Properties of heavily W-doped TiO_2 films deposited on Al_2O_3-deposited glass by simultaneous rf and dc magnetron sputtering

摘要

TiO_2 films were heavily doped with W (TiO_2:W) by simultaneous rf magnetron sputtering of TiO_2, 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 TiO_2, WO_3 and TiWO_5 in the TiO_2:W film was detected by XPS analysis. Besides, tungsten in TiO_2:W film on the bare glass may form mixed valence of W~(0+) and W~(6+). Electrical conductivity was primarily due to the contribution of oxygen vacancies and W donors (W_(Ti)). When the film thickness increased, the TiO_2:W film showed higher carrier concentration and higher mobility. Furthermore, the resistivity and the transmission decreased obviously with film thickness. On comparing with the TiO_2:W film deposited on the bare glass, the TiO_2:W film on the Al_2O_3-deposited glass exhibited lower surface roughness, lower resistivity, higher optical energy gap, higher optical transmission, and lower stress-optical coefficient.