Physical vapor deposition of metal nanoparticles on chemically modified graphene: Observations on metal-graphene interactions

摘要

The growth of metallic nanoparticles formed on chemically modified graphene (CMG) by physical vapor deposition is investigated. Fine control over the size (down to ～1.5 nm for Au) and coverage (up to 5 à- 10 ~4 Iμm ~(-2) for Au) of nanoparticles can be achieved. Analysis of the particle size distributions gives evidence for Au nanocluster diffusion at room temperature, while particle size statistics differ clearly between metal deposited on single- and multilayer regions. The morphology of the nanoparticles varies markedly for different metals (Ag, Au, Fe, Pd, Pt, Ti), from a uniform thin film for Ti to a droplet-like growth for Ag. A simple model explains these morphologies, based only on consideration of 1) the different energy barriers to surface diffusion of metal adatoms on graphene, and 2) the ratio of the bulk cohesive energy of the metal to the metal-graphene binding energy. Understanding these interactions is important for controlling nanoparticle and thin-film growth on graphene, and for understanding the resultant charge transfer between metal and graphene. Metal nanoparticle arrays on chemically modified graphene are fabricated by physical vapor deposition and characterized by transmission electron microscopy. Fine control over the nanoparticle size and density is achieved. The metal-graphene interactions are shown to dictate the resultant nanoparticle morphology, which in turn means that the nanoparticle morphology gives experimental insight into the energetics of the metal-graphene interface.