- 标题
- 摘要
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- 实验方案
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Ar-Plasma-Modulated Optical Reset in the SiO <sub/>2</sub> /Cu Conductive-Bridge Resistive Memory Stack
摘要： Our study using conductive atomic force microscope shows that the resistive switching voltage in the SiO2/Cu stack is reduced by 33% after Ar plasma treatment of the oxide. Besides, the negative photo-conductivity (NPC) effect, normally observed on many locations following electrical soft-breakdown, is suppressed. The NPC effect arises because the electrically-formed filamentary conductive path, comprising both Cu and oxygen vacancies, may be disrupted by the recombination of the vacancies with nearby light-excited interstitial oxygen ions. Increase of the O-H peak, as seen from FT-IR spectroscopy, indicates that surface defects generated by the Ar plasma may have adsorbed water molecules, which in turn act as counter anions (OH?) accelerating Cu-ion diffusion into the oxide, forming a more complete Cu filament that is non-responsive to light. The finding offers the possibility of both electrical and optical resistance control by a simple surface treatment step.
关键词： Ar plasma treatment,negative photo-conductivity,conductive atomic force microscope,resistive switching,SiO2/Cu stack
更新于2025-09-23 15:21:01
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Mapping Local Surface Plasmon Modes in a Nanoplasmonic Trimer Using Cathodoluminescence in the Scanning Electron Microscope
摘要： The excitability of local surface plasmon modes in radial trimers composed of gold nanorods was mapped using hyperspectral cathodoluminescence (CL) in the scanning electron microscope. In symmetric trimers, the local plasmon resonances could be excited most effectively at the ends of individual rods. Introducing asymmetry into the structure breaks the degeneracy of the dipole modes and changes the excitability of transverse dipole modes in different directions. CL in the scanning electron microscope has great potential to interrogate individual nanophotonic structures and is a complement to electron energy loss spectroscopy and optical microscopy.
关键词： scanning electron microscope,local surface plasmon mode,nanoplasmonic trimer,cathodoluminescence
更新于2025-09-23 15:21:01
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Real-time visualization of GaN/AlGaN high electron mobility transistor failure at off-state
摘要： Degradation and failure phenomena in high electron mobility transistors (HEMTs) are complex functions of electrical, thermal, and mechanical stresses as well as the quality of the device materials and their interfaces. Thus, it is difficult to predict or identify the dominant mechanism under various test protocols adopted in the literature. We propose that real-time visualization of the device microstructure can shift this paradigm. This is demonstrated by operating electron transparent AlGaN/GaN HEMTs inside a transmission electron microscope (TEM). Through the bright-field, diffraction, and energy dispersive spectroscopy techniques, we show that it is possible to characterize the lattice defects and diffusion of the various elements and thus monitor the micro-structural quality during the transistor failure. Off-state failure studies in the TEM clearly show the critical role of defects and interfaces that lead to punch-through mechanisms at the drain and even source sides. The 'seeing while measuring' approach presented in this study can be useful in pinpointing the dominant failure mechanisms and their fundamental origin.
关键词： GaN HEMTs,energy dispersive spectroscopy,lattice defects,transmission electron microscope,off-state failure,real-time visualization
更新于2025-09-23 15:21:01
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Tracing Tubular Structures from Teravoxel-Sized Microscope Images
摘要： Tracing vasculature and neurites from teravoxel-sized light-microscopy data-sets is a challenge impeding the availability of processed data to the research community. This is because (1) Holding terabytes of data during run-time is not easy for a regular PC. (2) Processing all the data at once would be slow and inefficient. In this paper, we propose a way to mitigate this challenge by Divide Conquer and Combine (DCC) method. We first split the volume into many smaller and manageable sub-volumes before tracing. These sub-volumes can then be traced individually in parallel (or otherwise). We propose an algorithm to stitch together the traced data from these sub-volumes. This algorithm is robust and handles challenging scenarios like (1) sub-optimal tracing at edges (2) densely packed structures and (3) different depths of trace termination. We validate our results using whole mouse brain vasculature data-set obtained from the Knife-Edge Scanning Microscopy (KESM) based automated tissue scanner.
