Size-dependent hot-phonon dynamics in graphene flakes
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We examine the ultrafast carrier phonon dynamics in graphene flakes with different lateral sizes. By using a size-selective centrifugation technique, we create graphene films with graphene flake sizes in the region of 120-450?nm. The transient transmission exhibits two-step relaxation, which are attributed to carrier thermalization followed by hot phonon cooling. We find that the cooling of the hot phonons proceeds faster, by a factor of three, for the smallest graphene flakes.
Applied Physics Letters
Nonlinear Optics and Spectroscopy