and 3 MLs of graphene, respectively. The Dirac point is found to be located within 75 meV of the Fermi level on both samples, which indicates that the electron carrier concentration induced in the second and third graphene layers on the C-face is less than similar to 4x10(11) cm(-2). Formation of patches of silicate is revealed on some samples, but the graphene formed on such nonhomogenous surfaces can contain fairly large ordered multilayer graphene grains.

  • 8.
    Johansson, Leif
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Xia, Chao
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zarharov, Alexei A.
    MAX-lab, Lund University, Lund 22100, Sweden.
    Watcharinyanon, Somsakul
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC2013In: Crystals, ISSN 2073-4352, Vol. 3, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Graphene grown on C-face SiC substrates using two procedures, high and low growth temperature and different ambients, was investigated using Low Energy Electron Microscopy (LEEM), X-ray Photo Electron Electron Microscopy (XPEEM), selected area Low Energy Electron Diffraction (μ-LEED) and selected area Photo Electron Spectroscopy (μ-PES). Both types of samples showed formation of μm-sized grains of graphene. The sharp (1 × 1) μ-LEED pattern and six Dirac cones observed in constant energy photoelectron angular distribution patterns from a grain showed that adjacent layers are not rotated relative to each other, but that adjacent grains in general have different azimuthal orientations. Diffraction spots from the SiC substrate appeared in μ-LEED patterns collected at higher energies, showing that the rotation angle between graphene and SiC varied. C 1s spectra collected did not show any hint of a carbon interface layer. A hydrogen treatment applied was found to have a detrimental effect on the graphene quality for both types of samples, since the graphene domain/grain size was drastically reduced. From hydrogen treated samples, μ-LEED showed at first a clear (1 × 1) pattern, but within minutes, a pattern containing strong superstructure spots, indicating the presence of twisted graphene layers. The LEED electron beam was found to induce local desorption of hydrogen. Heating a hydrogenated C-face graphene sample did not restore the quality of the original as-grown sample.

  • 9.
    Karlsson, Mikael
    et al.
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden; Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden .
    Wang, Qin
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden.
    Zhao, Yichen
    Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Zhao, Wei
    Department of Sensor System, Acreo Swedish ICT AB, Box 1070, SE-16440 Kista, Sweden; Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Toprak, Muhammet S.
    Department of Materials and Nano Physics, KTH-Royal Institute of Technology, Kista, Sweden.
    Iakimov, Tihomir
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Ali, Amer
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Yakimova, Rositsa
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Syväjärvi, Mikael
    Graphensic AB, Mjärdevi Science Park, Teknikringen 1F, SE-58330 Linköping, Sweden.
    Ivanov, Ivan G.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Wafer-scale epitaxial graphene on SiC for sensing applications2015In: Micro+Nano Materials, Devices, and Systems / [ed] Benjamin J. Eggleton, Stefano Palomba, SPIE - International Society for Optical Engineering, 2015, Vol. 9668, p. 96685T-1-96685T-7Conference paper (Refereed)
    Abstract [en]

    The epitaxial graphene-on-silicon carbide (SiC-G) has advantages of high quality and large area coverage owing to a natural interface between graphene and SiC substrate with dimension up to 100 mm. It enables cost effective and reliable solutions for bridging the graphene-based sensors/devices from lab to industrial applications and commercialization. In this work, the structural, optical and electrical properties of wafer-scale graphene grown on 2’’ 4H semi-insulating (SI) SiC utilizing sublimation process were systemically investigated with focus on evaluation of the graphene’s uniformity across the wafer. As proof of concept, two types of glucose sensors based on SiC-G/Nafion/Glucose-oxidase (GOx) and SiC-G/Nafion/Chitosan/GOx were fabricated and their electrochemical properties were characterized by cyclic voltammetry (CV) measurements. In addition, a few similar glucose sensors based on graphene by chemical synthesis using modified Hummer’s method were also fabricated for comparison. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  • 10.
    Pallon, J.
    et al.
    Lund University, Sweden.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Wang, Q.
    ACREO Swedish ICT AB, Sweden.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphens AB, Teknikringen 1F, SE-58330 Linkoping, Sweden.
    Elfman, M.
    Lund University, Sweden.
    Kristiansson, P.
    Lund University, Sweden.
    Nilsson, E. J. C.
    Lund University, Sweden.
    Ros, L.
    Lund University, Sweden.
    Ion beam evaluation of silicon carbide membrane structures intended for particle detectors2016In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 371, p. 132-136Article in journal (Refereed)
    Abstract [en]

