Effect of 6H-SiC (1120) substrate on epitaxial graphene revealed by Raman scattering

A nonpolar SiC(110) substrate has been used to fabricate epitaxial graphene (EG). Two EGs with layer numbers of 8-10 (referred to as MLG) and 2-3 (referred to as FLG) were used as representative to study the substrate effect on EG through temperature dependent Raman scattering. It is found that Raman lineshifts of G and 2D peaks of the MLG with temperature are consistent with that of a free graphene predicted by theory calculation, indicating that the substrate influence on the MLG is undetectable. While Raman G peak lineshifts of the FLG to that of the free graphene are obvious, however, its lineshift rate (-0.016 cm^-1/K) is almost one third of that (-0.043 cm^-1/K) of a EG on 6H-SiC (0001) in the temperature range from 300 K to 400 K, indicating a weak substrate effect from SiC (110) on the FLG. This renders the FLG a high mobility around 1812 cm²- ·V^-1·s^-1 at room temperature even with a very high carrier concentration about 2.95× 10¹³ cm^-2 (p-type). These suggest SiC (110) is more suitable for fabricating EG with high performance.