Atomic Force Microscopy Images Research Articles

Highly Strained AlGaAs‐GaAsP Nanomembranes‐Based High‐Performance Diode

AbstractNanomembranes (NMs) made from single‐crystalline inorganic semiconductors offer unique properties, such as flexibility, transparency, and tunable bandgaps, making them suitable for complex device integration and next‐generation high‐power devices. In this study, the fabrication of a high‐performing emitter and base (E‐B) diode using transferable NMs of n‐AlGaAs/p‐GaAsP is demonstrated. Using a modified epitaxial lift‐off and transfer method, a single‐crystalline n‐AlGaAs/p‐GaAsP fragile NMs transfer onto ultrathin oxide (UO) grown GaN and Si substrates. The crystalline quality of the NMs is characterized by X‐ray diffraction and Raman spectroscopy techniques before and after transfer, no noticeable degradation has been found in its crystalline quality. In addition, atomic force microscopy and scanning electron microscopy images confirm the smooth surface and uniformity of the NMs over the whole substrate without any formation of cracks, respectively. Kelvin probe force microscopy demonstrates the formation of a nanoscale contact potential barrier at the interface of the E‐B diode. Furthermore, current–voltage (I–V) measurements demonstrate that the performance of the NM‐based E‐B diode is comparable to that of a rigid diode on the as‐grown sample. The findings highlight the potential of the epitaxial lift‐off and transfer method for the heterogeneous integration of III–V semiconductor materials to overcome the lattice‐mismatch limitations.

Finite element modelling of atomic force microscopy imaging on deformable surfaces.

Atomic force microscopy (AFM) provides a three-dimensional topographic representation of a sample surface, at nanometre resolution. Computational simulations can aid the interpretation of such representations, but have mostly been limited to cases where both the AFM probe and the sample are hard and not compressible. In many applications, however, the sample is soft and therefore deformed due to the force exerted by the AFM tip. Here we use finite element modelling (FEM) to study how the measured AFM topography relates to the surface structures of soft and compressible materials. Consistent with previous analytical studies, the measured elastic modulus in AFM is generally found to deviate from the elastic modulus of the sample material. By the analysis of simple surface geometries, the FEM modelling shows how measured mechanical and topographic features in AFM images depend on a combination of tip-sample geometry and indentation of the tip into the sample. Importantly for the interpretation of AFM data, nanoparticles may appear larger or smaller by a factor of two depending on tip size and indentation force; and a higher spatial resolution in AFM images does not necessarily coincide with a more accurate representation of the sample surface. These observations on simple surface geometries also extend to molecular-resolution AFM, as illustrated by comparing FEM results with experimental data acquired on DNA. Taken together, the FEM results provide a framework that aids the interpretation of surface topography and local mechanics as measured by AFM.

High-Resolution Atomic Force Microscopy Investigation of Alginate Hydrogel Materials in Aqueous Media.

Alginate hydrogels are frequently used in 3D bioprinting and tissue repair and regeneration. Establishing the structure-property-performance correlation of these materials would benefit significantly from high-resolution structural characterization in aqueous environments from the molecular level to continuum. This study overcomes technical challenges and enables high-resolution atomic force microscopy (AFM) imaging of hydrated alginate hydrogels in aqueous media. By combining a new sample preparation protocol with extremely gentle tapping mode AFM imaging, we characterized the morphology and regional mechanical properties of the hydrated alginate. Upon cross-linking, basic units of these hydrogel materials consist of egg-box dimers, which assemble into long fibrils. These fibrils congregate and pile up, forming a sponge-like structure, whose pore size and distribution depend on the cross-linking conditions. At the exterior, surface tension impacts the piling of fibrils, leading to stripe-like features. These structural features contribute to local, regional, and macroscopic mechanics. The outcome provides new insights into its structural characteristics from nanometers to tens of micrometers, i.e., at the dimensions pertaining to biomaterial and hydrogel-cell interactions. Collectively, the results advance our knowledge of the structure and mechanics from the nanometer to continuum, facilitating advanced applications in hydrogel biomaterials.

Green Synthesis of Zinc Oxide Nanoparticles Using Puerarin: Characterization, Antimicrobial Potential, Angiogenesis, and In Ovo Safety Profile Assessment.

