Structural, microstructural, optical and electrical properties of spray deposited rare-earth metal (Sm) ions doped CdO thin films

Abstract

Rare-earth metal, samarium (Sm) ions, doped cadmium oxide (CdO) thin films were deposited on microscopic glass substrates at 300 °C by a homemade spray pyrolysis experimental setup. The deposited films were characterized for their structural, microstructural, optical and electrical properties. X-ray diffraction analysis confirmed that the deposited films belong to the cubic crystal system. The undoped films show a slight preferential growth along (111) diffraction plane, and the (200) plane emerged as the preferential growth direction when the Sm-doping is higher than 0.75 wt%. Field emission scanning electron microscopy analysis reveals that the average grain size and surface morphology of CdO films are effectively modified by various Sm-doping concentration. The elemental composition of the deposited films was analyzed using energy dispersive spectroscopy. The metal oxide (Cd–O) bond vibrations were observed at 319, 389, 551,779 and 941 cm−1 by micro-Raman studies at room temperature. Oxidation state of Sm3+ was confirmed by X-ray photoelectron spectroscopy analysis. A transmittance (ranging 83–86 %) in the visible and NIR region was observed for the various Sm concentrations. The optical band gap estimated varies between 2.39 and 2.67 eV, depending on the Sm-doping concentration. The negative sign of Hall coefficient confirmed the n-type conductivity and the mobility and carrier concentration are in the 45–78 cm2/V s, and 1.0 × 1020–3.36 × 1020 cm−3 range respectively.