Characterization of CoO-Doped SiO₂ Nanocomposite Films and Their Optical Transmittance Change by Nitrogen Oxide

Abstract

We developed CoO-doped nanocomposite films which change their optical transmittance by nitrogen oxide using co-sputtering method. Films sputtered from SiO 2 target with CoO pellets on at 100W under 0.27 Pa Ar atmosphere showed reversible transmittance change by NO at 350°C in the wavelength range from 400 to 800 nm. Cobalt oxide dots 4-8 nm in diameter were observed in the CoO/SiO 2 nanocomposite films by TEM observation. The heat-treated CoO/SiO 2 film at 600°C which showed no transmittance change by NO still had cobalt oxide nanoparticles embedded in SiO 2 matrix. The sensing properties is considered to be originated from nanostructure composed of functional nanoparticles which change their optical transmittance, nanopores which give paths of gas molecules and transparent matrix,