关键词： Divide Conquer and Combine,Tracing,Neurites,Knife-Edge Scanning Microscopy,Teravoxel-sized,Microscope Images,Vasculature
更新于2025-09-23 15:21:01
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Pulsed interleaved excitation-based line-scanning spatial correlation spectroscopy (PIE-lsSCS)
摘要： We report pulsed interleaved excitation (PIE) based line-scanning spatial correlation spectroscopy (PIE-lsSCS), a quantitative fluorescence microscopy method for the study of dynamics in free-standing lipid bilayer membranes. Using a confocal microscope, we scan multiple lines perpendicularly through the membrane, each one laterally displaced from the previous one by several ten nanometers. Scanning through the membrane enables us to eliminate intensity fluctuations due to membrane displacements with respect to the observation volume. The diffusion of fluorescent molecules within the membrane is quantified by spatial correlation analysis, based on the fixed lag times between successive line scans. PIE affords dual-color excitation within a single line scan and avoids channel crosstalk. PIE-lsSCS data are acquired from a larger membrane region so that sampling is more efficient. Moreover, the local photon flux is reduced compared with single-point experiments, resulting in a smaller fraction of photobleached molecules for identical exposure times. This is helpful for precise measurements on live cells and tissues. We have evaluated the method with experiments on fluorescently labeled giant unilamellar vesicles (GUVs) and membrane-stained live cells.
关键词： lipid bilayer membranes,dual-color excitation,live cells,line-scanning spatial correlation spectroscopy,fluorescence microscopy,tissues,GUVs,confocal microscope,photobleaching,Pulsed interleaved excitation
更新于2025-09-23 15:21:01
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[American Society of Agricultural and Biological Engineers 2017 Spokane, Washington July 16 - July 19, 2017 - ()] 2017 Spokane, Washington July 16 - July 19, 2017 - <i>Rapid and reliable norovirus assay at pg/mL level using smartphone-based fluorescence microscope and a microfluidic paper analytic device</i>
摘要： Detection of norovirus from water samples typically requires extremely low limit of detection (LOD), preferably at single virus particle level, since they can be pathogenic at extremely low concentrations. Complicated equipment and/or lengthy procedures are necessary to concentrate large volume of water sample. In addition, this low LOD requirement have traditionally been associated non-reproducible and less convincing assay results. In this work, rapid and reliable detection of norovirus contamination in water samples was demonstrated using an in-house developed smartphone-based fluorescence microscope and a paper microfluidic analytic device (μPAD). Norovirus was concentrated directly on the μPAD, which was fabricated with polarity filter, to further decrease the LOD. Antibody-conjugated submicron (0.5 μm diameter) fluorescent particles were added to this μPAD, and a smartphone based fluorescence microscope imaged these beads directly from the μPAD. Since the spatial resolution of our smartphone-based fluorescence microscope is > 1 μm, only the beads immunoaggltuinated by norovirus can be identified, providing reliable, reproducible, and visually convincing assay results. Using this novel this method, extremely low LOD was demonstrated, 0.01 pg/mL with a benchtop fluorescence microscope and 10 pg/mL to 100 pg/mL with a smartphone based fluorescence microscope. This novel assay can provide a fully unmanned platform for assaying various waterborne pathogens that require extremely low LOD as well as high reliability, while providing low-cost, ease-of-use, and user friendliness appropriate for field applications.
