Silica films containing gold nanoparticles were grown by magnetron radio frequency (rf) sputtering technique under various deposition conditions. XRD measurements revealed the formation of gold nanoparticles embedded in amorphous silica films. The structural and optical properties of the films were tailored by varying the system pressure and the sputtering area ratio of Au/SiO₂ for the target (𝑟𝐴𝑢/𝑆𝑖𝑂₂). No apparent surface plasmon resonance peak was observed for the lower area ratio. An anomalous blue shift in peak position of SPR band absorption with the increase of gold nanoparticles size is observed. The peak wavelength of the surface plasmon resonance (SPR) was found to redshift from 500 nm to 510 nm, while the size decreases from 2.5 nm to 2.10 nm and disappears for the size lower than 2 nm. This composite exhibits the optical features of a semiconductor with direct band gap. The band gap energy of 3.45 eV and 4 eV achieved for gold nanoparticles when the area ratio decreases of 2.6% to 1.6% respectively.

Keywords: Au Nanoparticles; Silica Films; Surface Plasmon Resonance; Sputtering;