Topographic characterization of zirconia-based ceramics by atomic force microscopy: A case study on different laser irradiations

Advanced nano-texture, optical bandgap, and Urbach energy analysis of NiO/Si heterojunctions

Due to the large number of industrial applications of transparent conductive oxides (TCOs), this study focuses on one of the most important metal oxides. The RF-magnetron sputtering method was used to fabricate NiO thin films on both quartz and silicon substrates at room temperature under flow of Argon and Oxygen. The sputtered samples were annealed in N₂ atmosphere at 400, 500, and 600 °C for 2 hours. Using the AFM micrographs and WSXM 4.0 software, the basic surface parameters, including root mean square roughness, average roughness, kurtosis, skewness, etc., were computed. Advanced surface parameters were obtained by the Shannon entropy through a developed algorithm, and the power spectral density and fractal succolarity were extracted by related methods. Optical properties were studied using a transmittance spectrum to achieve the optical bandgap, absorption coefficient, Urbach energy, and other optical parameters. Photoluminescence properties also showed interesting results in accordance with optical properties. Finally, electrical characterizations and I-V measurements of the NiO/Si heterojunction device demonstrated that it can be used as a good diode device.

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.

Nanoscale surface dynamics of spatial patterns of polymeric bilayered particles loaded with essential oil

Gelatin/PCL bilayered particles loaded with Piper nigrum essential oil was synthesized aiming to access their morphological and surface dynamic patterns. Atomic force microscopy (AFM) was applied to investigate the 3D morphology and multifractal aspects of the particles surface. The AFM maps revealed spherical surfaces and well dispersed particles, besides a rougher surface on the loaded system. Minkowski functionals showed that shape of the rough peaks was similar in the unloaded and loaded systems; however, the presence of deep valleys on the loaded particles revealed their rougher pattern. Multifractal analysis revealed that unloaded and loaded particles presented multifractal behavior with different surface dynamics. The loaded surface presented a greater width of the multifractal spectrum and smaller difference of fractal dimensions, confirming their more vertically growing. These results can be useful in the development of novel polymeric-based particles loaded with essential oil. Their unique surface dynamics can provide enhanced physical properties and performance in emerging biotechnological applications.

Vapor Barrier Properties of Cold Plasma Treated Corn Starch Films

The development and efficient production of effective bioplastics is a hot topic, required to face up to the issue of the difficult disposal of plastics derived from oil. Among the different natural sources of bioplastics, starch is one of the most promising. However, for most applications, the proper mastering of the surface properties of bioplastic is necessary. We report about the surface modification of extruded corn starch films by means of cold plasma based on helium (He) and hexamethyldisiloxane (HMDSO). The differently treated surfaces were functionally characterized in wettability and water absorption. The nanoscale morphology was assessed by scanning electron microscopy and atomic force microscopy. The obtained images were analyzed by advanced figures describing both texture and amplitude parameters, including fractal behavior. The combined treatment (He/HMDSO) resulted in more homogeneous films with smaller, better-distributed grains compared to the case wherein He was not used. Despite the different morphologies observed, starch coated by HMDSO alone and by He/HMDSO presented similar hydrophobic character, with contact angles higher than 110°. Plasma treatment with HMDSO and He/HMDSO resulted in a significant reduction of absorbed water content without reduction of water vapor permeability. The nanotexture of the films did not present statistically significant differences, in terms of spatial complexities, dominant spatial frequencies, homogeneous void distribution, and surface percolation.

The electrophoretic deposition of TiB2 nanoparticles produced by pulsed laser ablation: Case study on microstructural features and micromorphology properties

