Effect of annealing temperature on the structural, morphological, optical and electrical properties of Co3O4 thin film by nebulizer spray pyrolysis technique

Abstract

In this investigation, spray pyrolysis using nebulizer technique is employed to fabricate cobalt oxide (Co3O4) thin films onto glass substrate at 250 A degrees C. The deposited homogeneous Co3O4 thin films were thermally treated under different annealing temperatures. The influences of annealing temperature on the properties of the coated thin films are examined by XRD, SEM, EDAX, UV-Vis-NIR spectrometer and four probe techniques. XRD analysis confirmed the growth of polycrystalline cubic Co3O4 thin films. SEM analysis showed that the size of the spherical grains is increased with the increase of annealing temperature. The EDAX spectra have indicated that the grown film is in the composition of Co and O. The optical spectra has shown a decrease in transmittance for the increase of annealing temperature, and consequently the band-gap energy values are reduced as 2.26, 2.05 and 1.73 eV for as-deposited, annealed at 300 and 400 A degrees C respectively. The optical constants like refractive index, extinction coefficient have also been determined from the optical measurements. Current versus voltage studies showed the ohmic nature of the films.