Deep-level characterization of N-doped ZnO films prepared by reactive magnetron sputtering

We report on band gap states in N-doped ZnO (ZnO:N) films that were deposited on indium tin oxide/quartz substrates by reactive magnetron sputtering. Colored ZnO:N samples showed enhanced polycrystalline with increasing N-doping concentration, as determined by x-ray diffraction patterns. Deep-level optical spectroscopy measurements revealed three characteristic deep levels located at similar to 0.98, similar to 1.20, and similar to 2.21 eV below the conduction band. In particular, the pronounced 2.21 eV band is newly introduced by the N doping and behaves as part of the valence band, resulting in band gap narrowing of ZnO. Therefore, this deep level is probably one origin of visible-light sensitivity in ZnO:N. (c) 2005 Americian Institute of Physics.