Multifractal analysis of sputtered CaF2thin films

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

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.

The effect of dental LED light-curing unit photoactivation mode on 3D surface morphology of dental nanocomposites evaluated by two-dimensional multifractal detrended fluctuation analysis

The objective of this study was to evaluate the effect of two photoactivation modes of dental LED light-curing unit (LCUs) (conventional and "Soft Start" mode) on surface texture parameters of two dental resin-based nanocomposites. LED LCUs were considered as standard light-curing devices in contemporary dental practice. Atomic force microscopy (AFM) was applied to investigate surface morphology on 90 × 90 μm² scanning area through 2D multifractal detrended fluctuation analysis with computational algorithms basis. In order to compare 3D surface roughness at nanometer scale, singularity spectrum f[α] was used which characterize local scale properties of multifractal nature of samples. The results confirmed that larger spectrum width Δα (Δα = α_max - α_min ) of f(α) is associated with non-uniform surface morphology. Moreover, materials whose polymerization was photoactivated by the "soft start" polymerization mode, showed better quality of the surface microstructure with lower values of AFM surface texture parameters.

Fractal and multifractal characteristics of swift heavy ion induced self-affine nanostructured BaF2 thin film surfaces

Fractal and multifractal characteristics of self-affine surfaces of BaF2 thin films, deposited on crystalline Si ⟨1 1 1⟩ substrate at room temperature, were studied. Self-affine surfaces were prepared by irradiation of 120 MeV Ag(9+) ions which modified the surface morphology at nanometer scale. The surface morphology of virgin thin film and those irradiated with different ion fluences are characterized by atomic force microscopy technique. The surface roughness (interface width) shows monotonic decrease with ion fluences, while the other parameters, such as lateral correlation length, roughness exponent, and fractal dimension, did not show either monotonic decrease or increase in nature. The self-affine nature of the films is further confirmed by autocorrelation function. The power spectral density of thin films surfaces exhibits inverse power law variation with spatial frequency, suggesting the existence of fractal component in surface morphology. The multifractal detrended fluctuation analysis based on the partition function approach is also performed on virgin and irradiated thin films. It is found that the partition function exhibits the power law behavior with the segment size. Moreover, it is also seen that the scaling exponents vary nonlinearly with the moment, thereby exhibiting the multifractal nature.