Effect of substrate temperature on the electrically conductive stability of sputtered NiO films

Nickel oxide is a typical p-type semiconductor which has a wide range of applications due to its particular electrical, optical, and magnetic properties. However, the electrical conductivity of sputtered NiO film is unstable in the humid air and decay rapidly (electrical aging) with time. From the view point of application, trying to stabilize the electrical conductivity of NiO films is essential. In this paper, the stability of NiO films was improved by heating substrate. The result shows that the aging rate has obviously slowed down as the NiO films were deposited at the elevated temperatures of 200 °C and 300 °C. This improvement has strong relationship to the surface structure of the film. The preferred orientation of NiO film changes from (111) to (200) as the substrate temperature is increased and this change occurs progressively in NiO film from the topmost surface to the bottom material adjacent to the substrate. It is found that the electrical aging of sputtered NiO film could be depressed with forming advantageous (200) planes by elevating substrate temperature.