Sebastian Stach

Topographic Characterization of Cu–Ni NPs @ a-C:H Films by AFM and Multifractal Analysis

In the present work three-dimensional (3-D) surface topography of Cu-Ni nanoparticles in hydrogenated amorphous carbon (Cu-Ni NPs @ a-C:H) with constant thickness of Cu and three thicknesses of Ni prepared by RF-Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) system were investigated. The thin films of Cu-Ni NPs @ a-C:H with constant thickness of Cu and three thicknesses of Ni deposited by radio frequency (RF)-sputtering and RF-PECVD systems, were characterized. To determine the mass thickness and atomic structure of the films, the Rutherford backscattering spectroscopy (RBS) spectra was applied. The absorption spectra were applied to study localized surface plasmon resonance (LSPR) peaks of Cu-Ni NPs (observed around 608 nm in visible spectra), which is widened and shifted to lower wavelengths as the thickness of Ni over layer increases, and their changes are also evaluated by the 3-D surface topography. These nanostructures were investigated over square areas of 1 μm × 1 μm using atomic force microscopy (AFM) and multifractal analysis. Topographic characterization of surface samples (in amplitude, spatial distribution, and pattern of surface characteristics) highlighted 3-D surfaces with multifractal features which can be quantitatively estimated by the multifractal measures. The 3-D surface topography Cu-Ni NPs @ a-C:H with constant thickness of Cu and three thicknesses of Ni prepared by RF-PECVD system can be characterized using the multifractal geometry in correlation with the surface statistical parameters.

Multifractal characterization of water soluble copper phthalocyanine based films surfaces

This paper presents a multifractal approach to characterize the structural complexity of 3D surface roughness of CuTsPc films on the glass and quartz substrate, obtained with atomic force microscopy (AFM) analysis. CuTsPc films prepared by drop cast method were investigated. CuTsPc films surface roughness was studied by AFM in tapping-mode™, in an aqueous environment, on square areas of 100 μm2 and 2500 μm2. A detailed methodology for CuTsPc films surface multifractal characterization, which may be applied for AFM data, was also presented. Analysis of surface roughness revealed that CuTsPc films have a multifractal geometry at various magnifications. The generalized dimension Dq and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of CuTsPc films surface morphology at nanometer scale. Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters.

Fracture surface — fractal or multifractal?

Applying projective covering (PCM) and box-counting methods (for mutually perpendicular profiles), fracture surfaces of ductile and brittle materials were studied. Convergence of results of the compared fractal dimensions calculation methods was found and a multifractal nature of uneven surfaces was proved.

Morphological features in aluminum nitride epilayers prepared by magnetron sputtering

Abstract The aim of this study is to characterize the surface topography of aluminum nitride (AlN) epilayers prepared by magnetron sputtering using the surface statistical parameters, according to ISO 25178-2:2012. To understand the effect of temperature on the epilayer structure, the surface topography was investigated through atomic force microscopy (AFM). AFM data and analysis of surface statistical parameters indicated the dependence of morphology of the epilayers on their growth conditions. The surface statistical parameters provide important information about surface texture and are useful for manufacturers in developing AlN thin films with improved surface characteristics. These results are also important for understanding the nanoscale phenomena at the contacts between rough surfaces, such as the area of contact, the interfacial separation, and the adhesive and frictional properties.

Surface Roughness Characterization of Poly(methylmethacrylate) Films with Immobilized Eu(III) β-Diketonates by Fractal Analysis

The structural complexity of the 3-D surface of poly(methylmethacrylate) films with immobilized europium β-diketonates was studied by atomic force microscopy and fractal analysis. Fractal analysis of surface roughness revealed that the 3-D surface has fractal geometry at the nanometer scale. Poly(methylmethacrylate) (PMMA) as immobilization matrix is dense and uniform, and a tendency for formation of chain structures was observed. Fractal analysis can quantify key elements of 3-D surface roughness such as the fractal dimensions D f determined by the morphological envelopes method of the Eu(DBM)3 and Eu(DBM)3 · dpp nanostructures, which are not taken into account by traditional surface statistical parameters.

