Structural and optical properties of ZnO thin films with heavy Cu-doping prepared by magnetron co-sputtering

Cu-doping can modulate the properties of ZnO thin films. Most previous researchers studied ZnO:Cu films with moderate doping level, while this work was focused on heavy Cu-doping (13-23.8%) effect on ZnO thin films prepared by magnetron co-sputtering. The microstructure and optical properties of the films were systematically investigated. The results show that moderate Cu-doping enhances the crystal grain size of the films, whereas heavy doping reduces it. The fluorescence quenching effect, the red shift phenomenon and the band gap narrowing effect in emission and absorption characteristics resulting from Cu-doping are more significant at heavy doping level. A promising band gap reduction of 0.64 eV was achieved at 23.8% doping level.