Ultrafast electron crystallography of heterogeneous structures: Gold-graphene bilayer and ligand-encapsulated nanogold on graphene

Here, we report studies of structures comprising a nanoscale gold-graphene bilayer and ligand-encapsulated nanogold on graphene multilayers. The observed time scale for the heating dynamics of the gold layer is significantly slower, when compared to previous results on free-standing gold films, and is independent of the level of carrier excitation. A model is proposed which incorporates the local carrier excitation in the gold layer, carrier relaxation in the graphene layer and heating of the gold layer by thermal conduction. When gold is isolated from graphene by ligand encapsulation, the carriers become again localized, consistent with the two phase description.