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Morphological study of InGaN on GaN substrate by supersaturation
摘要： The morphology of thin InGaN layers grown on c-plane GaN substrates by metalorganic vapor phase epitaxy (MOVPE) has been studied by atomic force microscopy. Three different morphologies appeared, a stepped surface, large flat two-dimensional (2D) islands and small high three-dimensional (3D) dots. Low growth temperature and high growth rate (i.e. increased vapor supersaturation) changed the InGaN morphology from steps to 2D islands and then 3D dots (when exceeding the critical thickness for 3D dots). Larger miscut angle of GaN substrate changed the morphology from 2D islands to step by decreasing the surface supersaturation of individual terraces. InGaN layers with a stepped morphology had the highest internal quantum efficiency at similar InN mole fraction. InGaN grown on GaN substrate more easily achieved a stepped morphology compared to InGaN on GaN/sapphire templates.
关键词： A3. Metalorganic vapor phase epitaxy,B2. Semiconducting III-V materials,A1. Crystal morphology,B1. Nitride
更新于2025-09-23 15:22:29
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Room-temperature ferromagnetism and morphology evolution of SnO2 flower-like microparticles by Zn-doping
摘要： We report on the growth of undoped and Zn-doped flower-like microparticles, which are constituted of SnO2 acicular nanoparticles (NPs) aggregated by one of their ends. NPs were synthesized by the hydrothermal method. The morphology of the NPs progressively changes from truncated rods to sharp needles by the effect of Zn doping. This morphology evolution is attributed to an increase of the surface free energy of the NPs' facets and to a modification of the growth front direction. Undoped samples exhibit a very low magnetization attributed to single positive charged oxygen vacancies, while Zn-doped samples exhibit ferromagnetic ordering due to Zn atoms in Sn substitutional positions (ZnSn). Thermal treatment under reducing atmosphere leads to the creation of an excess of VO conducting to a reduction of the magnetization, demonstrating that ferromagnetism in Zn-doped SnO2 NPs is attributed to ZnSn defects and to the octahedrally coordinated oxygen atoms.
关键词： Magnetization,Oxygen vacancies,SnO2 nanoparticles,Morphology,Zn-doped
更新于2025-09-23 15:22:29
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[ACM Press Proceedings of the 14th EAI International Conference - Melbourne, VIC, Australia (2017.11.07-2017.11.10)] Proceedings of the 14th EAI International Conference on Mobile and Ubiquitous Systems Computing Networking and Services - Sensor Agnostic Photoplethysmogram Signal Quality Assessment using Morphological Analysis
摘要： In this article, we propose a method to assess the clinical usability of fingertip Photoplethysmogram (PPG) waveform, collected from medical grade oximeter (train data) and smartphone (test data). We introduce a set of novel Signal Quality Indices (SQIs) to represent the noise characteristics of the PPG waveform. The SQIs are presented to a random forest classifier to discriminate between clean and noisy signals. The proposed method was evaluated on datasets annotated by four experts, resulting into a sensitivity and specificity of (92 + ? 4.7 % , 95 + ? 4.6 % , 95.4 + ? 3.1 %) on train and test data respectively. Further we applied the proposed method on PPG waveform of clinically proven control and disease population of Coronary Artery Disease (CAD), which resulted into (77 %,77 %) of sensitivity and specificity respectively.
关键词： Artefact,Noise Detection,Photoplethysmogram,Wearable Sensors,Morphology,Mobile Health
更新于2025-09-23 15:22:29
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Effect of NaN<sub>3</sub> Addition Content on NaCl-NaF Medium Nitridation Synthesis β-Sialon Powders
摘要： β-Sialon powders were synthesized via salt-assisted nitridation synthesis from Al, Si, SiO2 powders and molten salt medium (NaCl and NaF) with the addition of different content of NaN3 at different temperature for 3 h. NaN3 were employed as auxiliary nitrogen source which effectively provide sufficient nitrogen. The results indicated that the growth of β-Sialon powders had better effect when the NaN3 was added. And the β-Sialon powders grew more completely and the morphology of β-Sialon powders showed the rod-like crystal with hexagonal smooth tips instead of conical tips. In addition, the products displayed different sizes when the content of NaN3 was changed. These results of this work suggested that β-Sialon could be synthesized with specific morphology by adding different content of NaN3.