    Thin ion transmission detectors can be used as a part of a telescope detector for mass and energy identification but also as a pre-cell detector in a microbeam system for studies of biological effects from single ion hits on individual living cells. We investigated a structure of graphene on silicon carbide (SiC) with the purpose to explore a thin transmission detector with a very low noise level and having mechanical strength to act as a vacuum window. In order to reach very deep cavities in the SiC wafers for the preparation of the membrane in the detector, we have studied the Inductive Coupled Plasma technique to etch deep circular cavities in 325 mu m prototype samples. By a special high temperature process the outermost layers of the etched SiC wafers were converted into a highly conductive graphitic layer. The produced cavities were characterized by electron microscopy, optical microscopy and proton energy loss measurements. The average membrane thickness was found to be less than 40 mu m, however, with a slightly curved profile. Small spots representing much thinner membrane were also observed and might have an origin in crystal defects or impurities. Proton energy loss measurement (also called Scanning Transmission Ion Microscopy, STIM) is a well suited technique for this thickness range. This work presents the first steps of fabricating a membrane structure of SiC and graphene which may be an attractive approach as a detector due to the combined properties of SiC and graphene in a monolithic materials structure. (C) 2015 Elsevier B.V. All rights reserved.

  • 11.
    Pearce, Ruth
    et al.
    National Physical Laboratory, Teddington, UK.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Yakimova, Rositza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    On the Differing Sensitivity to Chemical Gating of Single and Double Layer Epitaxial Graphene Explored Using Scanning Kelvin Probe Microscopy2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 5, p. 4647-4656Article in journal (Refereed)
    Abstract [en]

    Using environmental scanning Kelvin probe microscopy we show that the position of the Fermi level of single layer graphene is more sensitive to chemical gating than that of double layer graphene. We calculate that the difference in sensitivity to chemical gating is not entirely due to the difference in band structure of 1 and 2 layer graphene. The findings are important for gas sensing where the sensitivity of the electronic properties to gas adsorption are monitored and suggest that single layer graphene could make a more sensitive gas sensor than double layer graphene. We propose that the difference in surface potential between adsorbate-free single and double layer graphene, measured using scanning kelvin probe microscopy, can be used as a non-invasive method of estimating substrate-induced doping in epitaxial graphene.

  • 12.
    Pearce, Ruth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Andersson, M
    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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Towards Optimisation of Epitaxially Grown Graphene Based Sensors for Highly Sensitive Gas Detection2010In: 2010 IEEE Sensors, Piscataway, NJ, United States: IEEE , 2010, p. 898-902Conference paper (Refereed)
    Abstract [en]

    Epitaxially grown single-layer and many-layer (10 atomic layers thick) resistive graphene devices were fabricated and compared for response towards NO2. Single-layer devices showed far greater sensitivity. The many-layer devices reduced in resistance on exposure to electron withdrawing NO2 demonstrating a majority hole carriers (p-type), whereas the single-layer device demonstrated an increase in resistance upon NO2 exposure demonstrating a majority of electron carriers (n-type). An n-p shift is observed for the single-layer device upon exposure to increasing concentrations of NO2. This shift is thought to be due to the reduction of electrons in the conduction band upon adsorption of electron-withdrawing NO2 making holes the majority carriers.

  • 13.
    Pearce, Ruth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Andersson, Mike
    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.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Epitaxially grown graphene based gas sensors for ultra sensitive NO(2) detection2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 155, no 2, p. 451-455Article in journal (Refereed)
    Abstract [en]

    Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO(2). Due to electron donation from SiC:, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO(2) detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO(2) indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO(2) making holes the majority carriers. (C) 2011 Elsevier B.V. All rights reserved.

  • 14.
    Raback, P
    et al.
    Ctr Sci Comp, FIN-02101 Espoo, Finland Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-17824 Ekero, Sweden Helsinki Univ Technol, Phys Lab, FIN-02015 Helsinki, Finland.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Nieminen, R
    Ctr Sci Comp, FIN-02101 Espoo, Finland Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden Okmet AB, SE-17824 Ekero, Sweden Helsinki Univ Technol, Phys Lab, FIN-02015 Helsinki, Finland.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Considerations on the crystal morphology in the sublimation growth of SiC2000In: Materials Science Forum, Vols. 338-343, Trans Tech Publications Inc., 2000, Vol. 338-3, p. 95-98Conference paper (Refereed)
    Abstract [en]

    In this paper the shape evolution of SiC source and seed is studied with simulations. Some basic geometries and temperature distributions are investigated. Also the condition for stable growth is discussed.

