Characterization of Amorphous SnO<sub>2</sub>:N Thin-films Prepared by RF Magnetron Sputtering in Ar/N<sub>2</sub> Mixed Gas Atmosphere

Nitrogen (N) has attracted attention as a hole dopant for SnOx semiconductors. We have previously reported p-type conversion of n-type SnO2 thin films by N doping by thermal annealing in N2 atmosphere. Since the diffusion length of N is several 10 nm order, uniform N doping in the film is limited in terms of practical applications. In this study, we investigated N doping into the bulk using RF magnetron sputtering in Ar/N2 mixed gas atmosphere. N-doped SnO2 (SnO2:N) thin film was fabricated by the sputtering at a substrate temperature of 300°C and a N2 concentration varied between 25 and 80%. The fabricated thin films were amorphous under all deposition conditions. As the N2 concentration increased, the absorption edge shifted to the longer wavelength and optical bandgap became narrower. XPS and PL analyses showed that as oxygen vacancy decreased, Sn-N bonding and N3- component, which acts as an acceptor, increased. Hall-effect measurement showed the SnO2:N deposited at 80% N2 concentration has p-type conduction. We believe that this is because increase in density of states of N 2p orbital. However, the mobility was 0.12 cm2/Vs, suggesting limitation in improvement of electrical properties even in N doping into the bulk.