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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Preliminary imaging in miniature MEMS electron microscope
摘要： A preliminary imaging concept in a miniature MEMS electron microscope is presented. The setup of the measurements is described and the mechanism of the imaging process is explained. Authors present also results of simulations and measurements concerning electron beam passing through thin silicon nitride membrane. The scattering angle of the electron beam is calculated. This parameter is both advantage and disadvantage for the imaging process. Preliminary (the first) image of copper wire placed over the membrane is presented.
关键词： miniature TEM,electron detection,imaging,MEMS
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - The stable and long lifetime planar field emission cathode made of a CNT ink
摘要： We present the planar cathode that is dedicated for the miniaturized transmission electron microscope, which all components are fabricated based on MEMS Si-glass technology processes. The cathode is made of a commercial CNT ink without addition of fillers, and results in the stable and long lifetime field emission of electrons.
关键词： planar cathode,MEMS,field emission,CNT ink,TEM
更新于2025-09-23 15:21:21
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Gram scale synthesis of monoclinic VO2 microcrystals by hydrothermal and argon annealing treatment
摘要： We report gram scale synthesis of 100 % phase fraction of VO2 (M) monoclinic in powder form with reversible phase transition by combining hydrothermal method and Ar annealing at high temperature. Optimization of single phase VO2 (M) growth and its phase transition characteristics have been analysed systematically by varying growth parameters such as time, synthesis temperature and post growth annealing conditions. Argon annealing of hydrothermally grown VO2 powders at 800°C found to play key role in obtaining VO2 (M) phase in gram scale with characteristic phase transition temperature of 68°C. In-situ TEM has been performed to investigate the microstructure and phase change across the annealing temperature. Detailed characterizations have been carried out to correlate the phases, microstructure and transition temperature of VO2 with respect to growth parameters.
关键词： metal-insulator transition,annealing treatment,monoclinic VO2,in-situ TEM,microcrystals,Scalable synthesis
更新于2025-09-23 15:21:21
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Effect of pH Values on the Structural, Optical and Electrical Properties of SnO2 Nanostructures
摘要： In the present work, we have synthesized the SnO2 nanostructures via precipitation method under optimal conditions at different pH values (3, 7 and 11) and studied the effect of different pH values on the structural, optical and electrical properties. The prepared samples are characterized by XRD, FESEM, TEM, PL, UV–Visible, FTIR spectroscopy and EIS measurements. XRD analysis reveals the tetragonal crystal structure for the prepared SnO2 nanostructures. TEM images show that the morphology of SnO2 nanostructures changed from spherical to hexagonal as pH values increased from 3 to 11. The deconvoluted PL spectra show various defects present in the synthesized samples that act as luminescent centers. The absorption spectra revealed that the maximum optical band-gap is obtained for SnO2 nanostructures synthesized using acidic solutions. The FTIR spectrum verifies the presence of stretching vibration mode of O-Sn-O bond and, stretching and bending bonds of O-H bonds in the prepared samples. A detailed exploration on frequency and temperature dependent impedance properties of SnO2 nanostructures has been done with the change in pH values.
关键词： Impedance spectroscopy,SnO2,PL,TEM,pH values,Nanostructures,FESEM
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - In-situ Characterization of Structure Evolution of Graphene During Field Emission
摘要： The structure stability of graphene field emitter is important for the performance of field emission devices. In this work, high dose electron beam illumination and high current field emission was applied on the graphene field emitter and its structure evolution and field emission characteristics were investigated using an in-situ TEM measurement system. The relation between structure and performance of graphene emitter was demonstrated. The interaction of electron and graphene was also discussed.
关键词： in-situ TEM,structure,field emission,Graphene
更新于2025-09-23 15:21:21
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Liquid-Cell Scanning Transmission Electron Microscopy and Fluorescence Correlation Spectroscopy of DNA-Directed Gold Nanoparticle Assemblies
摘要： In the use of solution-based 3D nanoarchitectures for optics, drug delivery, and cancer treatment, the precise nanoparticle architecture morphologies, architecture sizes, interparticle distances, and the assembly stability are all critical to their functionality. 3D nanoparticle architectures in solution are difficult to characterize, as few techniques can provide individualized information on interparticle spacing (defined by linkage molecule), nanoparticle assembly size, morphology, and identification of false aggregation. Bulk characterization techniques, including small angle x-ray scattering, can provide architecture sizes, though they are unable to precisely measure differences within interparticle spacings for individual architectures and can falsely measure assemblies caused by non-linkage grouped nanoparticles. Two solution-based characterization techniques were used to determine which assembly type and linkage length would produce the fastest assembly rate for large DNA-directed gold nanoparticle assemblies. In-situ liquid-cell scanning transmission electron microscopy (STEM), measured interparticle spacings between DNA-functionalized nanoparticles, and fluorescence correlation spectroscopy provided the bulk volume fraction of large and small assemblies for nanoparticle architectures that were assembled using two different types: (1) the hybrid assemblies join two complementary single-stranded DNA linkages, and (2) the bridged assemblies are comprised of single-stranded DNA (bridging component) that is double the length of two different complementary single-stranded DNA-functionalized gold nanoparticles (Fig. 1). Assembly times were tested at 24-hour intervals over 3 days. Statistics derived from the in-situ liquid-cell STEM images provided data for interparticle distance measurements, which identified the fraction of nanoparticles within the images acquired that were at the expected double-stranded DNA-binding distance of the linkages (varied in three distances for each of the two different architectures). In general, longer linkage lengths assembled in the shortest amount of time. The bridged assemblies formed fewer large architectures at 24-hours but ultimately assembled a greater fraction of nanoparticles, which was due to the longer functionalized DNA lengths for individual nanoparticles. Fluorescence correlation spectroscopy provided a bulk average of the gold nanoparticle assembly sizes over time, which supported the conclusions drawn from the in-situ liquid-cell STEM data. The microscopy provided sub-2 nanometer precision in the interparticle distances between gold nanoparticles in a solution environment. This coupled microscopy and spectroscopy characterization approach can provide more detailed information than bulk characterization methods.