In the last decade, laser Ablation technique (Nd:YAG) has been considered as a perfect method for producing nanostructures with high purity. In the present study, Titanium diboride nanoparticles (TiB₂ NPs) have been deposited on Aluminum (Al) and their micromorphology and microstructural properties have been investigated. The synthesis of TiB₂ NPs has been carried out by the Laser Ablation technique (Nd:YAG) which has not been reported so far. Moreover, the effects of laser energy on improving the synthesis of TiB₂ NPs have been examined. In this regard, five samples of TiB₂ NPs were prepared by Laser Ablation method in different values of laser fluency in the range of 0.4-1.2 J/cm² . The structural properties of prepared nanoparticles were detected by grazing incidence X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The morphology of samples was also investigated by field effect scanning electron microscopy. The results demonstrate the formation of spherical nanoparticles in all samples. Based on the results of the GIXRD patterns, pulsed laser energy is an effective parameter for the size of ablated nanoparticles. As can be seen, increasing the energy of laser beam decreases the average size of nanoparticles from 79.41 to 4 nm. As the next step, the as-prepared nanoparticles were deposited on Aluminum substrate with electrophoretic deposition technique at constant applied voltage (30 Volt) and constant deposition time (30 min). The X-ray diffraction pattern of TiB₂ NPs deposited onto Al substrate confirmed the formation of the TiB₂ thin films on all Al substrates. Also, the roughness and average particle size of deposited films were measured by atomic force microscopy images and MountainsMap® Premium software. Increasing the fluency of laser beam made the surface more irregular and the maximum value of fractal dimension and hence, the most irregular topography has been observed in the sample produced by maximum laser fluency. RESEARCH HIGHLIGHTS: Titanium diboride nanoparticles have been synthesized by the laser ablation technique. The effects of laser energy on improving the synthesis of TiB₂ NPs have been investigated. The micromorphology of samples have been investigated by analyzing AFM and SEM images.

Investigation of the morphological and fractal behavior at nanoscale of patterning lines by scratching in an atomic force microscope

In this work, the topographical effect of the scratching trajectory and the feed direction on the formation of lithographed lines on the (001) InP surface was investigated using an atomic force microscope (AFM) tip-based nanomachining approach. Nanoscratching tests were carried out using the sharp face of a diamond AFM tip in contact mode. From the topographic maps obtained by AFM, several morphological and fractal parameters were obtained and analyzed. Surface morphology presented a surface smoothing for surfaces with scratches produced in [011] and [001] directions. The height parameters confirmed this behavior because scratches in [001] direction exhibited lower roughness. Moreover, this scratch direction promoted the height distribution most symmetrical and platykurtic. The other morphological parameters revealed that this direction provided a more irregular surface (smaller S_mc and S_xp ), peak distribution, denser and pointed, smaller portion of material in the core, less deep furrows, higher spatial frequency components, and high isotropy. Fractal parameters revealed that FRE90 has the highest spatial complexity, it is dominated by higher spatial frequencies, and has the lowest surface percolation. Furthermore, all samples exhibited high topographic uniformity.

The effect of applied electric field on the micromorphology of Pt nanoparticles synthesized by laser ablation

In the present study, laser ablation technique (Nd:YAG) has been applied to synthesize platinum nanoparticles (NPs). Also, the effect of applied electric field on the physical, structural, and morphological properties of Pt NPs has been investigated during the nanosecond pulsed laser ablation of platinum. Based on the results extracted from TEM and scanning electron microscopy images, the formation of high percentage of NPs with spherical shape is demonstrated in all samples. The increase of applied electric field creates few rectangular, hexagonal, and rhombic NPs with the average size decreased from 20 to 9 nm. The significant influence of increasing electric field is also observed in UV-vis spectra by appearing the blue shift of the localized surface plasmon resonance peak. The UV-vis spectra also confirm the metallic nature of Pt NPs and the existence of inhomogeneous-sized particles and the coagulation of particle because of the long tail in higher wavelengths. In addition, atomic force microscopy images have been analyzed through MountainsMap Premium program and fractal dimension. As can be seen, increasing the applied electric field make the surface more irregular and the maximum value of D_f reveals the most irregular topography for sample with 50 V/cm electric field. Finally, the bending and stretching frequencies of the functional bending groups connected to the NPs surface have been characterized by Fourier transform infrared spectroscopy. Electrical field-assisted laser ablation in liquids method allows a better control of the size, morphology, structure, and chemical composition of nanoparticles.

