Green-emission and n-type conductivity of ZnO:Zn films obtained using vapor deposition method

ZnO:Zn films with strong adhesion to the substrate were obtained by evaporating ZnO powders in the mixture of N2 and H2. The ZnO:Zn films produced in the reductive gas showed bright green photoluminescence and n-type conductivity. After the ZnO:Zn films were re-fired in the air, the conductivity and luminescent intensity decrease to less than 1% and about 50% of the initial values, respectively. For the two different types of samples obtained in the reductive gas and in the air, respectively, their point defects showed notable difference as indicated by the measurements of electron spin resonance and X-ray photoelectron spectroscopies. The native defects account for the green-emission while the n-type conductivity is perhaps associated with the hydrogen doping.