Zinc oxide nanobiocomposites were successfully synthesized using a green synthesis approach. The process involves the utilization of the isoflavone puerarin, resulting in the formation of PUE-ZnO NPs. Physico-chemical and biological characterization techniques including X-ray dif-fraction (XRD), UV-vis spectroscopy, Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and in ovo methods were employed to study the main characteristics of this novel hybrid material. The PUE-ZnO NPs were confirmed to have been successfully synthesized with a UV absorption peak at 340 nm, the XRD analysis demonstrating their high purity and crystallinity. The energy band-gap value of 3.30 eV suggests possible photocatalytic properties. Both SEM and AFM images revealed the nanoparticle`s quasi-spherical shape, roughness, and size. Good tolerability and anti-irritative effects were recorded in ovo on the chorioallantoic membrane (CAM). According to these results, the synthesis of green PUE-ZnO NPs may be a promising future approach for biomedical and personal care applications.

On the Effect of Randomly Oriented Grain Growth on the Structure of Aluminum Thin Films Deposited via Magnetron Sputtering

The microstructure of aluminum thin films, including the grain morphology and surface roughness, are key parameters for improving the thermal or electrical properties and optical reflectance of films. The first step in optimizing these parameters is a thorough understanding of the grain growth mechanisms and film structure. To investigate these issues, thin aluminum films with thicknesses ranging from 25 to 280 nm were coated on SiOx/Si substrates at ambient temperature under high-vacuum conditions and a low argon pressure of 3 × 10−3 mbar (0.3 Pa) using the radio frequency magnetron sputtering method. Quantitative analyses of the surface roughness and nanograin characteristics were conducted using atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction. Changes in specular reflectance were measured using ultraviolet–visible and near-infrared spectroscopy. The low roughness values obtained from the AFM images resulted in high film reflectivity, even for thicker films. TEM and AFM results indicate monomodal, randomly oriented grain growth without a distinct columnar or spherical morphology. Using TEM cross-sectional images and the dependence of the grain size on the film thickness, we propose a grain growth mechanism based on the diffusion mobility of aluminum atoms through grain boundaries.

Effect of the Surface Morphology of a Metal Film on Ion Yields in a Platinum-Film Surface-Assisted Laser Desorption/Ionization Mass Spectrometry.

Matrix-assisted laser desorption ionization (MALDI) and surface-assisted laser desorption ionization (SALDI) mass spectrometry (MS), which can detect biomolecules and polymers, are widely used in biochemistry and material science. Some compounds that are difficult to ionize using MALDI can be ionized using SALDI. However, it is difficult to obtain high ion yields using SALDI/MS. In this study, a fabricated platinum (Pt) film with nanostructures on the sample surface using a sputtering method was evaluated to determine the optimal metal film for ion yield in SALDI. The surface morphology of the Pt film was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray reflectivity (XRR), and ultraviolet-visible-near-infrared (UV-Vis-NIR) reflectance spectroscopy. The SEM, AFM, and TEM images of the Pt film showed the deposited metal film giving high ion yields of polyethylene glycol (PEG) in SALDI/MS with a Pt film (Pt-SALDI) that had a rough surface. The densities and reflectivity of films were analyzed by XRR and UV-Vis-NIR. The higher ion yields of PEG were obtained by Pt-SALDI with the Pt films with lower densities and reflectivity. This indicates that the deposition conditions for the Pt films significantly improved the ion yield in Pt-SALDI/MS. The Pt-SALDI has ionization capabilities different from those of MALDI. Therefore, optimization of Pt film for SALDI/MS and the MS imaging allows more compounds to be detected with higher sensitivity.

Crystallization Control of Anionic Thiacalixarenes on Silicon Surface Coated with Cationic Poly(ethyleneimine).

Surface modification of solid substrates with organic molecules and polyelectrolytes is a promising strategy toward advanced soft materials due to the control of molecular arrangement and supramolecular organization; however, understanding the nature of interactions within the assembly is challenging. Here a facile approach to the control of the architecture of calixarene macrocycles on soft surfaces is presented through the interplay of weak interactions involving a solid silicon substrate, a cationic polyelectrolyte layer, and anionic sulfonatothiacalix[4]arene (STCA). Topological analysis of atomic force microscopy (AFM) images of STCA on silicon, as well as silicon wafers modified with neutral polyethylenimine (PEI) and cationic PEI-H+, indicates different surface morphology and assembly behavior of STCA on such substrates. Drop-casting a calixarene solution onto silicon induces the formation of chaotically oriented needle crystals. When there is globular PEI, a nucleation point for the STCA crystals is formed on the polyelectrolyte surface, which grows into rosette structures. In contrast, protonated PEI with a chain-like structure alters the self-organization of STCA on silicon surfaces, leading to a dense uniform fiber-like network. Density functional theory modeling of the system components' self-assembly reveals thermodynamically favorable face-to-face antiparallel aggregation of STCA monomers and contribution of H-bonding into PEI(PEI-H+)-STCA and Si-STCA association.

