Optical properties of silicon semiconductor-supported gold nanoparticles obtained by sputtering

Gold nanoclusters are deposited directly on silicon by sputtering of a target of metallic gold using an argon plasma to provide a semiconductor-based plasmonic platform. The effects of annealing and substrate temperatures during the nanoparticles deposition and of the silicon surface energy on the shape of the nanoparticles and resulting surface plasmon resonance are investigated. The Au nanoparticles are characterized optically, structurally and morphologically using spectroscopic ellipsometry, transmission electron microscopy and atomic force microscopy to establish a correlation among the Au/Si interface reactivity, the Au nanoparticles shape and plasmonic resonance properties. It is found that post-growth annealing up to 600 degrees C of nanoparticles deposited at 60 degrees C causes aggregation of nanoparticles. Increasing the temperature of the substrate during the sputtering of gold on Si yields pancake-like nanoparticles with a large Si/Au interface reactivity forming a gold-silicides interface layer. The O2 plasma treatment of the Si surface forming a thin intentional SiO2 interface layer prevents the Au/Si interdiffusion yielding polyedrical nanoparticles whose plasmon resonance can be shifted down to 1.5 eV.