  • 15.
    Shtepliuk, Ivan I.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. NASU, Ukraine.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Lead (Pb) interfacing with epitaxial graphene2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 25, p. 17105-17116Article in journal (Refereed)
    Abstract [en]

    Here, we report the electrochemical deposition of lead (Pb) as a model metal on epitaxial graphene fabricated on silicon carbide (Gr/SiC). The kinetics of electrodeposition and morphological characteristics of the deposits were evaluated by complementary electrochemical, physical and computational methods. The use of Gr/SiC as an electrode allowed the tracking of lead-associated redox conversions. The analysis of current transients passed during the deposition revealed an instantaneous nucleation mechanism controlled by convergent mass transport on the nuclei locally randomly distributed on epitaxial graphene. This key observation of the deposit topology was confirmed by low values of the experimentally-estimated apparent diffusion coefficient, Raman spectroscopy and scanning electron microscopy (SEM) studies. First principles calculations showed that the nucleation of Pb clusters on the graphene surface leads to weakening of the interaction strength of the metal-graphene complex, and only spatially separated Pb adatoms adsorbed on bridge and/or edge-plane sites can affect the vibrational properties of graphene. We expect that the lead adatoms can merge in large metallic clusters only at defect sites that reinforce the metal-graphene interactions. Our findings provide valuable insights into both heavy metal ion electrochemical analysis and metal electroplating on graphene interfaces that are important for designing effective detectors of toxic heavy metals.

  • 16.
    Syväjärvi, Mikael
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Characterization of anisotropic step-bunching on as-grown SiC surfaces2000In: Materials Science Forum, Vols. 338-343, Trans Tech Publications Inc., 2000, Vol. 338-3, p. 375-378Conference paper (Refereed)
    Abstract [en]

    We report the presence of anisotropic step-bunching in SiC epitaxy on off-oriented substrates. This is an effect of step-flow growth. The anisotropic step-bunching is discussed in relation to the temperature dependence of lateral growth velocities and the interface roughness. The macrostep appearance is probably related to formation of morphologically stable faces with low surface free energy.

  • 17.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Gueorguie, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jacobson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Johansson, Leif
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Effect of High Temperature Annealing on Surface and Bulk Characteristics of 4H-SiC2001In: Proc. of the 43rd Electronic Material Conference, 2001Conference paper (Refereed)
  • 18.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Zakharov, A.
    MaxLab, Sweden .
    Boosalis, A.
    University of Nebraska, NE 68588 USA University of Nebraska, NE 68588 USA .
    Schubert, M.
    University of Nebraska, NE 68588 USA University of Nebraska, NE 68588 USA .
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Morphological and electronic properties of epitaxial graphene on SiC2014In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 439, p. 54-59Article in journal (Refereed)
    Abstract [en]

    We report on the structural and electronic properties of graphene grown on SiC by high-temperature sublimation. We have studied thickness uniformity of graphene grown on 4H-SiC (0 0 0 1), 6H-SiC (0 0 0 1), and 3C-SiC (1 1 1) substrates and investigated in detail graphene surface morphology and electronic properties. Differences in the thickness uniformity of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. It is also shown that a lower substrate surface roughness results in more uniform step bunching and consequently better quality of the grown graphene. We have compared the three SiC polytypes with a clear conclusion in favor of 3C-SiC. Localized lateral variations in the Fermi energy of graphene are mapped by scanning Kelvin probe microscopy It is found that the overall single-layer graphene coverage depends strongly on the surface terrace width, where a more homogeneous coverage is favored by wider terraces, It is observed that the step distance is a dominating, factor in determining the unintentional doping of graphene from the SiC substrate. Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene on 3C-SiC (1 1 1) is also reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C-SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at similar to 4.5 eV and the free-charge carrier scattering time, on the other are established It is shown that the interface structure on the Si- and C-polarity of the 3C-SiC (1 1 1) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.

  • 19.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobson, H
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Virojanadara, Chariya
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Johansson, Leif
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Impact of the initial surface conditions on defect appearance in 4H-SiC epilayers2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 283-286Conference paper (Refereed)
    Abstract [en]

    Effect of surface irregularities on defect nucleation and development in thick epitaxial layers of 4H-SiC has been investigated. It has been shown that during growth extended defects may undergo transformation and thus stacking faults can be formed, which is favored in thicker layers (e.g. 50mum). Network of misfit dislocations appears if the initial surface has a certain critical roughness and a lower surface energy. Evidence has been presented that well ordered graphite layer might form on the substrates during the preheating stage prior to growth via sublimation.

