Surface characterization of NiO thin films deposited by RF‐magnetron sputtering at different thickness: Statistical and multifractal approach

Abstract

Fractal and multifractal are the most important processes and concepts in describing and examining surface morphology, and for this reason, these concepts are an important approach for analyzing the properties and surface geometry of thin films. In this article, multifractal analysis was performed on images, prepared using atomic force microscopy (AFM), of the surface morphology of nickel oxide thin films deposited by RF‐Magnetron sputtering at different thicknesses on the glass substrate. The effect of thickness on the surface properties of the layers was studied by applying multifractal and statistical methods on AFM images. The results obtained from the multifractal spectrum show that the surface of the nickel oxide thin films deposited at different thicknesses are multifractal. The multifractal analysis demonstrated that multifractality and complexity of the surface of nickel oxide thin films changes and decrease with thicknesses. We also used statistical parameters to better examine AFM images to study the effects of layers thickness on the deposited NiO thin films. The results indicated that the statistical parameters are a function of the layer's thickness of NiO thin films. Hence, the isotropic properties and functional parameters changed with changing surface thickness. Research Highlights Multifractal analysis was applied to the AFM images to study the surface morphology of NiO thin films. The multifractal nature of the surface of NiO thin films is observed. The layers have become more isotropic with increasing thickness. The results illustrated that deposition masses occurred more at the highest sites on the surface. Multifractality of the surface of the sample decreased with increasing layer thickness.

Influence of film thickness on structural, optical, and electrical properties of sputtered nickel oxide thin films

“…As the film thickness augments, the refractive indices show an increase. However, as the wavelength of the incoming photon increases, the indices decline, converging towards values typical of bulk and stoichiometric NiO samples (Astinchap et al, 2022). This trend aligns with the improved crystallinity observed in thicker samples.…”

“…Therefore, it is necessary to develop stable and reproducible p‐type oxide semiconductor thin films. In this regard, nickel oxide structure (with a band gap of 3.5 to 4 eV) is one of the p‐type transition metal oxides, which has attracted the attention of researchers and industries because of its excellent electronic properties and biocompatibility, and the combination of low‐cost and abundant elements (Astinchap et al, 2022; Liu et al, 2020; Napari et al, 2021; Ukoba et al, 2018). Nickel oxide films have been used in various electronic devices as p‐type transparent conductors, electrochromic materials, solar cells, and in sensors or chemical biosensors (Astinchap et al, 2022; Chen et al, 2022; Chen et al, 2021; Napari et al, 2021).…”