Effect of holmium on structural and optical properties of sol–gel spin coating-derived cadmium oxide thin films

In this work, the structural and optical characteristics of undoped and Ho-doped CdO thin films developed via the sol–gel spin coating method on a glass substrate are investigated for the first time. XRD spectra, UV–Vis spectroscopy, and photoluminescence spectra were used for analyzing the structural and spectroscopic characteristics of the films, respectively. X-ray diffraction spectra revealed the cubic structure and preferred orientation of the films, along with their polycrystalline nature. The scanning electron microscopy revealed the morphology of CdO thin films like granular and cauliflower structures. The composition of the present materials is shown in the EDX graph. Absorption spectra were used to estimate the optical band gap of CdO thin films. With a rise in Ho doping, the optical study revealed a considerable decrease in the optical bandgap energy and an increase in transmittance in the visible region. We also investigate and analyze the nonlinear optical constants. The photoluminescence spectra of CdO thin films revealed a green emission. The deposited thin films exhibited the maximum emission of white light, with color coordinates in the almost white light area.