An investigation on CuO thin films grown by ultrasonic spray pyrolysis at different substrate temperatures: Structural, optical and supercapacitor electrode characterizations

Copper oxide (CuO) thin films were grown on glass substrates by performing ultrasonic spray pyrolysis (USP) method at different substrate temperatures (300 ?C, 400 ?C, 450 ?C, and 500 ?C). The prepared CuO thin films were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX), UV-visible spectroscopy, and photoluminescence (PL) spectroscopy measurements in order to assess the effects changed substrate temperature on structural, morphological, and optical properties of the grown materials. Also, the suitability of the grown films as electrodes in supercapacitor applications was investigated with respect to variable substrate temperatures. The XRD patterns revealed that the samples were polycrystalline in nature exhibiting tenorite phase of CuO structure preferential orientation along (11 1) plane and the corresponding crystallite size ranged from 28.14 nm to 67.98 nm. The SEM images displayed morphological modifications in the prepared CuO thin films as the substrate temperatures incresed. The XPS and EDX analyses confirmed the successful deposition of aimed materials on the fabricated thin films. It was also obtained that optical absorbance decreased due to the increased substrate temperatures and optical energy bandgaps changed between 1.53 eV and 1.71 eV as the substrate temperatures varied. The electrochemical supercapacitive features of the CuO nanostructures thin films were studied with the help of cyclic voltammetry (CV), galvostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS).