Fractal-Stereometric Correlation of Nanoscale Spatial Patterns of GdMnO3 Thin Films Deposited by Spin Coating

Analysing the surface morphology of annealed FTO/ZnS bilayer films: stereometric, fractal, and wettability approaches

The surface micromorphology and roughening of the thermal evaporation-coated FTO/ZnS bilayer thin films annealed at 300, 400, 500, and 550 ∘ C for 1 h have been studied. AFM images of the prepared samples were analysed by the MountainsMap software, and the effects of the annealing temperature on the surface texture of the FTO/ZnS thin film's surface were investigated. Stereometric and advanced fractal analyses showed that the sample annealed at 500 ∘ C exhibited greater surface roughness and greater skewness and kurtosis. This film also has the most isotropic surface and exhibits the highest degree of heterogeneity. Also, despite the decrease in surface roughness with increasing temperature from 500 to 550 ∘ C , the fractal dimension tends to increase. The static water contact angle measurements indicate that the film annealed at 500 ∘ C exhibits higher hydrophobicity, which can be attributed to its greater topographic roughness. Our research indicates that the surface morphology of FTO/ZnS bilayer thin films is influenced by the annealing temperature. Changing factors such as roughness, fractality, and wettability parameters to help improve surface performance make the FTO/ZnS bilayer suitable for application in electronic and solar systems.

Advanced morphological characterization of DC sputtered copper thin films

In this paper, Cu thin films were successfully deposited on glass substrates using DC magnetron sputtering at varying deposition times. The deposition time was varied as 5, 9, 11 and 17[Formula: see text]min. The obtained Cu thin films were analyzed for morphology and topography using atomic force microscopy (AFM). The size of the surface structures/grains was seen to evolve with deposition time. The conventional/statistical, fractal and multifractal analyses were carried out on AFM images using existing imaging algorithms. The arithmetic roughness and interface width parameters were seen to evolve with the sputtering time. The autocorrelation and height–height correlation functions revealed that the surfaces of all the Cu thin films exhibited self-affine character, but were not mounded properties. The fractal dimensions computed using box counting and power spectral density functions revealed that larger dimensions were associated with larger surface features. The lacunarity coefficients were too small indicating that the surfaces were generally deficient in porosity and other defects. The multifractal analyses revealed that spatial roughness does not exhibit linear relationship with the deposition time. The study reveals that surface evolution and nanoscale behavior is significantly influenced by the deposition time although a linear relationship is not established.

Correlating the Nonlinear Roughening and Optical Properties of Anatase Thin Films—A Fractal Geometric Approach

The anatase phase of TiO2 is highly suitable for photocatalytic application consequently, prerequisite an unpretentious scale‐independent understanding of its roughening‐facilitated surface topography dynamics. Herein, the nonlinear roughening in anatase thin films and its correlation with the nonlinear trend of optical properties in the framework of fractal geometry are investigated. The self‐affine nature of analyzed surfaces is confirmed from the autocorrelation function. The dynamic scaling exponents indicate the existence of Kardar–Parisi–Zhang scaling in surface growth. In addition, the trend of generalized Hurst exponent and mass exponent indicates insignificant multifractal characteristics in the analyzed surfaces. Moreover, fractal analysis explains and aids to description of roughening trend from stereometric and Minkowski functionals analysis. Furthermore, the significance of fractal dimension for probing the surface roughening is validated from the principal component analysis. Consequently, variation in optical bandgap and linear refractive index are investigated in regards to the fractal dimension and root mean‐squared surface slope and regression equations are proposed for tuning of bandgap.

Investigation of deposition temperature effect on spatial patterns of MgF2 thin films

In this work, the atomic force microscopy (AFM) technique was used to characterize 3D MgF₂ thin film surfaces through advanced analysis involving morphological, fractal, multifractal, succolarity, lacunarity and surface entropy (SE) parameters, consistent with ISO 25178-2: 2012. Samples were synthesized by electron beam deposition, grown in three different temperatures. Three different temperatures of 25°C (laboratory temperature), 150 and 300°C were chosen. The temperature of 300°C is usually the highest temperature that can be deposited with the electron beam evaporation coating system. The substrates were made of glass (diameter 16 mm, thickness 3 mm), and the samples were prepared at a pressure of 5 × 10^-5  Torr. The statistical results from the AFM images indicate that topographic asperities decrease with increasing deposition temperature, showing a decrease in roughness values. Regardless of the deposition temperature, all surfaces have a self-similar behavior, presenting a very linear PSD distribution, and, according to our results, the sample deposited at 300° had the highest spatial complexity. On the other hand, surface percolation is increasing when temperature increases, indicating that its low roughness and high spatial complexity play an important role on the formation of their most percolating surface microtexture. Our results demonstrate that the lower deposition temperature promoted the formation of less discontinuous height distributions in the MgF₂ films.

Morphological and multifractal properties of Cr thin films deposited onto different substrates

In this study, the morphological properties and micro-roughness of chromium thin film prepared by thermal evaporation technique and confirmed via EDS analysis are examined on different substrates of BK7, Silicon (Si), and glass using atomic force microscope analysis (AFM). Analysis of amplitude parameters, Minkowski functionals, and films' spatial microtexture extracted from AFM analysis showed the difference between glass substrate and the other two (BK7 and Si) substrates for the growth of chromium thin films. In addition, we observed robust signatures of multifractality of the Cr thin films deposited on all substrates we studied. Moreover, we highlight that the Glass substrates displayed the strongest multifractality indicating that such samples present space filling properties distributed over more spatial scales than the samples of BK7 and Si.

Evaluating the Topological Surface Properties of Cu/Cr Thin Films Using 3D Atomic Force Microscopy Topographical Maps

In the present work, Cu/Cr thin films were deposited on substrates of a different nature (Si, Glass, Bk7, and ITO) through a thermal evaporation deposition method. Non-contact atomic force microscopy (AFM) was used to obtain 3D AFM topographical maps of the surface for the Cu/Cr samples. Various analyses were carried out to obtain crucial parameters for the characterization of the surface features. In particular, Minkowski functionals (including the normalized Minkowski volume, the Minkowski boundary, and the Minkowski connectivity) and studies of the spatial microtexture by fractal and multifractal analyses were carried out. Different roughness parameters (including arithmetical mean height, root mean square height, skewness, kurtosis, fractal dimension, Hurst coefficient, topographical entropy, and fractal lacunarity) were quantified in these analyses for the comparison of the surface morphology of the different samples. All the samples displayed non-Gaussian randomly rough surfaces, indicating the presence of multifractal features.

Special Issue: Characterizations of Three-Dimensional Surfaces at Micro/Nanoscale

Nowadays, understanding the structural properties of materials with a specific internal microstructure on all length scales is the key to discovering new products based on new technologies [...]

Fractal Analysis on Surface Topography of Thin Films: A Review

The topographies of various surfaces have been studied in many fields due to the significant influence that surfaces have on the practical performance of a given sample. A comprehensive evaluation requires the assistance of fractal analysis, which is of significant importance for modern science and technology. Due to the deep insights of fractal theory, fractal analysis on surface topographies has been widely applied and recommended. In this paper, the remarkable uprising in recent decades of fractal analysis on the surfaces of thin films, an essential domain of surface engineering, is reviewed. By summarizing the methods used to calculate fractal dimension and the deposition techniques of thin films, the results and trends of fractal analysis are associated with the microstructure, deposition parameters, etc. and this contributes profoundly to exploring the mechanism of film growth under different conditions. Choosing appropriate methods of surface characterization and calculation methods to study diverse surfaces is the main challenge of current research on thin film surface topography by using fractal theory. Prospective developing trends are proposed based on the data extraction and statistics of the published literature in this field.