Optical dispersion characterization of NiO thin films prepared by nebulized spray technique

Nickel oxide (NiO) thin films were prepared by nebulized spray pyrolysis (NSP) technique. The films are having more uniform thickness and there is no pinhole. Nickel oxide thin films have been deposited using 0.3M aqueous solution of nickel chloride NiCl2.6H2O onto microscopic glass substrates, which were chemically and ultrasonically cleaned before coating. The film depositions are carried out at various substrate temperatures from 350 to 450 o C in 50 o C step.The optical properties of the NiO films were studied using UVVis-NIR spectrometer. It is found that increase in the substrate temperature the transmittance decreases, consequently the band-gap energy wanes from 3.54eV to 3.37eV. The refractive index and the extinction coefficient have been calculated from the optical measurements. The dispersion of the refractive index is discussed in terms of the Wemple-DiDomenico single-oscillator model. The oscillator parameters such as optical dispersion energies, dielectric constant, the average value of oscillator strength, wavelength of single oscillator and plasma frequency have been evaluated.