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

Tantalum doped TiO 2 thin films ((TiO 2 ) 1− x (Ta 2 O 5 ) 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 Ta 2 O 5 in the TiO 2 without change the anatase structure of TiO 2 thin films. The optical transmittance of (TiO 2 ) 1− x (Ta 2 O 5 ) x thin films decrease from 50% down to 20% with increasing the Ta 2 O 5 concentrations from x =0.00 to x =0.8%. The absorption coefficient shows energy gap were decreased with increasing Ta 2 O 5 content from 2.932 eV for x =0.00 to 2.717 eV for x =0.8%. Doping TiO 2 with Ta 2 O 5 can lower its band gap and shift its optical response to the visible region.