Physical Properties of ZnO Thin Films Codoped with Titanium and Hydrogen Prepared by RF Magnetron Sputtering with Different Substrate Temperatures

Abstract

Transparent conducting titanium-doped zinc oxide (TZO) thin films were prepared on glass substrates by RF magnetron sputtering using 1.5 wt% TiO2-doped ZnO as the target. Electrical, structural, and optical properties of films were investigated as a function of H2/(Ar + H2) flow ratios (RH) and substrate temperatures (TS). The optimalRHvalue for achieving high conducting TZO:H thin film decreased from 10% to 1% whenTSincreased from RT to 300°C. The lowest resistivity of9.2×10-4 Ω-cm was obtained asTS=100°C andRH=7.5%. X-ray diffraction patterns showed that all of TZO:H films had a hexagonal wurtzite structure with a preferred orientation in the (002) direction. Atomic force microscopy analysis revealed that the film surface roughness increased with increasingRH. The average visible transmittance decreased with increasingRHfor the RT-deposited film, while it had not considerably changed with differentRHfor the 300°C-deposited films. The optical bandgap increased asRHincreased, which is consistent with the Burstein-Moss effect. The figure of merits indicated thatTS=100°C andRH=7.5% were optimal conditions for TZO thin films as transparent conducting electrode applications.