On the mechanism for work function change of gold electrodes by ultrathin polyethyleneimine (PEI) films: Effect of molecular order.

Polyethyleneimine (PEI) is a widely used cationic polyelectrolyte. In organic electronics, it is a universal surface modifier for shifting the electrode work function (Φ) and improving charge injection into electronic devices. This effect may depend on the conformation and dipolar order of the PEI ultrathin film, but their detailed experimental evaluation has not yet been reported. Thus, we used sum-frequency generation (SFG) spectroscopy to probe the net orientation of polar groups of PEI films on glass and gold. The films were fabricated by spin-coating from alcoholic solutions or by dip-coating from aqueous solutions of various pH values, with both branched (b-PEI) and linear (l-PEI) structures. The obtained SFG spectra and atomic force microscopy (AFM) images indicated that the conformational ordering of the PEI layers increases over the period of 14 days after fabrication, being slightly more pronounced for l-PEI vs b-PEI, and for dip-coating vs spin coating fabrication. Furthermore, both the pH of the dip-coating solutions and the substrate nature influence the final morphology and order of the adsorbed films. On glass, they are optimized at an intermediate pH 5, while on gold, the greatest homogeneity is observed at pH 2 and the largest dipolar order is observed at pH 10. The pH dependence of changes in the work function of gold by PEI (|ΔΦ|) suggests that the electronic contribution is dominant. Nevertheless, the evolution of the PEI dipolar ordering was accompanied by small variations of |ΔΦ|, suggesting that it does have a significant contribution, especially at conditions for which the electronic contribution is reduced.

Voltage-induced rearrangement in silver nanoparticles spatial distribution produced by EAFD method and its LSPR optimization

Abstract This paper presents a voltage-induced and thermal annealing rearrangement (VITAR) method based on modified electric field assisted film dissolution method as a flexible and powerful tool for manipulating nanoparticles spatial distribution based on drift and diffusion mechanisms that occur due to external DC voltage and thermal annealing processes. Different samples with various arrangements of external DC voltage and thermal annealing processes have been produced. The extinction and attenuated total reflection (ATR) spectra, as well as atomic force microscope (AFM) images, have been employed to investigate their optical and morphological properties. Four cases with arrangements of DV-Anl, DV-Anl-DV, DV-Anl-IV, and DV-IV-Anl have been studied. The AFM images show that by applying secondary voltage (direct or inverse voltage), it is possible to drift nanoparticles and change its morphology (size and shape) as well as surface and volume distributions. As a result, by applying a secondary direct voltage (in the DV-Anl-DV case), the surface density of nanoparticles decreases due to direct drift force. It is notable that in this case, the extinction peak and ATR depth have not significantly changed. By applying a secondary inverse voltage (in the DV-Anl-IV, and DV-IV-Anl cases), an increase in the surface density of the nanoparticles has been observed. Also, the extinction peak has increased, and the ATR depth has decreased in the DV-Anl-IV case, but in the DV-IV-Anl case, due to the uniform size of surface nanoparticles, the resonance power has shown a significant increase in both extinction and ATR spectra compared to other cases. The resulting changes in extinction and ATR spectra show that by using the VITAR process, the surface structure, morphology and its optical properties can be optimized and this method provides a great opportunity to enhance Localized Surface Plasmon Resonance effects, which can be employed in nano-optical devices.

Using natural starch granules to disperse solid beeswax into micron-sized droplets in emulsion

Use of beeswax together with starch to manufacture emulsion for fruit preservation has attracted wide attention in food packaging. In this paper, esterified starch (M-PS) granules prepared from natural potato starch were used to replace nanocrystals to prepare beeswax emulsion. The swelling property of M-PS granules was used to solve the problem of uneven dispersion of beeswax. Atomic force microscope (AFM) images showed that the network gel structure formed by M-PS granules limited the movement of beeswax droplets, and the droplet size was <1.0 μm. When the beeswax emulsion was added to the starch paste, the resulting starch-beeswax composite emulsion had a stable gel structure. Bananas were coated with the composite emulsion. After 7 days of storage, compared with the test data of bare bananas, the weight loss rate decreased by 42 %, the titratable acidity increased by 21 %, and the vitamin C was higher by 20 % of coated bananas. The formed coating effectively inhibited the decline of banana quality.

