Optical properties and current conduction in annealed (Ta2O5)0.94 - (TiO2)0.06 thin films

By sputtering the mosaic assembly of tantalum (Ta) and titanium (Ti) metal targets in the oxygen environment, (Ta2O5)(1-x)-(TiO2)(x), x = 0.06, thin films were deposited onto the quartz, and P/ boron-silicon (1 0 0) substrates, at room temperature (RT). The RT deposited films were annealed for 1.5 h, from 500 to 800 degrees C. Formation of the crystal structure in the films was observed at and above 700 degrees C annealing. Optical transmittance data, measured with the UV-Vis spectrophotometer, were used to find out the extinction coefficient (k), refractive index (n(opt)), and optical bandgap (E-g ) of the prepared films. With the increasing annealing temperature, both the n(opt) and E-g values were observed, decreasing from 2.218 to 2.160, and 4.23 to 4.02 eV, respectively. The extinction coefficient of amorphous films was observed lesser than the crystalline films. The current-voltage characteristics of the prepared film assisted metal-oxide-semiconductor (MOS) structures manifest different conductions, viz., ohmic at the lower electric fields; and Schottky, Poole-Frenkel, Fowler-Nordheim tunneling and space-charge-limited current, in the intermediate to higher fields, for different annealing treatments.