Photoluminescence and Raman studies of electrochemically as-grown and annealed ZnO films

The photoluminescence (PL) properties of ZnO films fabricated by electrodeposition were investigated by using annealing treatment at various temperatures and in different atmospheres. The PL spectra are composed of a dominant UV emission and a weak green emission at room temperature. Our experimental reveals that the optimum annealing condition for UV emission exists at 400 °C in N2 atmosphere. A correlation between the UV PL intensity and Raman scattering intensity is first observed below 500 °C both in N2 and O2 atmosphere under resonant excitation. We suggest the 575 cm−1 Raman peak is strongly affected by a non-radiative center, and the intense UV emission of ZnO annealed at 400 °C in N2 atmosphere is due to the reduction of this center. Two different green emission bands are observed, which show different dependences of the PL intensity on the annealing temperature. According to the defect levels in the ZnO films and the analysis of the intensity dependences on annealing temperature and atmospheres, we suggest they are caused by interstitial oxygen (Oi) and antisite oxygen (OZn), respectively.