▎ 摘　　要

Few layer epitaxial graphenes (1.8-3.0 layers) grown on vicinal 6H-SiC (0001) were characterized by deep ultraviolet Raman spectroscopy. Shallow penetration depth of the probe laser enabled us to observe G-peak of graphene without subtraction of the SiC substrate signal from observed spectra. The G-peak was greatly shifted to higher frequency compared to that of graphite due to in-plane compressive stress deriving from the substrate. The frequency shift decreased with the number of graphene layers because of stress relaxation from layer to layer. Our experiment suggests that the stress is completely relaxed within five to six graphene layers. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3466150]