Study of optical, morphological, structural, and chemical properties of CdO thin films synthesized by thermal annealing transformation of CdCO3 thin films

Abstract

Considering the potential applications of cadmium oxide (CdO) thin films in optoelectronics, this work aims to investigate the structural, optical, compositional, and morphological properties of CdO thin films obtained by converting CdCO3 thin films into CdO by thermal annealing. The established method consists of thermal treatment for 2 h at different temperatures for CdO thin film obtention. The CdO thin films were characterized by ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetry (TGA). The direct band gap of the CdO thin films obtained was 2.39 and 2.43 eV. These values are in the range reported in the literature for CdO thin films and are related to direct transitions of electrons between valence and conduction bands. Furthermore, the HR-TEM and XRD analysis confirmed a cubic crystalline structure for CdO thin films. The low-resolution and high-resolution XPS spectra further confirm the expected chemical composition of CdO thin films.