Optical and microstructural characterization of nanocrystalline Cu doped ZnO diluted magnetic semiconductor thin film for optoelectronic applications

A series of Zn1-xCuxO nanocrystalline films were deposited on a silica substrate using e-beam evaporation technology. The physical properties of the deposited film were closely examined using x-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). The deposited film's structure revealed the formation of a hexagonal wurtzite structure, with no extra phases found. According to AFM analysis, the deposited Zn1-xCuxO (x = 0.0, 0.04, 0.08, 0.12, 0.16, and 0.2) film has nanocrystalline characteristics. The present findings show that increasing Cu content up to x <= 0.2 reduces the direct optical energy gap Eg from 3.286 eV (x = 0) to 2.934 eV (x = 0.2), which can be attributed to the sp-d exchange coupling. The refractive index dispersion extracted from SE analysis for Cu-doped ZnO thin films increased as the Cu dopant increased. In addition, the refractive index dispersion of the deposited film was studied using a single oscillator model proposed by Wemple-DiDomenico (WDD). It was found that the oscillator energy Eo decreases as the Cu concentration increases, while the dispersion energy Ed increases. As a result of the improvement in the optical energy band gap and the tunability of the values of the dispersive oscillator parameters Eo, Ed, n0, epsilon 0, M-1, and M-3 with increasing Cu doping levels, Cu doped ZnO films are a good candidate for optoelectronic device applications.

Automated summary

A series of Zn1-xCuxO nanocrystalline films were deposited on a silica substrate using e-beam evaporation technology, where Cu doping was found to improve the optical energy band gap and other optical properties of the films. The research findings suggest that Cu doped ZnO films have great potential for optoelectronic device applications due to the tunability of various optical parameters with increasing Cu doping levels.