Effects of heat treatment on Ag particle growth and optical properties in Ag/SiO2 glass composite thin films

Abstract

Small Ag particles were embedded in SiO2 glass thin films by a multi-target sputtering method. The mean diameter of Ag particles in the as-deposited film with 28.0 at. % of Ag was estimated to be 4.4 nm and it was increased to 24.0 nm when the film was heat-treated at 700 °C for 3 h. The diameter was proportional to the cube root of the heat-treatment time, suggesting that the Ag particles grew in the supersaturated solid solution. In the optical absorption spectra of the heat-treated films, the absorption peak due to the surface plasmon resonance of Ag particles was observed about 410 nm. The peak intensity became large and the full width at half maximum of the absorption band was decreased with increasing the diameter of Ag particles.