关键词： gold,nanoparticle,DNA,FCS,assembly,liquid-cell TEM
更新于2025-09-23 15:21:21
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Influence of 4H-SiC substrate miscut on the epitaxy and microstructure of AlGaN/GaN heterostructures
摘要： AlGaN/GaN heterostructures were grown on “on-axis” and 2° off (0001) 4H-SiC substrates by metalorganic vapor phase epitaxy (MOVPE). Structural characterization was performed by transmission electron microscopy. The dislocation density, being greater in the on-axis case, is gradually reduced in the GaN layer and is forming dislocation loops in the lower region. Steps aligned along [11?00] in the off-axis case give rise to simultaneous defect formation. In the on-axis case, an almost zero density of steps is observed, with the main origin of defects probably being the orientation mismatch at the grain boundaries between the small not fully coalesced AlN grains. V-shaped formations are observed in the AlN nucleation layer, but are more frequent in the off-axis case, probably enhanced by the presence of steps. These V-shaped formations are completely overgrown by the GaN layer, during the subsequent deposition, presenting AlGaN areas in the walls of the defect, indicating an inter-diffusion between the layers. Finally, at the AlGaN/GaN heterostructure surface in the on-axis case, V-shapes are observed, with the AlN spacer and AlGaN (21% Al) thickness on relaxed GaN exceeding the critical thickness for relaxation. On the other hand, no relaxation in the form of V-shape creation is observed in the off-axis case, probably due to the smaller AlGaN thickness (less than 21% Al). The AlN spacer layer, grown in between the heterostructure, presents a uniform thickness and clear interfaces.
关键词： TEM,HEMT,SiC substrate,Heterostructure,AlGaN/GaN,HRTEM
更新于2025-09-23 15:21:21
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Deformation and removal of semiconductor and laser single crystals at extremely small scales
摘要： Semiconductor and laser single crystals are usually brittle and hard, which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications. Improvement of the surface integrity of a ground crystal can shorten the time of a subsequent polishing process, thus reducing the manufacturing cost. The development of cost-effective grinding technologies for those crystals requires an in-depth understanding of their deformation and removal mechanisms. As a result, a great deal of research efforts were directed towards studying this topic in the past two or three decades. In this review, we aimed to summarize the deformation and removal characteristics of representative semiconductor and laser single crystals in accordance with the scale of mechanical loading, especially at extremely small scales. Their removal mechanisms were critically examined based on the evidence obtained from high-resolution TEM analyses. The relationships between machining conditions and removal behaviors were discussed to provide a guidance for further advancing of the grinding technologies for those crystals.
关键词： semiconductor,laser crystal,deformation and removal,transmission electron microscopy (TEM),grinding
更新于2025-09-23 15:21:01
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Unraveling the Complex Nanomorphology of Ternary Organic Solar Cells with Multimodal Analytical Transmission Electron Microscopy
摘要： Elucidating the complex materials distribution in the active layers of ternary organic solar cells is one of the greatest challenges in the field of organic photovoltaics. Knowledge of the nanomorphology is key to understanding photophysical processes (e.g. charge separation, adjustment of the recombination mechanism as well as suppression of the radiationless and energetic losses) and thus improving the device performance. Here, we demonstrate for the first time the successful discrimination and spatial mapping of the active layer components of a ternary organic solar cell using analytical transmission electron microscopy. The material distribution of all three organic components was successfully visualized by multimodal imaging using complementary electron energy loss signals. A complete picture of the morphological aspects could be gained by studying the lateral and cross-sectional morphology as well as the morphology evolution as a function of the mixing ratio of the polymers. Finally, a correlation between the morphology, photophysical processes and device performance of the ternary and the reference binary system was achieved, explaining the differences of the power conversion efficiency (PCE) between the two systems.
关键词： device performance,EFTEM,morphology,TEM,Ternary organic solar cells
更新于2025-09-23 15:21:01
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Direct in situ TEM visualization and insight of the facet-dependent sintering behaviours of gold on TiO?
摘要： To prevent sintering of supported nanocatalysts is an important issue in nanocatalysis. A feasible way is to choose a suitable support. However, whether the metal-support interactions promote or prevent the sintering has not been fully identified due to the lack of confirmed evidences. Herein, we report on completely different sintering behaviours of Au nanoparticles on distinct anatase TiO2 surfaces by in situ TEM. The full in situ sintering processes of Au nanoparticles were visualized on TiO2 (101) surface, which coupled the Ostwald ripening and particle migration coalescence. In contrast, no sintering of Au on TiO2 anatase (001) surface was observed under the same conditions. This facet-dependent sintering mechanism is fully explained by the density function theory calculations. Our work not only offers the direct evidence of the important role of supports in the sintering process, but also provides insightful information for the design of sintering-resistant nanocatalysts.
关键词： in situ TEM,particle migration and coalescence (PMC),sintering,metal?support interaction (MSI),Au-TiO2,Ostwald ripening (OR)
更新于2025-09-23 15:21:01