The structural, optical and Urbach tail studies of polycrystalline CuO thin films synthesized by SILAR technique

Copper oxide (CuO) thin films were synthesized onto microscope glass substrates at 55 °C with different pH values (pH = 9.50, 10.05, and 10.50), resulting in different film thicknesses using the successive ionic layer adsorption and reaction (SILAR) technique. The film structure was characterized using the x-ray diffraction technique and scanning electron microscope (SEM). The elemental analysis was performed by energy dispersive x-ray spectroscopy (EDS). The optical properties of the films were examined using a UV–vis spectrophotometer. In all films, the XRD measurements revealed the monoclinic CuO phase. The direct optical band gap width of the film showed a red shift and decreased from 2.66 eV to 2.25 eV with increasing film thickness. Likewise, the Urbach tail width of the films dropped from 1.045 eV to 0.665 eV. Additionally, optical parameters like refractive index ($n$), extinction coefficient ($k$), real (${\epsilon }_1$) and imaginary (${\epsilon }_2$) components of dielectric constant were calculated.