Abstract
Crystalline and non-crystalline nickel oxide (NiO) thin films were obtained by spray pyrolysis technique (SPT) using nickel acetate tetrahydrate solutions onto glass substrates at different temperatures from 225 to 350℃. Structure of the as-deposited NiO thin films have been examined by X-ray diffraction (XRD) and atomic force microscope (AFM). The results showed that an amorphous structure of the films at low substrate temperature (Ts = 225℃), while at higher Ts ≥ 275℃, a cubic single phase structure of NiO film is formed. The refractive index (n) and the extinction coefficient (k) have been calculated from the corrected transmittance and reflectance measurements over the spectral range from 250 to 2400 nm. Some of the optical absorption parameters, such as optical dispersion energies, Eo and Ed, dielectric constant, ε, the average values of oscillator strength, So, wavelength of single oscillator λo and plasma frequency, ωp, have been evaluated.
Highlights
The optical properties of thin films are very important for many applications, including interference devices, such as antireflection coatings, laser mirrors and monochromatic filters, as well as optoelectronics, integrated optics, solar power engineering, microelectronics and optical sensor technology depending on the reflectance and transmittance properties of the films during their preparation
This paper reports the influence of substrate temperature (Ts) as an important parameter on the preparation of nickel oxide (NiO) thin films by spray pyrolysis tech
It was found that the film thickness decreases with increasing the substrate temperature despite the fact that, the kinetics of the NiO forming reaction should increase with temperature
Summary
The optical properties of thin films are very important for many applications, including interference devices, such as antireflection coatings, laser mirrors and monochromatic filters, as well as optoelectronics, integrated optics, solar power engineering, microelectronics and optical sensor technology depending on the reflectance and transmittance properties of the films during their preparation. Transition metal oxides like nickel oxides have found wide applications due to these anti-ferromagnetic semiconductor with wide gab ≈ 3.6 eV and cubic rock saltlike crystal structure [1,2] It offers promising candidature for many application such as electrocatalysis [3], positive electrode in batteries [4], fuel cell [5], electrochromic devices [6], solar thermal absorber [7], catalyst for oxygen evolution [8] and photo electrolysis [9]. Several physical and chemical methods, such as sputtering [10], pulsed laser deposition [11], chemical bath deposition [10,12] and sol-gel [13] have been used to obtain nickel oxide films All these methods offer different advantages depending on the application of interest and many efforts have been conduced to obtain films with the desirable physical and/or chemical properties. The optical absorption parameters, such as optical dispersion energies, Eo, and Ed, dielectric constant, ε, the average values of oscillator strength So, wavelength of single oscillator λo, and plasma frequency, ωp, have been evaluated under the effect of substrate temperature
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