Preparation of Gold Nanoparticles on Silica Substrate by Radio Frequency Sputtering

Radio frequency sputtering of gold on amorphous silica substrates was used for the preparation of Au nanoparticles on SiO₂. Deposition experiments were carried out in Ar plasmas under mild conditions (RF power = 5÷10 W, total pressure = 0.38 mbar, substrate temperature ≤210 °C), focusing in particular on the effect of sputtering time (5÷30 min) and substrate temperature on gold nucleation and coalescence, with the aim of obtaining SiO₂-supported Au nanoparticles characterized by precise structural and morphological features. To this aim, several analytical techniques were employed for a thorough characterization of the systems properties, including glancing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and UV-Vis absorption spectroscopy. In particular, the evolution of optical spectra, i. e., of the surface plasmon resonance peak, was used as a probe for the structural features and was related to the results obtained by other characterization techniques. Gold nanoclusters ( ∅  4÷10 nm) dispersed uniformly on silica matrices were obtained under soft conditions, with morphology ranging from island to cluster like. The obtained results make possible a careful modulation of substrate coverage and gold nanoparticle size.