Coalescence kinetics of copper clusters on highly oriented pyrolytic graphite and Dow Cyclotene, as determined by x-ray photoelectron spectroscopy

摘要

Copper clusters, deposited by evaporation onto highly oriented pyrolytic graphite (HOPG) and Dow Cyclotene, a low permittivity polymer, have been found to coalesce through surface diffusion at room temperature. We study this process by x-ray photoelectron spectroscopy under ultrahigh vacuum conditions, where cluster growth was measured through photoelectron emission intensity changes. Using a simple model, the coalescence (as opposed to diffusion) coefficients were determined for both untreated and Ar~(+)-treated substrates. It was found that Ar~(+) treatment results in reductions in both coalescence coefficient and cluster size due to increased cluster/surface interaction. The atypical coalescence behavior of Cu on untreated HOPG is shown to be due to an absence of interfacial interaction.