Influence of process parameters on the morphology of Au/SiO2 nanocomposites synthesized by radio-frequency sputtering

Metal nanoparticles on oxide matrices have gained a markedly increasing consideration with regard to both scientific and applicative purposes, thanks to the possibility of tailoring the system characteristics by a proper choice of the preparation route and the processing conditions. In the present work, Au/SiO2 nanocomposites were prepared by radio-frequency (rf) sputtering of gold from Ar plasmas on amorphous silica substrates. Particular attention was devoted to the influence of the synthesis parameters on the chemicophysical properties of the final nanosystems. To this regard, both in situ and ex situ characterization techniques were adopted. In particular, laser reflection interferometry was employed for an in situ monitoring of growth processes, while ex situ analyses were specifically dedicated to the investigation of Au/SiO2 nanostructure, chemical composition, optical properties, and surface morphology (glancing-incidence x-ray diffraction, transmission electron microscopy, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, ultraviolet-visible absorption, and atomic force microscopy). The obtained results showed the possibility of tailoring the Au/SiO2 morphology from clusterlike to islandlike systems or continuous films, with consequent modification of the optical properties, by a proper choice of total pressure, rf power, deposition time, and growth temperature.