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 (R H) and substrate temperatures (T S). The optimal R H value for achieving high conducting TZO:H thin film decreased from 10% to 1% when T S increased from RT to 300°C. The lowest resistivity of 9.2 × 10 - 4 Ω-cm was obtained as T S = 100 °C and R H = 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 increasing R H. The average visible transmittance decreased with increasing R H for the RT-deposited film, while it had not considerably changed with different R H for the 300°C-deposited films. The optical bandgap increased as R H increased, which is consistent with the Burstein-Moss effect. The figure of merits indicated that T S = 100 °C and R H = 7.5 % were optimal conditions for TZO thin films as transparent conducting electrode applications.