Effects of the annealing environment on green luminescence of ZnO thin films

Abstract

The effects on visible light emission of ZnO thin films annealed by various annealing conditions were investigated. Based on the photoluminescence (PL) properties, stronger green light emission of ZnO thin films was obtained as annealing in oxygen than in other atmospheres. The green light emission increased in intensity with the increased annealing temperature and the strongest green light emission stood at the temperature of 800 °C. According to the structural analyses, ZnO films show a preferred (0 0 2) orientation peak and the crystalline became better through annealing process. The surface morphologies became closer to the hexagonal shape and also became denser as annealing in oxygen. Mechanism analysis of PL shows that green emission band should be derived from the defects, which is greatly related to oxygen concentration during annealing, formed in ZnO films. The relationship between green luminescence and oxygen concentration in ZnO thin films was discussed.