Effect of annealing conditions on the structural, electrical and optical properties of Li-doped NiO thin films

Transparent conductive oxide (TCO) p-type Li-doped NiO thin films were deposited on the (0001) sapphire substrates by magnetron sputtering technique with a high purity NiO:Li2O ceramic target. We systematically investigated the structural, electrical and optical properties of NiO:Li thin films annealed in different conditions. We found that annealing in different conditions greatly affects the physical properties of NiO:Li thin films. Compared with the NiO:Li thin film annealed in oxygen, the hole concentration of NiO:Li thin film annealed in nitrogen at the same processing temperature is obviously lower. Annealed in oxygen at 500 °C, NiO:Li films show excellent crystal quality with single (111) orientation, high hole concentrations. When the annealing temperature increased, the transmittance of NiO:Li thin films become better for wavelength range from ultraviolet (UV) to visible with a significant absorption edge near 350 nm.