A5020660167- GaN-based semiconductor devices and materials
- Nanowire Synthesis and Applications
- Ga2O3 and related materials
- ZnO doping and properties
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Silicon and Solar Cell Technologies
- Semiconductor Quantum Structures and Devices
- Force Microscopy Techniques and Applications
- Microwave and Dielectric Measurement Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- Power Line Communications and Noise
- Radio Frequency Integrated Circuit Design
- Thin-Film Transistor Technologies
- Carbon Nanotubes in Composites
- Electron and X-Ray Spectroscopy Techniques
- Mechanical and Optical Resonators
- Advanced Electron Microscopy Techniques and Applications
- Advanced MIMO Systems Optimization
- Photonic and Optical Devices
- Nanoparticles: synthesis and applications
- Advanced Electrical Measurement Techniques
- Nuclear Physics and Applications
- Silicon Nanostructures and Photoluminescence
- Near-Field Optical Microscopy
University of Arkansas – Fort Smith
2025
National Institute of Standards and Technology
2013-2024
Communications Technology Laboratory
2019-2024
University of Colorado Boulder
2015-2022
National Institute of Standards
2009-2022
Thomas Jefferson National Accelerator Facility
2021
Yale University
2005-2019
University of North Texas
1999-2019
Saint Petersburg State Electrotechnical University
2019
Czech Technical University in Prague
2019
We report the coupling of free-space photons (vacuum wavelength 830 nm) to surface plasmon modes a silver nanowire. The launch propagating plasmons, and subsequent emission photons, is selective occurs only at ends other discontinuities In addition, we observe that nanowires redirect plasmons through turns radii as small 4 μm. exploit radiating nature find propagation length >3 ± 1 Finally, interwire for overlapping wires, demonstrating fan-out subwavelength scales.
Protein folding occurs as a set of transitions between structural states within an energy landscape. An oversimplified view the process emerges when transiently populated are undetected because limited instrumental resolution. Using force spectroscopy optimized for 1-microsecond resolution, we reexamined unfolding individual bacteriorhodopsin molecules in native lipid bilayers. The experimental data reveal pathway unprecedented detail. Numerous newly detected intermediates-many separated by...
We report a novel strategy for the controlled synthesis of gold nanoparticles (AuNPs) with narrow size distribution (1.9 ± 0.4 nm) through NP nucleation and growth inside cavity well-defined three-dimensional, shape-persistent organic molecular cage. Our results show that both cage structure pendant thioether groups pointing are essential AuNP synthesis.
Vertically aligned multiwall carbon nanotubes were grown by water-assisted chemical vapor deposition on a large-area lithium tantalate pyroelectric detector. The processing parameters are nominally identical to those which others have achieved the "world's darkest substance" silicon substrate. detector material, though good candidate for such coating, presents additional challenges and outcomes. After cycle of heating, electric field poling, cooling was employed restore spontaneous...
Abstract The location of GaN nanowires is controlled with essentially perfect selectivity using patterned SiN x prior to molecular beam epitaxy growth. Nanowire growth uniform within mask openings and absent on the surface for over 95% usable area a 76 mm diameter substrate. diameters resulting are by size openings. Openings approximately 500 nm or less produce single symmetrically faceted tips.
Analysis of steady-state and transient photoconductivity measurements at room temperature performed on c-axis oriented GaN nanowires yielded estimates free carrier concentration, drift mobility, surface band bending, capture coefficient for electrons. Samples grown (unintentionally n-type) by nitrogen-plasma-assisted molecular beam epitaxy primarily from two separate growth runs were examined. The results revealed concentration in the range (3–6)×1016 cm−3 one run, roughly 5×1014–1×1015...
In this Letter we report on the fabrication, device characteristics, and optical coupling of a two-nanowire comprising GaN nanowires with light-emitting photoconductive capabilities. Axial p-n junction were grown by molecular beam epitaxy, transferred to non-native substrate, selectively contacted form discrete source or detector nanowire components. The demonstrated for may provide new opportunities integration interconnects between on-chip electrical subsystems.
Biomass exhibits a complex microstructure of directional pores that impact how heat and mass are transferred within biomass particles during conversion processes. However, models used in simulations processes typically employ oversimplified geometries such as spheres cylinders neglect intraparticle microstructure. Here we develop 3D with size, morphology, based on parameters obtained from quantitative image analysis. We obtain measurements particle size morphology by analyzing large...
We have demonstrated dramatic improvement in the quality of selective-area GaN nanowire growth by controlling polarity underlying nucleation layers. In particular, we find that N-polarity is beneficial for large ordered arrays with arbitrary spacing. Herein, present techniques obtaining and characterizing polarity-controlled layers on Si (111) substrates. An initial AlN layer, which to adopt Al- (N-)polarity N- (Al-)rich conditions, utilized configure subsequently grown as determined...
In this paper a statistically significant study of 1096 individual GaN nanowire (NW) devices is presented. We have correlated the effects changing growth parameters for hot-wall chemically-vapour-deposited (HW-CVD) NWs fabricated via vapour–liquid–solid mechanism. first describe an optical lithographic method creating Ohmic contacts to NW field effect transistors with both top and bottom electrostatic gates characterize carrier density mobility. Multiprobe measurements show that modulation...