关键词： μPAD,fluorescence microscope,waterborne pathogen,immunoagglutination,microfluidic device
更新于2025-09-23 15:21:01
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Build Your Own Microscope: Step-By-Step Guide for Building a Prism-Based TIRF Microscope
摘要： Prism-based total internal re?ection ?uorescence (pTIRF) microscopy is one of the most widely used techniques for the single molecule analysis of a vast range of samples including biomolecules, nanostructures, and cells, to name a few. It allows for excitation of surface bound molecules/particles/quantum dots via evanescent ?eld of a con?ned region of space, which is bene?cial not only for single molecule detection but also for analysis of single molecule dynamics and for acquiring kinetics data. However, there is neither a commercial microscope available for purchase nor a detailed guide dedicated for building this microscope. Thus far, pTIRF microscopes are custom-built with the use of a commercially available inverted microscope, which requires high level of expertise in selecting and handling sophisticated instrument-parts. To directly address this technology gap, here we describe a step-by-step guide on how to build and characterize a pTIRF microscope for in vitro single-molecule imaging, nanostructure analysis and other life sciences research.
关键词： single-molecule detection,single-molecule FRET,?uorescence microscope,pTIRF
更新于2025-09-23 15:21:01
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Ultrahigh Resolution Mouse Optical Coherence Tomography to Aid Intraocular Injection in Retinal Gene Therapy Research
摘要： HR-SD-OCT is utilized to monitor the progression of photoreceptor degeneration in live mouse models, assess the delivery of therapeutic agents into the subretinal space, and to evaluate toxicity and efficacy in vivo. HR-SD-OCT uses near infrared light (800-880 nm) and has optics specifically designed for the unique optics of the mouse eye with sub-2-micron axial resolution. Transgenic mouse models of outer retinal (photoreceptor) degeneration and controls were imaged to assess the disease progression. Pulled glass microneedles were used to deliver sub retinal injections of adeno-associated virus (AAV) or nanoparticles (NP) via a trans-scleral and trans-choroidal approach. Careful positioning of the needle into the subretinal space was required prior to a calibrated pressure injection, which delivers fluid into the sub retinal space. Real time subretinal surgery was conducted on our retinal imaging system (RIS). HR-SD-OCT demonstrated progressive uniform retinal degeneration due to expression of a toxic mutant human mutant rhodopsin (P347S) (RHOP347S) transgene in mice. HR-SD-OCT allows rigorous quantification of all the retinal layers. Outer nuclear layer (ONL) thickness and photoreceptor outer segment length (OSL) measurements correlate with photoreceptor vitality, degeneration, or rescue. The RIS delivery system allows real-time visualization of subretinal injections in neonatal (~P10-14) or adult mice, and HR-SD-OCT immediately determines success of delivery and maps areal extent. HR-SD-OCT is a powerful tool that can evaluate the success of subretinal surgery in mice, in addition to measuring vitality of photoreceptors in vivo. HR-SD-OCT can also be used to identify uniform animal cohorts to evaluate the extent of retinal degeneration, toxicity, and therapeutic rescue in preclinical gene therapy research studies.
关键词： Optical Coherence Tomography,Retinal Degeneration,Imaging,Real-time,Retina,Microscope,Intraocular Injection,Preclinical,In Vivo,Photoreceptors,Greenough Stereo Microscopy,Sub-retinal
更新于2025-09-23 15:21:01
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Fabrication of frequency selective metamaterial structure using low-cost laser writer
摘要： Tailoring the metamaterial structure using Laser writer lithography system offers a feasible way to accomplish the fine cross grating structures. The main focus of this work is to fabricate a metamaterial for absorption in the far infrared (far-IR) spectrum. Fabrication was carried out using homemade laser writer working at 405 nm in S1813 photoresist coated upon chromium on glass followed by its etching in the exposed regions. A 40 ? 40 array of unit cells with dimension in the order of 28 μm ? 1 μm were achieved. The structural characterization was carried out using scanning electron microscope (SEM) and Optical Microscope. We could observe clear absorption in the far-IR region. The results here would be favorable for the development of devices based on artificial material whose properties are not readily accessible in nature (metamaterials).
