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Examples of Raman spectra of EG on SiC. Spectra are shown for the blank SiC (black squares) and for EG after a 28 min anneal at (red circles). The results of subtracting the background are shown using the blue triangle data markers. The D, G, and 2D band peaks are marked. Only the latter is not obscured by features in the SiC spectrum. Inset: example of a Lorentzian fit to determine the width and position of a 2D peak.
Variation of 2D peak position shift from that for freestanding exfoliated graphene of (squares) and calculated resulting strain values (triangles) as functions of UHV anneal time for an annealing temperature of . The dotted lines are the zeros of the two ordinate axes. The straight lines are linear fits to the data and have a reduced value of 0.928.
Variations in 2D peak position observed within each EG sample with varying anneal times. Inset: schematic showing the different sample areas (termed ranks) where data were taken on a SiC chip, with scans taken at random positions within each wide rank.
LEED images taken at different points from a sample annealed at for 28 min. (a) Image taken at 78 eV showing the typical graphene rings and SiC substrate spots, taken in the rank 1 or 2 region; (b) image taken at 183 eV showing a pregraphene reconstruction, taken in the rank 3 or 4 region. The LEED spot size is and so often crosses rank boundaries.
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