Observations of nitrogen-related photoluminescence bands from nitrogen-doped ZnO films

We report the synthesis and photoluminescence (PL) properties of nitrogen-doped ZnO films. These films were synthesized by filtered cathodic vacuum arc technique; nitrogen gas was used as a dopant source. X-ray diffraction results indicated that the ZnO films were highly c-axis oriented. The appearance of the nitrogen-related local vibrational Raman scattering peaks showed that nitrogen was incorporated into the films. In the PL spectrum of the undoped films, a near band edge exciton emission peak at 384 nm and a weak visible band related to oxygen interstitial at 660 nm were observed. For nitrogen-doped films, besides the two emission bands observed in the undoped samples, two additional PL bands at around 450 and 890 nm were detected. According to the first-principle total energy calculation, nitrogen-induced acceptor energy level is located at 0.4 eV above the valence band maximum. Therefore the emission band at around 450 nm may originate from the recombination of photo-generated electrons with neutral nitrogen acceptors, and the 890 nm band is attributed to electron transition from oxygen interstitial to this neutral nitrogen acceptors. (C) 2003 Elsevier Science B.V. All rights reserved.