Microstructure and Optical Properties of Tantalum Modified TiO2 Thin Films Prepared by the Sol-Gel Process

Tantalum doped TiO2 thin films ((TiO2)(1-x) (Ta2O5)(x), x = 0, 0.1%, 0.3%, 0.5%, 0.8%) were prepared on ITO-coated substrates by means of the sol gel method and spin coating technology followed by rapid thermal annealing treatment (RTA). The effects of various processing parameters, including Ta content (x = 0-0.8%) and annealing temperature, on the growth and properties of thin films were investigated. Structural characteristics by X-ray diffraction analysis indicated that the doping of Ta2O5 in the TiO2 without change the anatase structure of TiO2 thin films. The optical transmittance of (TiO2)(1-x) (Ta2O5) thin films decrease from 50% down to 20% with increasing the Ta2O5 concentrations from x = 0.00 to x = 0.8%. The absorption coefficient shows energy gap were decreased with increasing Ta2O5 content from 2.932 eV for x = 0.00 to 2.717 eV for x = 0.8%. Doping TiO2 with Ta2O5 can lower its band gap and shift its optical response to the visible region.