关键词： β-Sialon,synthesis,Morphology,nitridation,salt-assisted
更新于2025-09-23 15:22:29
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Formation of Composite Polyaniline and Graphene Oxide by Physical Mixture Method
摘要： The development of polyaniline and graphene oxide composites aims to join the unique properties of each material for aerospace applications. The present paper demonstrates an easy and quick method, compared to the ones found in the literature, to obtain a composite made with polyaniline doped with dodecylbenzenesulfonic acid, a combination commonly called polyaniline, and graphene oxide. Nowadays, the most common studied methods are electrochemistry and in situ chemical polymerization. Differently from these methods, the films were obtained by a physical mixture of equimolar suspension of graphene oxide (4 mg/mL) with 3 concentrations of polyaniline powder: 25; 50 and 75%, being compared to pure graphene oxide and polyaniline. The morphology and structure behavior of all the films were studied, besides the bonding nature between both materials. The films were analyzed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The apparent interaction between graphene oxide corrugated sheets and polyaniline grains was verified by scanning electron microscopy images. It can be noticed, as the concentration of polyaniline increases, that more polymer was entrapped. To prove the formation of polyaniline/graphene oxide composite, X-ray diffraction and Fourier transform infrared spectroscopy techniques demonstrated the changes on graphene oxide crystallographic plans and on the chemical bonding between polyaniline and graphene oxide, suggesting an interaction between polyaniline and graphene oxide, especially in the composite with 50% polyaniline/50% graphene oxide. Differential scanning calorimetry was used to highlight this effect through the increase in thermal stability. The method of physical mixture was efficient to obtain the polyaniline/graphene oxide composites.
关键词： Structure,DSC,FT-IR,Morphology,Polyaniline,Graphene oxide
更新于2025-09-23 15:22:29
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Hetero-Orientation Epitaxial Growth of TiO2 Splats on Polycrystalline TiO2 Substrate
摘要： In the present study, the effect of titania (TiO2) substrate grain size and orientation on the epitaxial growth of TiO2 splat was investigated. Interestingly, the splat presented comparable grain size with that of substrate, indicating the hereditary feature of grain size. In addition, hetero- and homo-orientation epitaxial growth was observed at deposition temperatures below 400 °C and above 500 °C, respectively. The preferential growth of high-energy (001) face was also observed at low deposition temperatures (≤ 400 °C), which was found to result from dynamic nonequilibrium effect during the thermal spray deposition. Moreover, thermal spray deposition paves the way for a new approach to prepare high-energy (001) facets of TiO2 crystals.
关键词： hetero-orientation epitaxial growth,preferential growth,crystal morphology,homo-orientation epitaxial growth,deposition temperature,hereditary feature
更新于2025-09-23 15:22:29
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Synergistic effect of Ag and ZnO nanoparticles on polyaniline incorporated epoxy/2pack coatings for splash zone applications
摘要： In this work, epoxy/2pack coatings containing polyaniline (PANI) in combination with Ag and ZnO nanoparticles have been synthesized. The nanoparticles were incorporated with bisphenol-A diglycidyl ether epoxy resin and polyamino-amide. The mechanical properties of the fabricated coatings, such as the pendulum hardness, scratch resistance, and impact strength, were studied. The composition of the fabricated coatings was confirmed by attenuated total reflectance infrared spectroscopy measurements. The thermal degradation and indentations were characterized through the use of differential scanning calorimetry and nano-indentation techniques, respectively. The surface morphology of the fabricated coatings was characterized using field-emission scanning electron microscopy. The synergistic effects of the Ag and ZnO nanoparticles on the corrosion resistance of the coatings after different exposure periods in 3.5% NaCl solutions were determined by electrochemical impedance spectroscopy. All the results were consistent with one another and confirmed that the addition of Ag and ZnO nanoparticles improved the mechanical properties of the coatings. This effect also led to a notable increase in the corrosion resistance of the PANI coatings.
