Localized surface plasmon resonance phenomenon in Ag/Au-WO3-x nanocomposite thin films

Abstract

• Ag/Au-WO 3-x thin films prepared by radio-frequency magnetron sputtering. • The Ag/Au-WO 3-x films demonstrate localized surface plasmon resonance (LSPR) phenomenon. • Blueshift of the LSPR band in Ag-WO 3-x film. The localized surface plasmon resonance was investigated in composite thin films based on amorphous sub-stoichiometric tungsten oxide (WO 3-x ) matrix and noble metal nanoparticles, such as silver (Ag), gold (Au), and their alloy (Ag/Au). The films were prepared by radio-frequency magnetron sputtering of a combined target consisting of lemon-colored tungsten trioxide powder and Ag and/or Au pellets. It was found that the mean size of nanoparticles for all composite thin films according to the results of transmission electron microscopy is less than 5 nm. The obtained films demonstrate tunable plasmon absorption band. The position of the localized surface plasmon resonance peak was experimentally observed at 435, 494, and 582 nm for Ag-WO 3-x , Ag/Au-WO 3-x and Au-WO 3-x composite thin films, respectively. Blueshift of the localized surface plasmon resonance band in contrast with the results of Mie calculations for Ag-WO 3-x film was explained by possible formation of oxide shell on the surface of Ag nanoparticles.