Cu related doublets green band emission in ZnO:Cu thin films

Cu-doped ZnO (ZnO:Cu) thin films were grown on Si (111) substrate by low-pressure metal-organic chemical vapor deposition equipment. The crystal structures and optical properties of as-grown sample were examined. X-ray diffraction patterns indicated a lattice relaxation after the Cu doping. The incorporation of Cu atoms into ZnO film and its existence in a bivalent state were demonstrated by x-ray photoelectron spectroscopy measurements. Low-temperature photoluminescence was carried out at temperature of 11.4 K for both unintentionally doped and Cu-doped ZnO films. A characteristic green-luminescence with fine structure consisted of doublets emission peak was observed, which was believed to be associated with Cu doping. A theoretical model based on hydrogen analog has been proposed to explain this phenomenon. It provides new information about the detailed role of Cu in ZnO thin films. (C) 2010 American Institute of Physics. [doi:10.1063/1.3516459]