A Raman imaging study of growth process of few-layer epitaxial graphene on vicinal 6H-SiC

Few-layer epitaxial graphenes grown on vicinal 6H-SiC (0001) were characterized by confocal Raman imaging. In the beginning of the growth, the surface of SiC substrate was covered with monolayer graphene. Next, few-layer graphenes started to grow toward directions perpendicular to [11-20] of the SiC substrate. The shift in the G-peak was not straightforward with the increase in number of graphene layers. This result can be interpreted that the in-plane compressive stress from the substrate depends on the domain size of graphene. The 2D-peak frequency shifted to higher frequency side due to strong compressive strain from the substrate with increasing of the growth times.