Preparation of TiO2-doped ZnO films by radio frequency magnetron sputtering in ambient hydrogen–argon gas

Highly conductive, transparent TiO2-doped ZnO films are grown by radio frequency (RF) magnetron sputtering in ambient hydrogen–argon (Ar + H2) gas at a temperature of 150 °C and the effects of the Ti and H2 content on the structural, electrical, and optical properties of these TiO2-doped ZnO films are subsequently investigated. X-ray photoelectron spectroscopy examination indicates that the variation of the H2 content in Ar has an influence upon the chemical state of the films. The X-ray diffraction spectra indicate that all the samples are polycrystalline ZnO films oriented perpendicular to the substrate surface (c-axis orientation). The lowest resistivity, 6.50 × 10−4 Ω cm, is obtained with 1.28 wt.% Ti and H2 content in a 15% Ar ambient. The optical transmittance for TiO2-doped ZnO films in the visible region is about 85%. Due to the Burstein–Moss effect, the energy band gap increases with the carrier concentration.