The effect of substrate temperature on the structural, optical, and electrical properties of Cu-doped indium oxide (CIO) thin films deposited by spray pyrolysis technique

A simple low-cost spray pyrolysis deposition method was introduced to prepare Cu-doped indium oxide (CIO) thin films on a well-cleaned glass substrate by acetone followed by de-ionized water and ethyl alcohol. 0.5 molarity of In(NO3)3·xH2O (99%, Sigma Aldrich) and CuCl2 (Sigma Aldrich, 98%) were dissolved in separate beakers and then mixed by stirring for 3 h by adding ethyl glycol. The prepared solution was deposited in the form of thin films on the substrate at various temperatures ranging from 300 to 450 ∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}C with a 50 ∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}C increment. The XRD data confirm the structure of the deposited films as cubic with a significantly preferred orientation. UV–Vis spectroscopy analysis was used to calculate the optical properties. The band gap values were calculated as 2.3 eV to 3.82 eV and an optical transmission was observed at 85% in visible–NIR (near-infrared) region. Four-probe technique was utilized to find the sheet resistance, as well as electrical conductivities, and the values are found to be 3.45 ×\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document} 102 Ω/square and 3.4 S cm−1, respectively. XPS analysis was used to identify the In, Cu, and O elements in the samples. The transmission spectra were examined between the wavelength ranges from 300 nm to 1000 nm. The topology and surface morphology of CIO films were investigated by atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM).