Optical properties of Au/SiO₂ nano-composite films prepared by induction-coil-coupled plasma sputtering

Au/SiO₂ nano-composite thin films with 3 to 65 vol% Au were prepared by induction-coil-coupled plasma sputtering, and the effect of heat-treatment on the nano-structure and optical property of the films were investigated. The mean diameter of the Au particles in the as-deposited films was about 8 nm and increased from 10 to 30 nm after the heat treatments at 900°C. The optical absorption was greatly improved by the heat-treatment due to the increase of Au particle sizes. At the heat-treatment of 900°C, Au/SiO₂ films containing 3 to 65 vol% Au showed absorption peaks at the wavelength of 540 to 560 nm, while no absorption peak was observed in the as-deposited films containing more than 12 vol% Au. The intensity of the absorption peak for the Au/SiO₂ films heat treated at 900°C increased with increasing Au content, showing a maximum value around the Au content of 37 vol%.