Effect of Precursor Solvents on the Optical Properties of Copper Oxide Thin Films Deposited Using Spray Pyrolysis for Optoelectronic Applications

Copper oxide thin films were deposited on Pyrex glass substrates by spray pyrolysis using ethanol and distilled water (DW) respectively as solvents. Rutherford backscattering spectroscopy results indicated that films from aqueous are thicker than those of alcoholic solutions. Rutherford backscattering spectroscopic compositional results showed the films to be mainly CuO. Optical transmittance measurement of the films was analyzed to obtain the band gap, Urbach energy, optical conductivity, refractive index and the extinction coefficient which were found to be dependent on the solvent used and strongly influenced by the photon energy. The use of Tauc’s equation for calculating the bandgap indicated possible direct and indirect optical transitions. The refractive index of the films which showed normal dispersion behavior were also analyzed using single oscillator model to determine the dispersion parameters such as the dispersion energy, average oscillator strength and wavelength, zero and high frequency dielectric constant, zero frequency refractive index, optical charge carrier density, mobility and resistivity. All the determined values are higher for ethanol than aqueous samples.