  • 20.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobsson, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Raback, P.
    Råback, P., Center for Scientific Computing, P.O. Box 405, FIN-02101 Espoo, Finland.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Growth of silicon carbide: Process-related defects2001In: Appl. Surf. Sci., Vol. 184, 2001, Vol. 184, no 1-4, p. 27-36Conference paper (Refereed)
    Abstract [en]

    This paper reviews the present understanding of defect formation and development in relation to process conditions in 4H-SiC crystal growth and epitaxy. The polytype uniformity during seeded sublimation growth of SiC boules has been discussed. Insight into different structural imperfections has been attempted. The role of the temperature distribution, as well as of the quality of seed/crystal interface in the occurrence of grown-in defects has been demonstrated. Micropipe termination by liquid-phase deposition along with defect evolution in subsequently grown layers due to rough interface has been addressed. Finally, a relation between extended morphological defects in thick (50-100 µm) 4H-SiC epitaxial layers and local stress in the material has been suggested. Optimised growth conditions to reduce the overall defect density have been proposed. © 2001 Elsevier Science B.V. All rights reserved.

  • 21.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobsson, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Raback, R
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Okmet AB, S-17824 Ekero, Sweden Ctr Comp Sci, FIN-02101 Espoo, Finland Okmet Ltd, FIN-01301 Vantaa, Finland.
    Vehanen, A
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Okmet AB, S-17824 Ekero, Sweden Ctr Comp Sci, FIN-02101 Espoo, Finland Okmet Ltd, FIN-01301 Vantaa, Finland.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Polytype stability in seeded sublimation growth of 4H-SiC boules2000In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 217, no 3, p. 255-262Article in journal (Refereed)
    Abstract [en]

    Process conditions for stable single polytype growth of 4H-SiC boules via a seeded sublimation technique have been developed. Reproducible results can be obtained in a narrow temperature interval around 2350 degrees C and on the C-face of 4H-SiC seeds. Evidence is presented that during the initial stage of growth, morphological instabilities may occur resulting in structural defects. A solution is proposed based on the experimental findings, i.e. the first regions of growth ought to be carried out at a low supersaturation (growth rate similar to 100 mu m/h) until a proper growth front has developed. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 22.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Okunev, AO
    Udal'tsov, VE
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Orientation-dependent defect formation in silicon carbide epitaxial layers2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 281-284Conference paper (Refereed)
    Abstract [en]

    Thick SiC epitaxial layers have been grown by sublimation on different initial surfaces in the range of 1800-2200degreesC. Evidences have been obtained that independently of the polytype and the surface polarity, there exists a transition region between the substrate and the epilayer in which the crystal structure is highly disturbed either by formation of misfit dislocations, predominantly in growth on vicinal (off-axis) surfaces or by domain boundaries and polytype transformation during growth on atomically flat (on-axis) surfaces. The transition layer thickness may vary from 15 to 50 mum and it seems to depend on the growth rate.

  • 23.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Challenges of Graphene Growth on Silicon Carbide2013In: ECS Transactions, Vol. 53, no 1, p. 9-16Article in journal (Refereed)
    Abstract [en]

    One of the main challenges in the fabrication of device quality graphene is the achievement of large area monolayer graphene that is processing compatible. Here, the impact of the substrate properties on the thickness uniformity and electronic characteristics for epitaxial graphene on SiC produced by high temperature sublimation has been evidenced and discussed. Several powerful techniques have been used to collect data, among them large scale ellipsometry mapping has been demonstrated for the first time. The study is covering all three SiC polytype, e.g. 4H-, 6H- and 3C-SiC in order to reveal eventual peculiarities that have to be controlled during graphene growth. The advantage of the cubic polytype is unambiguously demonstrated.

  • 24.
    Yazdi, G. Reza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Zakharov, A.
    Maxlab, Lund University, S-22100 Lund, Sweden.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Risitza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Growth of quality graphene on cubic silicon carbideManuscript (preprint) (Other academic)
    Abstract [en]

    The growth of epitaxial graphene was performed on the Si-face of 4H-SiC, 6H-SiC and 3C-SiC substrates by Si sublimation of SiC in Ar atmosphere at a temperature of 2000oC. Graphene surface morphology and thickness have been evaluated using low-energy electron microscopy (LEEM)  and  atomic  force  microscopy   (AFM).  Large  homogeneous   areas  of  graphene monolayers (over 50x50 μm2) have been successfully grown on 3C-SiC substrates. Differences in the morphology of graphene layers, grown on different SiC polytypes, are related to a large extent to minimization of the terrace surface energy during the step bunching process. The uniformity  of  Si  sublimation  is  a  decisive  factor  for  obtaining  large  area  homogeneous graphene. It is also shown that better quality graphene is grown on 3C-SiC substrates with smoother  surface,  because of less pronounced  step bunching  and lower distribution  of step heights on polished surface.