关键词： Optical microscope,FTIR,Laser writer,Metamaterial,SEM
更新于2025-09-23 15:19:57
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Unveiling Complex Plasmonic Resonances in Archimedean Nanospirals through Cathodoluminescence in a Scanning Transmission Electron Microscope
摘要： Metallic nanostructures with a complex plasmonic response, such as the Archimedean nanospiral (ANS) present novel ways to utilize plasmonics in modern technology [1,2]. The nanospiral can support several resonant modes, with distinct electric field profiles as shown by finite-difference time-domain (FDTD) simulations such as the hourglass (500-650nm) and focusing (650-980nm) modes [2]. In addition to the linear plasmonic response, the ANS exhibits a stronger second-order nonlinearity than seen in other metallic nanostructured systems. A high spatial-resolution picture of the plasmonic modes is critical to understanding the interactions between plasmonic modes that drive the high non-linear efficiencies [3]. Purely optical experiments struggle to observe the near field behavior of the structure due to being diffraction limited. However cathodoluminescence (CL) experiments in a scanning transmission electron microscope (STEM) create a unique opportunity for characterizing plasmonic systems with both the spatial sensitivity of electron optics and the spectral sensitivity of photonics. A significant benefit to the use of STEM-CL, as opposed to other high-resolution spectroscopy techniques such as electron energy loss spectroscopy (EELS), is that the photons generated from radiative decays in the sample are collected for signal instead of the electrons from the probe. As a result, the signal can be manipulated and filtered using standard optical techniques, allowing us to map difficult to observe plasmon modes and even give insight into the polarization of their radiative decay. To experimentally observe the plasmon modes, an Au ANS array is fabricated using electron-beam lithography on a 50 nm silicon nitride film supported by a silicon substrate. A 500μm x500 μm window is then backside-etched beneath the array. STEM-CL is done in a VG-HB601 STEM operated at 60 kV with a home-built CL spectrometer system. Radiative emission is collected with a parabolic mirror and reflected out of a port in the side of the microscope, allowing the signal to be filtered and polarized using standard optical equipment, and ultimately collected in a photomultiplier tube (PMT). First, the focusing mode (650-980nm) is examined. Fig 1a shows a FDTD simulation of the plasmon mode. Fig 1b shows a high angle annular dark field (HAADF) image of the fabricated ANS on the SiN window. The raw CL intensity is shown in Fig 1c with no spectral filtering. Emission from all plasmonic modes, interband transitions, and any other radiative decay pathways are all simultaneously detected. However, by spectrally filtering the CL signal, individual modes can be isolated. The focusing mode is predicted to be strongest in the 650-980 nm region, so by using a 600 nm long-pass spectral filter, the radiative decay from other optical features can be eliminated, and a map of the focusing mode (Figure 1d) can be obtained. For the hourglass mode, however, spectral filters cannot be used to observe the spatial profile of the plasmonic resonance, because unlike the focusing mode, the hourglass mode has a distinct polarization axis that is parallel to the axis of the exciting optical pulse, as shown in the FDTD simulation in Fig 1e. With no polarization selectivity on electron-optics, the hourglass plasmon modes can be excited in all in-plane axes of the ANS simultaneously within the STEM, and no individual plasmon can be isolated and detected. However, since the hourglass mode has a strong polarization dependence on the exciting pulse, it is likely that the resulting emission is similarly polarized. In Fig 1f the HAADF image of an ANS is shown, and Fig 1g shows the unfiltered CL image. Fig 1h shows CL image filtered with a linear polarizer and exhibits a similar spatial profile to the simulation in Fig 1e, demonstrating that the modes that have a have a strong dependence on the polarization of the exciting optical source also exhibit a polarization dependence on their radiative decay. Nanostructures with complex, nonlinear plasmonic responses, such as the ANS, have unique optical attributes not present in simpler geometries. As a result, high spatial-resolution techniques to investigate the near-field profiles are an important avenue of plasmonic investigation. STEM-CL presents a particularly unique opportunity to combine photon and electron optics in order to characterize and map plasmonic modes, such as the hourglass and focusing modes of the ANS, with nanoscale precision.
关键词： nonlinearity,cathodoluminescence,scanning transmission electron microscope,Archimedean nanospiral,plasmonics
更新于2025-09-23 15:19:57