Structural, Optical and Electronic Properties of Cu-Doped ZnO Films Synthesized by RF Magnetron Sputtering

Zn1-xCuxO films were prepared by radio frequency (RF) magnetron sputtering method. The wurtzite ZnO crystal can be well retained up to a Cu composition of 10% and doped Cu ions substituted into Zn sites of ZnO host lattice. All the samples show high transparency over the wavelengths from 400 to 1000 nm. The room temperature (RT) resistivity shows an increase in Mn doping samples, which indicates that the doped element is at the status of deep donor levels. The decrease in the bandgap in Cu doped ZnO films rather than in pure ZnO film indicates that there are impurity bands created by Cu 3d orbital or strong d-p coupling between Cu and O in our samples. In addition, photoluminescence (PL) spectra show UV emission at ~3.19 eV shifts to lower energy side with Cu doping, indicating the possibility of band-gap engineering in Zn1-xCuxO films.