  • 25.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Epitaxial Graphene on SiC: A Review of Growth and Characterization2016In: Crystals, ISSN 2073-4352, Vol. 6, no 5, article id 53Article, review/survey (Refereed)
    Abstract [en]

    This review is devoted to one of the most promising two-dimensional (2D) materials, graphene. Graphene can be prepared by different methods and the one discussed here is fabricated by the thermal decomposition of SiC. The aim of the paper is to overview the fabrication aspects, growth mechanisms, and structural and electronic properties of graphene on SiC and the means of their assessment. Starting from historical aspects, it is shown that the most optimal conditions resulting in a large area of one ML graphene comprise high temperature and argon ambience, which allow better controllability and reproducibility of the graphene quality. Elemental intercalation as a means to overcome the problem of substrate influence on graphene carrier mobility has been described. The most common characterization techniques used are low-energy electron microscopy (LEEM), angle-resolved photoelectron spectroscopy (ARPES), Raman spectroscopy, atomic force microscopy (AFM) in different modes, Hall measurements, etc. The main results point to the applicability of graphene on SiC in quantum metrology, and the understanding of new physics and growth phenomena of 2D materials and devices.

  • 26.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, Alexei
    Lund University, Sweden .
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Growth of large area monolayer graphene on 3C-SiC and a comparison with other SiC polytypes2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 57, p. 477-484Article in journal (Refereed)
    Abstract [en]

    Epitaxial graphene growth was performed on the Si-terminated face of 4H-, 6H-, and 3C-SiC substrates by silicon sublimation from SiC in argon atmosphere at a temperature of 2000 degrees C. Graphene surface morphology, thickness and band structure have been assessed by using atomic force microscopy, low-energy electron microscopy, and angle-resolved photoemission spectroscopy, respectively. Differences in the morphology of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. The uniformity of silicon sublimation is a decisive factor for obtaining large area homogenous graphene. It is also shown that a lower substrate surface roughness results in more uniform step bunching with a lower distribution of step heights and consequently better quality of the grown graphene. Large homogeneous areas of graphene monolayers (over 50 x 50 mu m(2)) have been grown on 3C-SiC (1 1 1) substrates. The comparison with the other polytypes suggests a similarity in the surface behaviour of 3C- and 6H-SiC.

  • 27.
    Zakharov, Alexei
    et al.
    Max Lab, Lund University.
    Vinogradov, Nikolay A.
    MAXIV Laboratory, Lund University.
    Aprojanz, Johannes
    Technische Universität Chemnitz, Chemnitz, Germany.
    Nguyen, Thi Thuy Nhung
    Technische Universität Chemnitz, Chemnitz, Germany.
    Tegenkamp, Christoph
    Technische Universität Chemnitz, Chemnitz, Germany; Leibniz Universität Hannover, Hannover, Germany.
    Struzzi, Claudia
    Lund University, Lund, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Jokubavicius, Valdas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Wafer Scale Growth and Characterization of Edge Specific Graphene Nanoribbons for Nanoelectronics2019In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 2, no 1, p. 156-162Article in journal (Refereed)
    Abstract [en]

    One of the ways to use graphene in field effect transistors is to introduce a band gap by quantum confinement effect. That is why narrow graphene nanoribbons (GNRs) with width less than 50 nm are considered to be essential components in future graphene electronics. The growth of graphene on sidewalls of SiC(0001) mesa structures using scalable photolithography was shown to produce high quality GNRs with excellent transport properties. Such epitaxial graphene nanoribbons are very important in fundamental science but if GNRs are supposed to be used in advanced nanoelectronics, high quality thin (<50 nm) nanoribbons should be produced on a large (wafer) scale. Here we present a technique for scalable template growth of high quality GNRs on Si-face of SiC(0001) and provide detailed structural information along with transport properties. For the first time we succeeded now to avoid SiC-facet instabilities in order to grow high quality GNRs along both [11̅00] and [112̅0] crystallographic directions on the same substrate. The quality of the grown nanoribbons was confirmed by comprehensive characterization with atomic resolution STM, dark field LEEM, and transport measurements. This approach generates an entirely new platform for both fundamental and application driven research of quasi one-dimensional carbon based magnetism and spintronics.

1 - 27 of 27
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