Enhancement of tin-doping on the structural, electrical, and optical properties of copper oxide thin films for optoelectronic applications

Abstract

This study investigates the structural, optical, and electrical properties of Sn-doped CuO thin films, which were synthesized using a simple solution-based method. X-ray diffraction (XRD) analysis confirmed that the doping of Sn did not induce phase transitions in CuO, as the films maintained the monoclinic structure. The crystallite size decreased from 90 nm for the un-doped sample to 37 nm for the film doped with 5 % Sn. Scanning electron microscopy (SEM) revealed that the Sn doping affected both the grain size and morphology, leading to a reduction in average grain size from 1.2 μm to 0.8 μm as the Sn concentration increased. Raman spectroscopy revealed that the characteristic Cu-O vibrational modes (Ag and Bg) remained consistent, indicating there were no significant changes to the crystal structure. Optical analysis showed a reduction in the bandgap of CuO films, decreasing from 4.03 eV for the undoped sample to 1.5eV for that doped with 5 wt% Sn. This reduction was accompanied by a redshift in the absorption edge, which can be attributed to the introduction of defect states and structural modifications. The electrical resistivity significantly decreased with increasing concentration of Sn, dropping from 380 Ω cm for the un-doped sample to 156 Ω cm at 5 wt% Sn. This reduction suggests that the introduction of free carriers enhances conductivity. These findings highlight the potential of Sn-doped CuO thin films for applications in optoelectronic devices, such as gas sensors and photovoltaics, by enhancing both optical and electrical properties while maintaining structural integrity.