Advances in genetic manipulation of the biopolymers that compose plant cell walls will facilitate more efficient production biofuels and chemicals from biomass lead to specialized biomaterials with tailored properties. Here we investigate several variants Arabidopsis: wild type, which makes a lignin polymer primarily guaiacyl (G) syringyl (S) monomeric units, fah1 mutant, almost exclusively G subunits, ferulate 5-hydroxylase (F5H) overexpressing line (C4H:F5H) S subunits. We employ...
Atomic force microscopy (AFM)-based single-molecule spectroscopy (SMFS) is widely used to mechanically measure the folding and unfolding of proteins. However, temporal resolution a standard commercial cantilever 50-1000 μs, masking rapid transitions short-lived intermediates. Recently, SMFS with 0.7-μs was achieved using an ultrashort (L = 9 μm) on custom-built, high-speed AFM. By micromachining such cantilevers focused ion beam, we optimized them for rather than tapping-mode imaging. To...
One of the fundamental endeavors in radio frequency (RF) metrology is to measure power signals, where a common aim estimate peak-to-average ratio (PAPR), which quantifies maximum (peak) mean value. For finite number discrete-time samples baseband in-phase and quadrature (I/Q) white Gaussian noise (WGN) that are independent identically distributed with zero mean, we derive closed-form, exact formula for PAPR well-approximated by natural logarithm plus Euler's constant. Additionally, give...
Organic electrochemical transistors (OECTs) represent a promising platform for biosensing applications in aqueous environments, including the sensitive detection of neurotransmitter molecules, such as serotonin (SE). Conventional methods SE detection, HPLC and ELISA, are time-consuming expensive. Electrochemical sensors, while cost-effective, often struggle with real-time selectivity issues due to interference from similar biomolecules, dopamine (DA), ascorbic acid (AA), uric (UA). These...
In this paper, we demonstrate novel MESFETs based on individual GaN nanowires. The Pt/Au Schottky gates exhibited excellent two-terminal diode rectification behavior. average effective barrier height was 0.87 eV, with an ideality factor of 1.6. addition, the efficiently modulated conduction threshold gate voltages required for complete pinch off were as small -2.6 V, and transconductances exceeded 1.4 muS. Subthreshold swings approaching 60 mV/decade on/off current ratios up to 5times10 <sup...
Formulations and applications of micro- nanoscale polymer particles have proliferated rapidly in recent years, yet knowledge their mechanical behavior has not grown accordingly. In this study, we examine the ways that compressive strain, substrate surface energy, particle size influence shape memory cycle polystyrene particles. Using nanoimprint lithography, differently sized are programmed into highly deformed, temporary shapes contact with substrates differing energies. Atomic force...
We measure the J = 1 to 2 fine structure interval in ( 3)2P state of helium be 291 175.9(1.0) kHz. use laser excitation an atomic beam along with integrated electro-optic modulator technique obtain this result. The result is consistent (2.9+/-3.2 kHz) what could considered earlier version experiment but not good agreement 20+/-5 kHz and 22+/-8 two other precision determinations interval. current theoretical prediction lies between overlaps experiments.
Theory and measurements of the conductivity (transient) photoconductivity in microwave frequency range are presented. The theory is tested on noninvasive semiconductors with known properties, i.e., Si wafers, a simple apparatus. Quantitative agreement between experiment found without use adjustable parameters. A contactless accurate determination wafers restricted proposed. quantitative evaluation makes detailed discussion nonuniform possible. requirements for reliable nonhomogeneous charge...
Using liquid crystalline self-assembly of cellulose nanocrystals, we achieve long-range alignment anisotropic metal nanoparticles in colloidal nanocrystal dispersions that are then used to deposit thin structured films with ordering features highly dependent on the deposition method. These hybrid comprised gold nanorods unidirectionally aligned a matrix can be made ordered nanocrystals or silica nanostructures obtained by using cellulose-based as replica. The ensuing both and nanoporous...
Variable intensity photoconductivity (PC) performed under vacuum at 325 nm was used to estimate drift mobility (μ) and density (σs) of negative surface charge for c-axis oriented Si-doped GaN nanowires (NWs). In this approach, we assumed that σs responsible the equilibrium band bending (∅) depletion in absence illumination. The NWs were grown by molecular beam epitaxy a length approximately 10 μm exhibited negligible taper. free carrier concentration (N) separately measured using Raman...
Contactless transient photoconductivity measurements are used to study excess charge carrier transport in single-crystal silicon wafers. It is shown that the minority diffusion constant and lifetime can be determined from decay behaviour by varying thickness of wafer. The presence non-uniform defect densities studied their influence on carriers. This demonstrated investigation a proton-irradiated wafer after an internal gettering treatmen.
Analysis of the Josephson junction yield in National Institute Standards and Technology 10 V Programmable Voltage Standard (PJVS) has been performed by fabricating measuring over 25 million Nb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Si xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> /Nb junctions. Using 265 116 junctions per PJVS device, it was possible to measure Shapiro steps on current voltage curves then estimate...