Conductive and transparent V-doped ZnO thin films grown by radio frequency magnetron sputtering

Transparent conductive films of vanadium (V)-doped zinc oxide (VZO) were deposited by radio frequency magnetron sputtering on quartz substrates using a ceramic ZnO target with V chips. The electric, optical and structural properties of VZO thin films (V concentration of 0-4 at.%) were investigated at various substrate temperatures (TSUB) from 200 to 600 °C. The resistivity sharply decreased by V doping, and the resistivity reached a minimum of about 5 × 10− 4 Ωcm and 1 × 10− 3 Ωcm for TSUB = 200 °C and 600 °C, respectively. It was almost constant up to V concentration of 1.0-1.5% and gradually increased at higher V concentration. The optical transmittance (λ = 500 nm) of VZO films (V = 0.9-1.1%) drastically degraded from about 80% to 40% for TSUB of below 225 °C while that of ZnO films was over 83% for TSUB of over 200 °C. From the dependence of growth rate and the expansion of c-axis lattice constant in the VZO film, the V configuration was considered to have a charge number of 3.