Effect of annealing on the properties of N-doped ZnO films deposited by RF magnetron sputtering

N-doped ZnO films were deposited by RF magnetron sputtering in N2/Ar gas mixture and were post-annealed at different temperatures (Ta) ranging from 400 to 800 °C in O2 gas at atmospheric pressure. The as-deposited and post-annealed films were characterized by their structural (XRD), compositional (SIMS, XPS), optical (UV–vis–NIR spectrometry), electrical (Hall measurements), and optoelectronic properties (PL spectra). The XRD results authenticate the improvement of crystallinity following post-annealing. The weak intensity of the (0 0 2) reflection obtained for the as-deposited N-doped ZnO films was increased with the increasing Ta to become the preferred orientation at higher Ta (800 °C). The amount of N-concentration and the chemical states of N element in ZnO films were changed with the Ta, especially above 400 °C. The average visible transmittance (400–800 nm) of the as-deposited films (26%) was increased with the increasing Ta to reach a maximum of 75% at 600 °C but then decreased. In the PL spectra, A0X emission at 3.321 eV was observed for Ta = 400 °C besides the main D0X emission. The intensity of the A0X emission was decreased with the increasing Ta whereas D0X emission became sharper and more optical emission centers were observed when Ta is increased above 400 °C.