Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC

• Published in: Crystals (Basel) 2013-03, Vol.3 (1), p.1-13
• Main Authors: Johansson, Leif, Xia, Chao, Hassan, Jawad, Iakimov, Tihomir, Zakharov, Alexei, Watcharinyanon, Somsakul, Yakimova, Rositza, Janzén, Erik, Virojanadara, Chariya
• Format: Article
• Language: English
• Subjects: C-face graphene; hydrogen treatment; large grain sizes; layer registry; sublimation growth
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst3010001

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.