Supercapacitor performance of pure and Ni-doped CuO electrodes prepared by USP

Abstract In this study, the ultrasonic spray pyrolysis (USP) technique was employed to fabricate pure and 3% Ni-doped copper oxide (CuO) thin films (TFs) on In2O3/SnO2 (ITO) coated glass substrates. X-ray diffraction (XRD) analysis revealed that both pure and 3% Ni-doped CuO TFs exhibit a polycrystalline structure with the tenorite phase oriented preferentially along the (111) plane. The morphological properties of these TFs were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging. Energy dispersive x-ray spectroscopy (EDX) confirmed that the deposited TFs achieved the desired stoichiometry. The electrochemical properties of both pure and 3% Ni-doped CuO TFs were evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). At a current density of 1 A g−1, the specific capacitance of pure CuO TFs was found to be 78 F g−1, decreasing to 2 F g−1 at 10 A g−1. In contrast, Ni-doped CuO TFs exhibited a specific capacitance of 722 F g−1 at 1 A g−1 and 20 F g−1 at 10 A g−1. These results indicate that Ni-doping significantly enhances the specific capacitance values. The superior performance of Ni-doped CuO electrodes is attributed to their uniformly high porosity and improved electrical conductivity, demonstrating Ni-doped CuO as an optimal electrode material for pseudocapacitors.

A comparative study of polishing systems on optical properties and surface roughness of additively manufactured and conventional resin based composites

This study aimed to compare polishing systems on color stability, surface roughness, and gloss of additively manufactured permanent and conventional resin composites. Totally 250 disc specimens (6 mm*2 mm) were prepared from resin-based materials [G-ænial Posterior (GP), Clearfil Majesty Esthetic (CME), SonicFill-2 (SF), Tescera (Tes), and Crowntec (CT)]. Following baseline color (ΔE00), gloss (GU), and surface roughness (Ra) measurements, the specimens were randomly divided into 5 groups (n = 10/group) according to polishing systems: Control (mylar strips); OneGloss; OneGloss + Platina Hi-Gloss; OptiDisc; and OptiDisc + Platina Hi-Gloss. Specimens were immersed in coffee for 144 h following polishing. ΔE00, GU, and Ra measurements were repeated. Atomic force microscopy images were taken in all groups. Spearman’s rho correlation coefficient, Robust ANOVA, and Bonferroni correction were used for statistical analysis. Significance level was taken as p < 0.050. Significant differences in ΔE00 values were found among resin-based materials, polishing systems, and their interactions (p < 0.001,p < 0.01, and p = 0.001). Regardless of polishing system, the lowest ΔE00 values were observed in CT, while lowest gloss (GU) values were found in Tes. The lowest surface roughness (Ra) values were detected at OptiDisc group (p < 0.001). A single type of polishing system may not be sufficient to achieve optimal results in resin-based materials.

Impact of Biofilms on Surface Properties of Polymethyl Methacrylate (PMMA) Resins.

Poly(methyl methacrylate) (PMMA) resins are widely used in medical and dental applications. Their susceptibility to bacterial biofilm formation poses significant challenges related to material degradation and infection risk. This study investigated the effects of Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) biofilms on PMMA resin surface properties over a 45-day period at 35°C. The study examined various parameters including biofilm adhesion, morphology, surface roughness, hydrophobicity, solid fraction, and zeta potential. PMMA resin specimens were inoculated with bacteria and incubated for 45 days. Biofilm adhesion was visually assessed, while surface characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), roughness analysis, contact angle measurements, solid fraction determination, and zeta potential analysis. The P. aeruginosa and S. aureus isolates were selected based on their biofilm-positive characteristics, which were further confirmed using Congo red and biofilm formation assays through crystal violet staining and spectrophotometric analysis. The results demonstrated robust biofilm adhesion on PMMA surfaces. SEM and AFM imaging revealed textured surfaces with elevated structures and depressions within the biofilm matrix. Biofilm-exposed resins exhibited significantly increased roughness (Ra = 164.5 nm, Rq = 169.5 nm) and hydrophobicity (mean angle = 85.5°-90.5°) compared to control samples (Ra = 38-50 nm, angle = 55°). Solid fraction measurements indicated a denser biofilm matrix on exposed resins (0.908) compared to controls (0.65). Additionally, zeta potential values were more negative for biofilm-exposed resins (mean = -84.2 mV) than controls (-45.0 mV). These findings underscore the substantial alterations in PMMA resin surface properties induced by bacterial biofilms, emphasizing the critical need for strategies to prevent biofilm formation and mitigate associated risks in healthcare settings. Future research should focus on developing anti-biofilm coatings or treatments to preserve the integrity and functionality of PMMA materials.