Morphology and Optical Properties of SiO2-Based Composite Thin Films with Immobilized Terbium(III) Complex with a Biscoumarin Derivative

The complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methyl)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(C25H15O7)3 · 5H2O, was successfully immobilized by a simple technique in transparent SiO2-based matrix. The films and monoliths obtained were studied by IR spectroscopy, fluorescent spectroscopy, and microscopy. The micromorphology of the films was studied by atomic force microscopy, proving their homogeneity. The 3-D surface of the films is very complex geometrically and appears relatively smooth, with very fine nano-asperities spread on the surface due to the preparation process. A detailed surface description of the surface morphology at nanometer scale using statistical parameters, according to ISO 25178-2: 2012, was made. The presence of the Tb(III) complex in the films and monoliths was proven by the characteristic emission bands of the Tb(III) ions. The lifetime of the immobilized Tb(III) complex was determined, showing better protection of the SiO2 matrix in the monoliths than with the films.

Surface morphology of titanium nitride thin films synthesized by DC reactive magnetron sputtering

Abstract In this paper the influence of temperature on the 3-D surface morphology of titanium nitride (TiN) thin films synthesized by DC reactive magnetron sputtering has been analyzed. The 3-D morphology variation of TiN thin films grown on p-type Si (100) wafers was investigated at four different deposition temperatures (473 K, 573 K, 673 K, 773 K) in order to evaluate the relation among the 3-D micro-textured surfaces. The 3-D surface morphology of TiN thin films was characterized by means of atomic force microscopy (AFM) and fractal analysis applied to the AFM data. The 3-D surface morphology revealed the fractal geometry of TiN thin films at nanometer scale. The global scale properties of 3-D surface geometry were quantitatively estimated using the fractal dimensions D, determined by the morphological envelopes method. The fractal dimension D increased with the substrate temperature variation from 2.36 (at 473 K) to 2.66 (at 673 K) and then decreased to 2.33 (at 773 K). The fractal analysis in correlation with the averaged power spectral density (surface) yielded better quantitative results of morphological changes in the TiN thin films caused by substrate temperature variations, which were more precise, detailed, coherent and reproducible. It can be inferred that fractal analysis can be easily applied for the investigation of morphology evolution of different film/substrate interface phases obtained using different thin-film technologies.

Film thickness effect on fractality of tin-doped In2O3 thin films

In this paper, based on atomic force microscopy (AFM) data the surface morphology of tin-doped In2O3 (ITO) thin films, prepared by electron beam deposition method on float glass substrates, was systematically investigated using the multifractal analysis. Topographical characterization of the ITO film surfaces was realized by a novel multifractal approach which may be applied for AFM data. Detailed surface characterization of the 3D surface topography was obtained using statistical parameters, according to the ISO 25178-2: 2012. Multifractal analysis of the film surfaces revealed that ITO thin films have a multifractal geometry. The generalized dimension Dq and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of film surfaces at nanometer scale. Our results showed that the larger spectrum width Δα (Δα = αmax − αmin) of the multifractal spectra f(α) is related to the larger surface roughness.

Fractal Analysis of AFM Images of the Surface of Bowman’s Membrane of the Human Cornea

The objective of this study is to further investigate the ultrastructural details of the surface of Bowman’s membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman’s membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman’s membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution.

Morphology of Co–Cr–Mo dental alloy surfaces polished by three different mechanical procedures

The present study aims at characterizing the three‐dimensional (3‐D) morphology of a Co–Cr–Mo dental alloy surface as a result of three different procedures used for polishing it. The sample surface morphology of the sampled surface was examined employing atomic force microscopy (AFM), statistical surface roughness parameters, and fractal analysis. An extra‐hard dental alloy of cobalt–chromium–molybdenum (Co–Cr–Mo) (Wironit®, from BEGO, Bremen, Germany) was prepared and moulded. Different polishing treatments were carried out on three groups of six samples each—a total of 18 samples. The first group contained six electropolished (EP) samples. The second group containing six samples went through a mechanical polishing process employing green rubber discs and a high shine polishing paste applied by a rotating black brush (BB). The third group comprising six samples as well went through a mechanical polishing process by means of green rubber discs, high shine polishing paste, and a rotating deer leather brush (DL). Fractal analysis on the basis of a computational algorithm applied to the AFM data was employed for the 3‐D quantitative characterization of the morphology of the sampled surfaces. The fractal dimension D (average ± standard deviation) of 3‐D surfaces for BB samples (2.19 ± 0.07) is lower than that of the DL samples (2.24 ± 0.08), which is still lower than that of the EP samples (2.27 ± 0.09). The results indicated the BB samples as presenting the lowest values of statistical surface roughness parameters, thus the best surface finish, while the EP samples yielded the highest values. Microsc. Res. Tech. 78:831–839, 2015.