Effect of V doping on initial growth of ZnO film on c-face sapphire substrate

The effects of the vanadium (V) doping on the initial growth of ZnO films on a c-face sapphire substrate were investigated. The V-doped ZnO (VZO) films were grown at 200 °C by RF magnetron sputtering with various V concentration ranges. The unit cell volume of the VZO films became larger than that of the ZnO films, but the grain size of the VZO films shrank with a smooth surface. It was also found that the V doping enhanced c-axis alignment at the initial growth in the range of about 10-40 nm thick. Furthermore, it can be considered that V atoms were located at the interstitial sites in the state of V3+ from an analysis of the chemical binding states. Therefore, considering the effect of the V doping on the improvement in rotational symmetry of in-plane orientation, epitaxial alignment to the sapphire substrate was enhanced by the interstitial V incorporation.