The effect of synthesis temperature and time on the structural and optical properties of CuO thin films growth by hydrothermal method

In this study, CuO thin films were deposited on fluorine doped tin oxide (FTO) substrates at different synthesis time and temperature by hydrothermal method. The influences of synthesis time and temperature on the structural and optical properties of the films were investigated, via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), and optical absorption measurements. XRD results showed that all films were polycrystalline nature with monoclinic structure and the crystallinity was improved with increasing synthesis time and temperature. SEM images revealed existence of the islands, which were formed agglomeration of number of urchin like spherical structures, on the surface of the films. It was also seen from the images that amount of agglomeration increased with increasing synthesis time and temperature. EDAX measurements indicated the presence of Cu and O elements in all the films. Cu / O ratio was also calculated and found to be in the range of 1,18-0,93 from the obtained EDAX spectra. The minor peaks of Sn which was seen all the EDAX spectra were due to the FTO substrates. Room temperature optical absorption studies showed that all the films have direct transitions with band gap energies between 1,30-1,50 eV. Although increasing synthesis time caused to decrease band gap energy, increasing synthesis temperature did not cause a significant change.