Figure 2 shows secondary ion spectrometry SIMS profiles of N and O atoms in the ZnO:N samples after oxidative annealing at different temperatures. Here, the film thickness of the ZnO:N samples is about 0.6 m. The N-doping concentration to a depth of 0.45 m is confirmed to be about 21018 cm−3 and to be uniform for all the ZnO:N samples,regardless of oxidation temperature. On the other hand, the O concentration depends strongly on the oxidation temperature;the O concentration increases significantly by the oxidative annealing at 700 and 800 °C in view of the ZnO stoichiometry. This experimental result indicates that the oxidation state of the ZnO:N films is significantly enhanced by the high-temperature oxidation at temperatures between 700 and 800 °C, which is probably associated with a decrease in VO concentration in the ZnO:N films.