Effect of Oxygen-Evaporation-Preventative Post-Annealing Gas Conditions on NiO Thin Films

Abstract

In this study, NiO films were fabricated through radio frequency sputtering with various oxygen flow rates and processed via rapid thermal annealing under Ar, O2, and N2 atmospheres. The electrical, optical, and crystallographic properties of the NiO films were influenced by their oxygen content in each film. As the oxygen content, carrier concentration, and resistivity increased, transmittance and mobility decreased. The carrier mobility of the NiO film in the p-type layer of the photodetector requires improvement. Rapid thermal annealing (RTA) has been widely used to improve the crystallinity and mobility of films. However, the reduction in oxygen content during RTA causes a decrease in the carrier concentration and transmittance of NiO films. Regarding the aim of preventing a reduction in oxygen content in the NiO films due to the RTA process, an O2 atmosphere (compared with Ar and N2 atmospheres) was identified as the optimal condition for mobility (3.42 cm2/V center dot s) and transmittance (50%).