Design of a Novel Peptide with Esterolytic Activity toward PET by Mimicking the Catalytic Motif of Serine Hydrolases.

Serine hydrolases have become increasingly important for recycling PET plastics. However, their properties are inherently constrained by their 3D structure, which in turn limits the conditions for their application. Considering peptides as catalysts for industrial depolymerization processes can help us to escape some of these limitations. In this article, a 25 amino acid thermostable peptide, HSH-25, was designed to depolymerize PET. The peptide incorporates a His-Ser-His motif, inspired by the catalytic triad found in the serine hydrolase family, into a β-hairpin fold. Stability of the fold was investigated by molecular dynamics simulations. Esterolytic activity of the peptide toward model substrates was detected within a pH range from pH 7 to pH 9.5. Degradation of polymeric PET substrates was confirmed by atomic force microscopy imaging on spin-coated PET thin films.

Formulation and evaluation of carrier-based dry powders containing budesonide and arformoterol for inhalation therapy

Asthma and Chronic Obstructive Pulmonary Disease (COPD) are major global health concerns, with inhalation therapy being a primary treatment method. Dry powder inhalers (DPIs) often face challenges related to particle aggregation, which can diminish drug delivery efficiency. This study investigates particle aggregation and aims to optimize the cohesion–adhesion balance to improve inhalation efficiency. Advanced techniques like atomic force microscopy and Raman imaging were used to analyze particle interactions, focusing on lactose ratios, particle morphology, and drug-drug interactions. The therapeutic efficacy of optimized formulations containing budesonide (BUD) and Arformoterol (AFT) was assessed using an asthma model, showing significant improvements in sRAW, neutrophil count, and tidal volume compared to the positive control, with p-values below 0.01. AFT exhibited comparable efficacy to Formoterol at half the dose. Additionally, pharmacokinetic studies demonstrated similar in vivo behavior between the drugs, confirming the therapeutic advantage of AFT, with p-values for AUC0−t and Cmax of .646 and .153, respectively. The fine particle fractions for AFT and BUD were 39.4% and 50.6%, respectively, indicating improved drug delivery efficiency and potential for better clinical outcomes in asthma and COPD patients.

Ultrathin SiONC passivation of c-Si by UHV thermal annealing in O₂/N₂: Chemical composition, morphology, and photoluminescence insights

This study investigates the impact of Ultra-High Vacuum (UHV) Thermal annealing in a N₂/O₂ atmosphere on the passivation of Ar ion etched crystalline silicon (c-Si) surfaces. A comprehensive analysis of the resulting ultrathin Silicon OxyNitride Carbide layer (SiONC) was conducted using X-ray Photoelectron Spectroscopy (XPS), Ultra-Violet Spectroscopy (UPS), Photoluminescence Spectroscopy (PL), and Atomic Force Microscopy (AFM). XPS revealed a significant transformation in chemical composition from a carbon-rich contaminated surface SiO1.02C2.98 to an oxygen- and nitrogen-containing passivated layer SiO0.13N0.10C0.28. UPS measurements elucidated changes in the electronic structure and Fermi level position at the c-Si/SiONC interface. AFM imaging demonstrated the formation of non-uniform SiONC islands, influencing surface morphology. Notably, PL spectroscopy indicated enhanced orange and red luminescence with energies of 2.0 and 1.73 eV, respectively, attributed to the SiONC layer. The enhanced luminescence, coupled with improved thermal stability and oxidation resistance, positions the SiONC layer as a promising material for advancing the performance of silicon-based optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). This study provides fundamental insights into the correlation between the chemical, electronic, and morphological properties of the SiONC layer and its potential for improving c-Si device performance.

