Investigation of some physical properties of cobalt oxide films produced by spray pyrolysis technique

In this study, Co3O4 semiconductor films have been deposited onto glass substrates by spray pyrolysis method. Films have been produced at different substrate temperatures that ranging from 300 °C to 450 °C in 50 °C steps. Effect of substrate temperatures on the deposited films have been examinated via studying structural, optical and electirical properties of the films. The thicknesses of the Co3O4 samples have been determined to be about 600 nm by ellipsometer measurements. X-ray diffraction spectra have revealed that the samples were polycrystalline with face-centered cubic phase. Lattice constant and crystallite size of the films were calculated by means of x-ray diffraction spectra. The crystallite size of the samples was estimated to be 55, 56, and 54 nm at 300 °C, 350 °C and 400 °C substrate temperatures, respectively. Surface morphology was investigated using field emission scanning electron microscopy (FESEM). The optical band gap values of the films were evaluated from the absorbance measurements in the wavelength range 190–3300 nm. Co3O4 samples have direct band gap with the band gap values varying between Eopt1=1.77-2.13 eV and Eopt2=1.41-1.48 eV. The type of the electrical conductivity of the films has been determined to be p-type characteristic using hot probe method. The electrical properties of the samples having planar structures have been measured in dark at room temperature by applying the voltage values between 0.01 and 100 V.