Effect of Substrate Temperature on Structural and Optical Properties of Au/SiO2 Nanocomposite Films Prepared by RF Magnetron Sputtering

Abstract

Silica films containing gold nanoparticles were grown by magnetron radio frequency (rf) sputtering technique under various deposition conditions. The structural and optical properties of the composite films deposited at 400℃ substrate temperature were compared with those deposited at room temperature. Effect of substrate temperature of AuNPs on micro structural properties of the Au/SiO2nanocomposite films, such as size, dislocation density (δ), strain (e) and lattice distortion (LD) have been investigated. The face-centered cubic crystalline structure of Au nanoparticles inclusion in the amorphous silica dielectric matrix was confirmed using X-ray diffraction. The average grain size of AuNPs has been found in the range of 0.56 - 0.60 nm and 1.15 - 1.23 nm at 3 × 10﹣3 mbar and 2 × 10﹣3mbar argon pressure respectively. The δ, e, LD values change inversely with the increasing of the substrate temperatures. These composites exhibit the optical features of a semiconductor with direct band gap. The band gap energy of 3.85 eV and 4.1 eV achieved for gold nanoparticles when the substrate temperatures increases from 25℃ to 400℃. A peak wavelength of the surface plasmon resonance band absorption (SPR) characteristic of gold nanoparticle was found around 500 nm for the sample deposited at 2 × 10﹣3 mbar and at 400℃ substrate temperature.