Structural, optical and electrical investigations on Nb doped TiO2 radio-frequency sputtered thin films from a powder target

Pure and Nb doped TiO2 (TNO) thin films were deposited onto glass substrates by RF magnetron sputtering technique using a Nb and TiO2 mixture powder target at room temperature to explore the possibility of producing sputtered TNO films by a low cost process. The effect of Nb doping on the structure, morphology, optical and electrical properties of the prepared films was studied by systematically varying the Nb content from 2 to 6 wt%. GXRD results show that the deposited films mainly possess rutile phase with the (110) orientation. Raman spectra confirm that the deposited films are predominantly rutile phase. Surface roughness increases with the increase of Nb doping concentration , which may be attributed to the structural changes in the film due to the incorporation of Nb into the TiO2 lattice. Optical transmittance in the visible range reaches 85 % for the undoped films then it decreases as the doping content increases. Doping by niobium resulted in a slight increase in the optical band gap energy of the films due to the Burstein–Moss effect. The resistivity measurement of TNO films reveals that the Nb doping improves the electrical conductivity of the deposited films compared to the undoped one. The best value was observed for films deposited at 4 wt% Nb.