Growth of Au nanostructures by annealing electron beam evaporated thin films

This paper reports the synthesis of Au nanoparticles (NPs) of different sizes on fused quartz substrates by e-beam evaporation followed by thermal annealing. UV-visible absorption measurements and atomic force microscopy (AFM) studies have been carried out on the as-deposited and the annealed samples. While as-deposited samples show no signature of NP formation, the annealed samples show a signature of surface plasmon resonant (SPR) absorption at similar to 520 nm, which clearly indicates the presence of Au NPs. AFM images show the formation of Au NPs in the case of annealed samples. The red and blue shifts in the SPR peak position in the absorption spectra with increased annealing temperatures are due to the growth and the dissolution of Au NPs, respectively. The average size (diameter) of the Au NPs, estimated from the AFM data is in good agreement with the absorption results. We have observed growth in the size of the Au NPs up to a certain annealing temperature beyond which dissolution of the Au NPs starts. The formation of gold nanorings has also been observed under appropriate annealing conditions.