Abstract: 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.
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Johansson, L.I.; Xia, C.; Hassan, J.U.; Iakimov, T.; Zakharov, A.A.; Watcharinyanon, S.; Yakimova, R.; Janzén, E.; Virojanadara, C. Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC. Crystals 2013, 3, 1-13.
Johansson LI, Xia C, Hassan JU, Iakimov T, Zakharov AA, Watcharinyanon S, Yakimova R, Janzén E, Virojanadara C. Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC. Crystals. 2013; 3(1):1-13.
Johansson, Leif I.; Xia, Chao; Hassan, Jawad U.; Iakimov, Tihomir; Zakharov, Alexei A.; Watcharinyanon, Somsakul; Yakimova, Rositza; Janzén, Erik; Virojanadara, Chariya. 2013. "Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC." Crystals 3, no. 1: 1-13.