关键词： Nanoparticles,Polyaniline,Nano-indentation,Corrosion resistance,Epoxy coatings,Surface morphology
更新于2025-09-23 15:22:29
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A Label-free Multicolor Optical Surface Tomography (ALMOST) imaging method for nontransparent 3D samples
摘要： Background: Current mesoscale 3D imaging techniques are limited to transparent or cleared samples or require the use of X-rays. This is a severe limitation for many research areas, as the 3D color surface morphology of opaque samples—for example, intact adult Drosophila, Xenopus embryos, and other non-transparent samples—cannot be assessed. We have developed “ALMOST,” a novel optical method for 3D surface imaging of reflective opaque objects utilizing an optical projection tomography device in combination with oblique illumination and optical filters. Results: As well as demonstrating image formation, we provide background information and explain the reconstruction—and consequent rendering—using a standard filtered back projection algorithm and 3D software. We expanded our approach to fluorescence and multi-channel spectral imaging, validating our results with micro-computed tomography. Different biological and inorganic test samples were used to highlight the versatility of our approach. To further demonstrate the applicability of ALMOST, we explored the muscle-induced form change of the Drosophila larva, imaged adult Drosophila, dynamically visualized the closure of neural folds during neurulation of live Xenopus embryos, and showed the complementarity of our approach by comparison with transmitted light and fluorescence OPT imaging of a Xenopus tadpole. Conclusion: Thus, our new modality for spectral/color, macro/mesoscopic 3D imaging can be applied to a variety of model organisms and enables the longitudinal surface dynamics during development to be revealed.
关键词： Tomography,Opaque samples,Real color,Label-free,3D imaging,Mesoscale,Morphology
更新于2025-09-23 15:22:29
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An Improved Top-Hat Filter with Sloped Brim for Extracting Ground Points from Airborne Lidar Point Clouds
摘要： Airborne light detection and ranging (lidar) has become a powerful support for acquiring geospatial data in numerous geospatial applications and analyses. However, the process of extracting ground points accurately and effectively from raw point clouds remains a big challenge. This study presents an improved top-hat filter with a sloped brim to enhance the robustness of ground point extraction for complex objects and terrains. The top-hat transformation is executed and the elevation change intensity of the transitions between the obtained top-hats and outer brims is inspected to suppress the omission error caused by protruding terrain features. Finally, the nonground objects of complex structures, such as multilayer buildings, are identified by the brim filter that is extended outward. The performance of the proposed filter in various environments is evaluated using diverse datasets with difficult cases. The comparison of the proposed filter with the commercial software Terrasolid TerraScan and other popular filtering algorithms demonstrates the applicability and effectiveness of this filter. Experimental results show that the proposed filter has great promise in terms of its application in various types of landscapes. Abrupt terrain features with dramatic elevation changes are well preserved, and diverse objects with complicated shapes are effectively removed. This filter has minimal omission and commission error oscillation for different test areas and thus demonstrates a stable and reliable performance in diverse landscapes. In addition, the proposed algorithm has high computational efficiency because of its simple and efficient data structure and implementation.
关键词： point cloud,top-hat transformation,mathematical morphology,filtering,lidar
更新于2025-09-23 15:22:29
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Understanding Film-to-Stripe Transition of Conjugated Polymers Driven by Meniscus Instability
摘要： Meniscus instability during meniscus-guided solution coating and printing of conjugated polymers has significant impact on the deposit morphology and the charge transport characteristics. The lack of quantitative investigation on meniscus-instability-induced morphology transition for conjugated polymers hindered the ability to precisely control conjugated polymer deposition for desired applications. Herein, we report a film-to-stripe morphology transition caused by stick-and-slip meniscus instability during solution coating seen in multiple donor-acceptor polymer systems. We observe the coexistence of film and stripe morphologies at the critical coating speed. Surprisingly, higher charge carrier mobility is measured in transistors fabricated from stripes despite their same deposition condition as the films at the critical speed. To understand the origin of the morphology transition, we further construct a generalizable surface free energy model to validate the hypothesis that the morphology transition occurs to minimize the system surface free energy. As the system surface free energy varies during a stick-and-slip cycle, we focus on evaluating the maximum surface free energy at a given condition, which corresponds to the sticking state right before slipping. Indeed, we observe increase of the maximum system surface free energy with increase in coating speed prior to film-to-stripe morphology transition and abrupt drop in the maximum system surface free energy post-transition when the coating speed is further increased, which is associated with reduced meniscus length during stripe deposition. Such energetic change originates from the competition between pinning and depinning forces on a partial wetting substrate which underpins the film-to-stripe transition. This work establishes a quantitative approach for understanding meniscus-instability-induced morphology transition during solution coating. The mechanistic understanding may further facilitate the use of meniscus instability for lithography-free patterning or to suppress instability for highly homogeneous thin film deposition.
关键词： conjugated polymer,meniscus instability,printed electronics,morphology transition,solution coating
更新于2025-09-23 15:21:21