Thermal diffusivity of few-layers graphene measured by an all-optical method

We report on the measurement of the thermal diffusivity, D, of few-layers graphene obtained by chemical vapor deposition, using a noncontact optical microscopy method based on a mode mismatched thermal lens technique in a pump-probe two-laser beams configuration. It takes advantage of the coaxial counter propagating tightly focused excitation and collimated probe beams in an improved thermal lens microscopy setup. The obtained results: D = (6.5 ± 0.09) × 10^-4 m² s^-1, D = (1.9 ± 0.07) × 10^-4 m² s^-1 and D = (1.3 ± 0.05) × 10^-4 m² s^-1 for four (on a glass slide), eight and sixteen graphene (freestanding) layers are reasonable values, as can be concluded from reported literature data.