Multi-Layered Sol–Gel Spin-Coated CuO Nanofilm Characteristic Enhancement by Sn Doping Concentration

Abstract

CuO films, with their many features, attract special attention for applications in various optoelectronics. In their pristine form, CuO films suffer from low conductivity, which limits their application. Modification, especially by doping, is thus needed. The effects of tin (Sn) doping on the structure, morphology, and optical and, more importantly, electrical properties of multi-layered copper oxide (CuO) films deposited onto tin-doped indium oxide (ITO)/glass substrates by sol–gel spin coating are examined here. The multi-layered films were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), electronic absorption (UV-Visible) spectra, and four probe methods. The results confirmed the substitution of Cu2+ ions by Sn4+ ions in the CuO crystallites without altering their monoclinic structure. The measured crystallite size values decreased with increased doping concentration, indicating increased imperfection. This applies to both 5- and 10-layered CuO films. The doping concentration affected other film characteristics, namely, surface morphology and electrical conductivity, in each layered film. Among various systems, the 10-layered film, with 1.5 at% Sn, exhibited optimal properties in terms of higher uniformity (mean square root surface roughness 41 nm) and higher conductivity (50.3 × 10−3·Ω−1·cm−1).