Unique structural and mechanical properties of ultrathin au films grown ondendrimer-mediated substrates

Evidence is presented here for very significant improvements in film qualit y when Au is deposited on a self-assembled monolayer of amine-terminated po ly(amidoamine) (PAMAM) dendrimers (generation G8) on SiOx. In addition, the nanomechanical response of the monolayer dendrimer film itself and the Au/ dendrimer bilayer configuration is reported for the first time. Ultrathin ( 12.5 nm) Au grown on the native oxide of Si(100) results in an apparently c ontinuous but poorly adherent film with vertical RMS roughness, approximate to1 nm, and occasional, very much larger scale (approximate to 75 nm) feat ures. Dendrimer-mediated Au films have substantially reduced roughness (app roximate to0.4 nm) and no large-scale features. Nanoindentation studies dem onstrate surprisingly large differences in the mechanical responses of Au f ilms with and without a dendrimer interlayer. The nanoindentation hardness (a measure of resistance to plastic deformation) of the dendrimer-mediated 12.5-nm Au film is significantly higher than that of the 12.5-nm Au layer a lone. This mechanical strengthening is attributed to the compressed and con fined nature of the dendrimer interlayer and points to the possibility of u sing hybrid organic/inorganic nanocomposites as tribomaterials.