Raman scattering, emission, and deep defect evolution in ZnO:In thin films

The impact of In doping on the parameters of ZnO films has been studied. Film structure, emission, and evolution of O- and In-related defects versus In contents have been investigated using Raman scattering, photoluminescence (PL), x-ray diffraction, and high-resolution x-ray photoelectron spectroscopy (HR-XPS). Three stages of the variation of optical and structural parameters of ZnO films at In doping were detected. The formation of In-related point defects is connected with the first two stages, which is accompanied by improving the ZnO crystal structure, the insignificant changes of Raman scattering spectra, and the intensity increases of high energy emission bands. At the third stage of In doping, the intensities of Raman peaks and PL bands decrease owing to the formation of In-related nanoclusters and O-related defects. To analyze the In-related defects, HR-XPS was monitored for the lines (i) In 3d3/2 and In3d5/2, and (ii) In4d3/2 and In4d5/2 in In-doped ZnO thin films. The trend in the change of the In ion charges versus In contents has been revealed and discussed.