Graphene formation on step-free 4H-SiC(0001)

Abstract

Step-free SiC was thermally decomposed in vacuum to better understand graphene formation in the absence of step fronts. Atomic force microscopy revealed graphene nucleating at surface pits that preferentially form along SiC{11¯00} planes. The density of these pits is 1×108cm-2, which is three orders of magnitude greater than the measured density of SiC threading dislocations. Additionally, Raman spectroscopy demonstrated that graphene on step-free regions have a redshifted 2D peak position and a smaller peak width than does graphene grown on stepped regions. This difference is attributed to film thickness, which is confirmed by cross-sectional transmission electron microscopy. Stepped regions have a graphitic film nearly 2 nm thick as compared to less than 0.7 nm for step-free regions.