NiO is a promising material for photovoltaics and high‐power electronics, especially as a p‐type material. However, the temperature limit of this material has not been thoroughly investigated. This work evaluates the structural evolution and thermal stability of NiO films using in situ high‐temperature X‐ray diffraction from 30°C to 1100°C in air. The film transformed from an amorphous state to a cubic NiO phase between 300°C and 400°C. The NiO (111) peak intensity follows a similar temperature‐dependent trend as the film's resistivity, indicating that higher temperatures promote increased crystallinity, which correlates with higher resistivity. At 1100°C, the formation of Ni 2 O 3 was observed, accompanied by a transition to a highly resistive film. The study presents a clear evolution of NiO film quality and crystallinity across temperatures and establishes their correlation with the material's resistive behavior.
Ellis et al. (Fri,) studied this question.