Enhancement of Visible Light Emission of Ni-Doped ZnO Sprayed Thin Films by Copper Co-Doping

Abstract

Abstract—This article deals with the effect of various copper (Cu) contents (1, 2, and 3 wt %) on the physical properties of sprayed nickel doped ZnO thin films (NZO) (Ni : 0.5%). The X-ray diffraction (XRD) results revealed that all samples possess a hexagonal wurtzite crystal structure with the preferential peaks oriented towards (002) direction parallel to c-axis. The morphological study also showed that co-doping aids in the enhancement of crystallinity and improves the roughness of ZnO films. In addition, the optical transmittance in the visible region ranged from 60 to 90%. As attested by the optical study, optical testing revealed that all films were extremely transparent and dependent on the dopant concentrations. The UV peak positions for NZO: Cu samples shift slightly in wavelength to the blue end in comparison with the NZO. Besides, the exchange interactions between Zn and Cu shifted the optical energy gap to the red with the addition of Cu contents. Finally, Cu doped films exhibited strong visible emission due to the modulation of the band structure and, subsequently, new levels acting as emission centers were formed in the ZnO forbidden band.