Investigation of Stereometric and Fractal Patterns of Spin-Coated LuMnO3 Thin Films

In this paper, we have performed qualitative and quantitative analysis of LuMnO3 thin films surfaces, deposited by spin coating over Pt(111)/TiO2/SiO2/Si substrates, to evaluate their spatial patterns as a function of the film’s sintering temperature. Atomic force microscopy was employed to obtain topographic maps that were extensively analyzed via image processing techniques and mathematical tools. 3D (three-dimensional) topographical images revealed that films sintered at 650°C and 750°C presented the formation of smoother surfaces, while the film sintered at 850°C displayed a rougher surface with a root mean square roughness of ∼2.5 nm. On the other direction, the height distribution of the surface for all films has similar asymmetries and shape, although the film sintered using the highest temperature showed the lower density of rough peaks and a sharper peak shape. The advanced fractal parameters revealed that the film sintered at 850°C is dominated by low spatial frequencies, showing less spatial complexity, higher microtexture homogeneity, and uniform height distribution. These results suggest that the combination of stereometric and fractal parameters can be especially useful for identification of unique topographic spatial patterns in LuMnO3 thin films, helping in their implementation in technological applications, such as photovoltaic solar cells and information magnetic date storage and spintronic devices.

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

Multiferroic systems are of great interest for technological applications. To improve the fabrication of thin films, stereometric and fractal analysis of surface morphology have been extensively performed to understand the influence of physical parameters on the quality of spatial patterns. In this work, GaMnO3 was synthesized and thin films were deposited on Pt(111)/TiO2/SiO2/Si substrates using a spin coating apparatus to study the correlation between their stereometric and fractal parameters. All films were studied by X-ray diffraction (XRD), where the structure and microstructure of the film sintered at 850 °C was investigated by Rietveld refinement. Topographic maps of the films were obtained using an atomic force microscope (AFM) in tapping mode. The results show that the film sintered at 850 °C exhibited a clear formation of a GdMnO3 orthorhombic structure with crystallite size of ~14 nm and a microstrain higher than other values reported in the literature. Its surface morphology presented a rougher topography, which was confirmed by the height parameters. Topographic differences due to different asymmetries and shapes of the height distributions between the films were observed. Specific stereometric parameters also showed differences in the morphology and microtexture of the films. Qualitative rendering obtained by commercial image processing software revealed substantial differences between the microtextures of the films. Fractal and advanced fractal parameters showed that the film sintered at 850 °C had greater spatial complexity, which was due to their higher topographic roughness, lower surface percolation and greater topographic uniformity, being dominated by low dominant special frequencies. Our combination of stereometric and fractal measurements can be useful to improve the fabrication process by optimizing spatial patterns as a function of the sintering temperature of the film.

The effect of deposition times in DC-magnetron sputtering on micromorphology of TiO2 thin films

TiO₂ thin films have been prepared by DC-magnetron sputtering process with various deposition times (8, 14, 16, and 20 min) and the micromorphology of their surface has been investigated by means of multifractal analysis. As the main purpose of the manuscript, the topography of all samples are examined by atomic force microscopy (AFM) through the Mountains Map® Premium software which characterizes motifs of significant peaks and pits through stereometric data by the watershed segmentation algorithm. In addition, multifractal features of samples provide deeper insight into texture characteristics and used as the supplementary of the results.

3D micromorphology evaluation of kefir microbial films loaded with extract of Amazon rainforest fruit Cupuaçu

We performed qualitative and quantitative analysis of surfaces of kefir biofilms loaded with Amazon rainforest fruit extract. Scanning electron microscopy and atomic force microscopy were used to evaluate the micromorphology of the biofilms. The films surface displayed a lower density of microorganisms (∼ 0.061 microorganisms/μm²) for the lowest concentration of fruit extract, however, a greater density (∼0.220 microorganisms/μm²) was observed for the higher concentration. Height stereometric parameters revealed that the biofilms with the highest concentration presented the highest roughness. However, almost all the stereometric parameters related to texture showed no significant difference. Furthermore, the Hurst coefficients of the average power spectrum density were similar for all biofilms. Fractal parameters confirmed that higher concentrations of fruit extract induced a superior topographic irregularity. However, fractal lacunarity does not show any significant difference confirming the similarity of the microtextures. Moreover, fractal succolarity and surface entropy exhibited values that suggested ideal percolation and strong topographic uniformity, respectively, indicating that these films can uniformly adhere to other surfaces. Our results confirm that the stereometric and fractal parameters can be relevant for the surface characterization of microbial films, which can be of great importance to the biomedical field.