Toward crack-free AlN growth on silicon (111) by introducing boron incorporated buffer layer via MOCVD

High-quality aluminum nitride (AlN) films on silicon substrates are crucial for various applications due to their inherent properties as wide-bandgap semiconductors, cost-effectiveness, and compatibility with silicon-based circuits. Nonetheless, producing high-quality and crack-free AlN on silicon presents significant challenges due to the stress caused by lattice and thermal expansion mismatches. This study introduces a method to mitigate these challenges by incorporating a boron precursor during the metalorganic chemical vapor deposition process to form a BAlN buffer layer. Analytical techniques, such as secondary ion mass spectrometry, atomic force microscopy imaging, XRD rocking curves, reciprocal space map, and Raman spectroscopy, indicate that the BAlN buffer layer promotes the enlargement of seed crystal size, which effectively delays AlN coalescence, mitigates accumulated tensile stress, and enhances the overall crystal quality. Employing this technique has produced a 520 nm thick, crack-free AlN film on silicon (111) with high crystal quality, achieving full width at half maximum values of only 0.2° and 0.3° for XRC (002) and (102), respectively.

Electrophoretic deposition of novel antibacterial and biocompatible polydopamine and ZIF-8 hybrid composite coating on anodized Ti-6Al-4V alloy with silane primary substrate

Production of biocompatible and corrosion resistance dental implant is a requirement in the modern dental science. In this work, the Ti-6Al-4V was used alloy for the dental implant application that has investigated to make it more corrosion resistive and antibacterial with electrophoretic deposition of silane precursor solution that made of acidic solution of tetraethyl orthosilicate (TEOS) and methyl three ethoxy silane (MTES). The optimized silane coating has been achieved with 30 V, 30 min and at 100 °C ramped annealing by comparison of Taffel analysis and electrochemical impedance spectroscopy (EIS). Also, a new nanocomposite including polydopamine (PDA) and zeolite imidazole frame work composed from Zn (NO3)2 .6H2O and 2-methylimidazole (ZIF-8) that name PDA@ZIF-8 has been used as biocompatible and corrosion resistance amplifier to the precursor solution and used in the multilayer deposition process. The morphology analysis including atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) imaging and the obtained parameters show that coating has appropriate roughness that could increase the bounding of implant. A good adhesion strength has been determined for the two-layers silane coating with PDA@ZIF-8 according to the pull- off test. On the other hand, the antibacterial analysis indicate that the coating is an effective material for S. mutans and E. coli reduction that is another criterion for the dental implant materials. The results was introduced the coated Ti-6Al-4V could be used as corrosion resistive and antibacterial dental implant material.

Atomic force microscopy wide-field scanning imaging using homography matrix optimization

During the offline combination of multiple atomic force microscopy (AFM) images, changes in probe displacement can be affected by dynamic noise, leading to dislocation and tearing in the stitching. To overcome this, we designed a homography matrix optimization method to describe the relative positional relationship between images by constructing the original image matrix and applying singular value decomposition to denoise the homography matrix. Additionally, we implemented a scale-invariant feature transform (SIFT) to extract feature points. To verify the effectiveness of this method, the SIFT + RANSAC (R), SIFT + affine transformation (AT), and oriented FAST and rotated BRIEF (ORB) algorithms were compared with the proposed algorithm. The experimental results demonstrate that the proposed method precisely computes the transformation matrix, thereby guaranteeing the geometric consistency of mosaic imaging. The proposed method preserves the intricate details of the original image and enhances the stitching quality of wide-field images.

Fractal analyses of AlxGa1−xN thin film surfaces on AlN at different annealing temperatures

The determination of heteromorphological structures formed on the surface during annealing of AlxGa1−xN thin film grown on sapphire substrate using the metal organic chemical vapor deposition technique at different temperatures was investigated by fractal analysis method. The images of the surfaces of the thin films were taken by atomic force microscopy (AFM) at temperatures of 900, 1000, 1050 and 1200 °C respectively. AFM images were digitised in bitmap format according to the annealing temperatures. It was determined that the fractal dimensions obtained a linear correlation with the annealing temperatures. The results confirm the hypothesis that surface relaxation by the thermal action can produce fractal-like structures at particle or cluster boundaries. It is found that the observed cluster formation of superficial particles decreases as increasing temperature. The increase in temperature reduces the rate of superficial particle coating. To determine the surface roughness of the AlxGa1−xN thin film according to the annealing temperature, the AFM images were digitized in tagged image file format and the statistical root mean square, mean value, mean roughness, skewness and kurtosis values of the films were calculated. The roughness is a result of the thin film surface heteromorphology formed due to the specific annealing process. It is proved that the fractal dimensions of the AlxGa1−xN thin film increase as the annealing temperature rises. The particles coalesce on the surface and cluster in different types and sizes at each different annealing temperature, forming islets of different sizes. The skewness and kurtosis values show a different and irregular change.