A5015116249- Advanced Optical Imaging Technologies
- Virtual Reality Applications and Impacts
- Plasmonic and Surface Plasmon Research
- 2D Materials and Applications
- Near-Field Optical Microscopy
- Graphene research and applications
- Visual perception and processing mechanisms
- Nanowire Synthesis and Applications
- Force Microscopy Techniques and Applications
- Augmented Reality Applications
- Perovskite Materials and Applications
- Advanced Fluorescence Microscopy Techniques
- Gold and Silver Nanoparticles Synthesis and Applications
- Digital Holography and Microscopy
- Diamond and Carbon-based Materials Research
- Image and Video Quality Assessment
- Chalcogenide Semiconductor Thin Films
- Digital Radiography and Breast Imaging
- Quantum Dots Synthesis And Properties
- Mechanical and Optical Resonators
- Integrated Circuits and Semiconductor Failure Analysis
- Ophthalmology and Visual Impairment Studies
- Carbon Nanotubes in Composites
- Infrared Target Detection Methodologies
- Spectroscopy Techniques in Biomedical and Chemical Research
Center for Devices and Radiological Health
2019-2024
United States Food and Drug Administration
2020-2024
Office of Science
2022-2024
Material Measurement Laboratory
2015-2021
National Institute of Standards and Technology
2015-2021
Food and Drug Administration
2019
University of Rochester
2008-2015
National Institute of Standards
2015
Universidade Federal de Minas Gerais
2010
Argonne National Laboratory
2005
In this article we review Raman studies of defects and dopants in graphene as well the importance both for device applications. First a brief overview spectroscopy is presented. following section discuss characterization three defect types: point defects, edges, grain boundaries. The next reviews dependence spectrum on highlights several common doping techniques. final section, applications are discussed which exploit graphene. Generally degrade figures merit devices, such carrier mobility...
We introduce a simple criterion to identify two-dimensional (2D) materials based on the comparison between experimental lattice constants and mainly obtained from Materials-Project (MP) density functional theory (DFT) calculation repository. Specifically, if relative difference two for specific material is greater than or equal 5%, we predict them be good candidates 2D materials. have predicted at least 1356 such For all systems satisfying our criterion, manually create single layer...
We study the crystal symmetry of few-layer 1T' MoTe2 using polarization dependence second harmonic generation (SHG) and Raman scattering. Bulk is known to be inversion symmetric; however, we find that broken for finite crystals with even numbers layers, resulting in strong SHG comparable other transition-metal dichalcogenides. Group theory analysis signals allows definitive assignment all modes clears up a discrepancy literature. The results were also compared density functional simulations...
We report the results of a new Rosenbluth measurement proton electromagnetic form factors at Q2 values 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting recoiling proton, in contrast to previous measurements which detected scattered electron. 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was 4%-8% showed approximately 1. These are consistent with, much more precise than, extractions. They inconsistent recent polarization transfer similar precision,...
With a template-stripping fabrication technique, we demonstrate the mass of high-quality, uniform, ultrasharp (10 nm) metallic probes suitable for single-molecule fluorescence imaging, tip-enhanced Raman spectroscopy (TERS), and other near-field imaging techniques. We achieve reproducible with sub-20-nm spatial resolution an enhancement in detected signal up to 200. Similar results are obtained TERS carbon nanotubes. show that large apex angle (70.5°) our pyramidal tip is well suited scatter...
Abstract Augmented and virtual reality devices are being actively investigated implemented for a wide range of medical uses. However, significant gaps in the evaluation these applications hinder their regulatory evaluation. Addressing is critical to demonstrating devices’ safety effectiveness. We outline key technical clinical challenges discussed during US Food Drug Administration’s public workshop, “Medical Extended Reality: Toward Best Evaluation Practices Virtual Reality Medicine” future...
Solid-state quantum emitters, such as artificially engineered dots or naturally occurring defects in solids, are being investigated for applications ranging from information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied the perspective of nanoscale metrology. In this letter, we study near-field optical properties a diamond nanocrystal hosting single nitrogen vacancy center. We find that center is sensitive probe surrounding...
We developed a novel optical defocusing method for studying spatial coherence of photoexcited electrons and holes near edges graphene. Our is applied to measure the localization l(D) disorder-induced Raman D band (∼1350 cm(-1)) with resolution few nanometers. scattering experiments performed in helium bath cryostat reveal that as temperature decreased from 300 1.55 K, length increases. found varies 1/T(1/2), giving strong evidence scales graphene edges.
High volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultra-thin films will require deposition techniques that are capable reproducible wafer-scale growth with monolayer control. To date, TMD efforts have largely relied upon sublimation and transport solid precursors minimal control over vapor phase flux gas-phase chemistry, which critical for scaling up laboratory processes to settings. address these issues, we report a new pulsed metalorganic chemical (MOCVD)...
The continually increasing demands for higher-speed and lower-operating-power devices have resulted in the continued impetus to shrink photonic components. We demonstrate a primitive nanophotonic integrated circuit element composed of single silver nanowire single-layer molybdenum disulfide (MoS2) flake. Using scanning confocal fluorescence microscopy spectroscopy, we find that plasmons can excite MoS2 photoluminescence excitons decay into plasmons. Finally, show may serve dual purpose both...
Inelastic light scattering in crystals has historically been treated as a spatially incoherent process, giving rise to optical radiation. Here we demonstrate that Raman can be coherent, which case it depends on the dimensionality and symmetry of scatterer. Using near-field spectroscopy, measure correlation length ∼30 nm for phonons graphene, results varying with vibrational symmetries spatial confinement phonons.
We demonstrate local strain measurements in graphene by using tip-enhanced Raman spectroscopy (TERS). find that a single 5 nm particle can induce radial over lateral distance of ∼170 nm. By treating the as point force on circular membrane, we direction (r) is ∝ r−(2 3),in agreement with force-displacement conducted suspended flakes. Our results TERS be used to map out static fields at nanoscale, which are inaccessible techniques.
The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe2 crystallizes the 2H semiconducting phase at ambient temperature and pressure, but transitions into 1T' semimetallic high temperatures. Alloying with WTe2 reduces energy barrier between these two phases, while also allowing access to Td Weyl semimetal phase. WxTe2 alloy system is therefore promising change memory technology. However,...
A theory describing the near-field Raman enhancement in two-dimensional (2D) systems is presented. The analysis quantifies intensity as a function of tip-sample distance, polarizability tensor components, incident laser beam configuration, and tip orientation relative to sample plane. Our results show that inversely proportional 10th 8th power distance incoherent coherent scattering regimes, respectively. Optimal conditions for inclination angle different configurations are determined, can...
Optical antennas made of gold nanoparticles are used to enhance the spectroscopic response single molecules. With a scannable optical half-wave antenna in form nanorod we achieve spatial resolution 20nm fluorescence imaging. We explore simultaneous and Raman enhancement dye molecules junction two find similar enhancements as function interparticle distance for both scattering. compare our results with theoretical predictions provide possible explanations.
The determination to develop fast, efficient devices has led vast studies on photonic circuits but it is difficult shrink these below the diffraction limit of light. However, coupling between surface plasmon polaritons and nanostructures in near-field shows promise developing next-generation integrated circuitry. In this work, we demonstrate potential for integrating nanoplasmonic-based light guides with atomically thin materials on-chip detection. Specifically, show electrical detection...
Polymer composite materials are found throughout the world both natural and artificial in origin. In vast majority of applications these arenas, composites serve as structural support or reinforcement. Demand for lightweight tough is growing multiple application spaces such aerospace, biomaterials, infrastructure with physical properties diverse applications. The unifying component all presence interphase. Many measurement techniques tools have been developed study this crucial region...
This paper reports the experimental determination of phase-breaking length L conduction electrons in graphene using Raman spectroscopy. Based on double-resonance model, we extract from spatial dependence D band susceptibility near edge. By prior knowledge sample properties and excitation point-spread function are able to determine variation susceptibilities with high accuracy, results reveal a L~40nm
We report on the integration of an individual, metal-based, plasmonic nano-antenna a graphene photodetector. The device exhibits electromagnetic resonance at wavelength 580 nm with well-defined polarization sensitivity. With no applied bias voltage, this antenna-coupled photodetector features responsivity ∼17 nA/μW, which is four orders magnitude higher than previously studied single antenna enhanced detectors. Finally, we measure signal-to-noise ratio ∼200 in 1-Hz bandwidth, average...
A theoretical study describing the coherence properties of near-field Raman scattering in two- and one-dimensional systems is presented. The model applied to modes pristine graphene edges. Our analysis based on tip-enhanced scheme, which a sharp metal tip located near sample surface acts as broadband optical antenna that transfers information contained spatially correlated (but nonpropagating) field far field. dependence scattered signal tip-sample separation explored, theory predicts...
In several recent studies, antenna-based optical microscopy has demonstrated its potential to resolve features as small 10 nm. Most studies are concerned with well-separated on flat surfaces, and there only few that deal samples of high feature density or even three-dimesional objects. The reason is the external laser irradiation antenna (e.g., tip particle) also directly irradiates sample therefore gives rise a background. Here we introduce an efficient background suppression scheme makes...