Coherent phonon dynamics in single-layer and multilayer graphene

Coherent phonon dynamics of single-layer graphene (SLG) and multi-layer graphene (MLG) on sapphire substrate were investigated using femtosecond pump-probe techniques. The center peak of G-mode phonon redshift with the number of graphene layer and the temperature increases in the temperature range between 300 K and 900 K. Also, the dephasing time upshift from 0.82 ps to 1.14 ps as the number of graphene layer increases. This results reflect thermal expansion and damping constant of SLG and MLG.