Correlation between crystallographic orientations and Raman spectra of TiO2 sputtered films with changing degrees of plasma exposure

Most of the titanium dioxide (TiO2) films deposited in this study were transparent and had anatase crystal structures, while some of the films were semitransparent. The anatase phase of the as-deposited films was revealed in the Raman spectra with a Raman shift of 145 cm−1 and x-ray diffraction patterns. When the films were deposited at the working gas pressure (PW) of 3 mTorr with increasing plasma exposure, the highest intensity of the peak which had a Raman shift of 145 cm−1 steeply increased with preferential enhancement of the crystallographic orientation of the A(220) plane, where A shows the anatase phase of TiO2. However, in the films deposited at the PW of 1 mTorr with decreasing plasma exposure, such Raman peak intensity gradually decreased at the condition that the preferential crystallographic orientation changed from A(220) to A(101). This implies that the change in the Raman peak intensity may be closely related to the change in the A(220) peak intensity. When the TiO2 crystallites became la...