Annealing Temperature-Dependent Optical Properties of (Ta2O5)0.965—(TiO2)0.035 Thin Films

Tantalum (Ta) and titanium (Ti) metal targets were sputtered to deposit (Ta2O5)0.965—(TiO2)0.035 composite thin films onto the quartz and P/boron–silicon (1 0 0) substrates by direct current (DC) magnetron sputtering in the oxygen environment at room temperature (RT). The as-deposited films were followed by the annealing in the temperature range from 500 to 800 °C for 90 min. X-ray diffraction results indicated the formation of Ta2O5 structure of annealed thin films. Optical measurements were performed by UV-Vis spectrophotometer, and obtained transmittance versus wavelength plot was used to determine the refractive index (n), extinction coefficient (k), and optical energy band gap (Eg) of the film material. The optical parameters derived from transmittance (T) measurement were observed varying with annealing temperature. The refractive index of prepared (Ta2O5)0.965—(TiO2)0.035 thin films, at 550 nm, was observed decreasing from 2.21 to 2.14, and Eg from 4.27 to 3.88 eV, with increasing annealing temperature. The extinction coefficient associated with the absorbance was observed decreasing with the increasing wavelength.