Transparent thin film transistors (TTFT) were fabricated using the rf magnetron sputtered ZnO-SnO2 films as active layers. A ceramic target whose Zn atomic ratio to Sn is 2:1 was employed for the deposition of ZnO-SnO2 films. To study the post-annealing effects on the properties of TTFT, ZnO-SnO2 films were annealed at 200℃ or 400℃ for 5 min before In deposition for source and drain electrodes. Oxygen was added into chamber during sputtering to raise the resistivity of ZnO-SnO2 films. The effects of oxygen addition on the properties of TTFT were also investigated. 100 nm Si3N4 film grown on 100 nm SiO2 film was used as gate dielectrics. The mobility, Ion/Ioff, interface state density etc. were obtained from the transfer characteristics of ZnO-SnO2 TTFTs.

Ga-doped ZnO-SnO2 (ZSGO) films were deposited by rf magnetron sputtering and their structural and electrical properties were investigated. In order to fabricate the target for sputtering, the mixture of ZnO, SnO2 (1:1 weight ratio) and Ga2O3 (3.0 wt%) powder was calcined at 800℃ for 1 h. The substrate temperature was varied from room temperature to 300℃. The crystallographic properties and the surface morphologies of the films were studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The optical transmittances of the films were measured and the optical energy band gaps were obtained from the absorption coefficients. The resistivity variation with substrate temperature was measured. Auger electron spectroscopy was employed to find the atomic ratio of Zn, Sn, Ga and O in the film deposited at room temperature. ZSGO films exhibited the optical transmittance in the visible region of more than 80% and resistivity higher than 10 Ωcm.