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 N-2/Ar gas mixture and were post-annealed at different temperatures (T-a) ranging from 400 to 800 degrees C in O-2 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 T-a to become the preferred orientation at higher T-a (800 degrees C). The amount of N-concentration and the chemical states of N element in ZnO films were changed with the T-a, especially above 400 degrees C. The average visible transmittance (400-800 nm) of the as-deposited films (26%) was increased with the increasing T-a to reach a maximum of 75% at 600 degrees C but then decreased. In the PL spectra, A(0)X emission at 3.321 eV was observed for T-a = 400 degrees C besides the main (DX)-X-0 emission. The intensity of the A(0)X emission was decreased with the increasing T-a whereas (DX)-X-0 emission became sharper and more optical emission centers were observed when T-a is increased above 400 degrees C. (C) 2008 Elsevier B.V. All rights reserved.