Structures and Optical Properties of TiO2 Thin Films Deposited on Unheated Substrate by DC Reactive Magnetron Sputtering

Abstract

Titanium dioxide thin films (TiO₂) were deposited on unheated substrate on a glass slide and Si-wafer by the DC reactive magnetron sputtering method at different total pressures. The crystal structure, surface morphology and optical transmittance were characterized by X-ray diffractometer, atomic force microscopy and UV-VIS-NIR spectrophotometer, respectively. The deposited films were transparent and the thickness was about 133-168 nm. XRD results showed that all samples possessed a polycrystalline structure and changed from the mixed phase of anatase and rutile, to rutile phases, as the total pressure decreased. An increase in the film’s roughness was observed with increasing sputtering pressure. The optical transmission measurements revealed that the mixed phases of anatase and rutile had higher transmittance than the pure rutile phase. The refractive index, in the visible spectrum was relatively high, while the energy band gap was found to be 3.25 eV.