Properties of heavily W-doped TiO2 films deposited on Al2O3-deposited glass by simultaneous rf and dc magnetron sputtering

TiO2 films were heavily doped with W (TiO2:W) by simultaneous rf magnetron sputtering of TiO2, and dc magnetron sputtering of W. The advantage of this method is that the W content could be changed in a wide range. The coexistence of TiO2, WO3 and TiWO5 in the TiO2:W film was detected by XPS analysis. Besides, tungsten in TiO2:W film on the bare glass may form mixed valence of W0+ and W6+. Electrical conductivity was primarily due to the contribution of oxygen vacancies and W donors (WTi). When the film thickness increased, the TiO2:W film showed higher carrier concentration and higher mobility. Furthermore, the resistivity and the transmission decreased obviously with film thickness. On comparing with the TiO2:W film deposited on the bare glass, the TiO2:W film on the Al2O3-deposited glass exhibited lower surface roughness, lower resistivity, higher optical energy gap, higher optical transmission, and lower stress-optical coefficient.