A5057316681- Nanowire Synthesis and Applications
- solar cell performance optimization
- Neurobiology and Insect Physiology Research
- Thin-Film Transistor Technologies
- Semiconductor materials and interfaces
- Semiconductor Quantum Structures and Devices
- Silicon and Solar Cell Technologies
- Advancements in Semiconductor Devices and Circuit Design
- GaN-based semiconductor devices and materials
- Insect and Arachnid Ecology and Behavior
- Neural dynamics and brain function
- Olfactory and Sensory Function Studies
- Photoreceptor and optogenetics research
- Quantum Dots Synthesis And Properties
- Electronic and Structural Properties of Oxides
- Plant and Biological Electrophysiology Studies
- Memory and Neural Mechanisms
- Animal Behavior and Reproduction
- Chalcogenide Semiconductor Thin Films
- Circadian rhythm and melatonin
- Cellular transport and secretion
- Neuroscience and Neural Engineering
- Sphingolipid Metabolism and Signaling
- Ga2O3 and related materials
- Molecular Junctions and Nanostructures
University of California, Santa Cruz
2023-2024
Santa Cruz County Office of Education
2023
Howard Hughes Medical Institute
2016-2021
Janelia Research Campus
2016-2021
Helix (United States)
2016
California Institute of Technology
2008-2015
Yale University
2005-2007
University of New Haven
2006
City College of New York
2006
State Street (United States)
2006
Arrays of B-doped p-Si microwires, diffusion-doped with P to form a radial n+ emitter and subsequently coated 1.5-nm-thick discontinuous film evaporated Pt, were used as photocathodes for H2 evolution from water. These electrodes yielded thermodynamically based energy-conversion efficiencies >5% under 1 sun solar simulation, despite absorbing less than 50% the above-band-gap incident photons. Analogous wire-array <0.2%, largely limited by low photovoltage generated at p-Si/H2O junction.
Single-nanowire solar cells were created by forming rectifying junctions in electrically contacted vapor-liquid-solid-grown Si nanowires. The nanowires had diameters the range of 200 nm to 1.5 microm. Dark and light current-voltage measurements made under simulated Air Mass global illumination. Photovoltaic spectral response also performed. Scanning photocurrent microscopy indicated that nanowire devices minority carrier diffusion lengths approximately 2 Assuming bulk-dominated...
Silicon wire arrays, though attractive materials for use in photovoltaics and as photocathodes hydrogen generation, have to date exhibited poor performance. Using a copper-catalyzed, vapor-liquid-solid-growth process, SiCl4 BCl3 were used grow ordered arrays of crystalline p-type silicon (p-Si) microwires on p+-Si(111) substrates. When these contact with an aqueous methyl viologen(2+/+) electrolyte, energy-conversion efficiencies up 3% observed monochromatic 808-nanometer light at fluxes...
Flexible behaviors over long timescales are thought to engage recurrent neural networks in deep brain regions, which experimentally challenging study. In insects, circuit dynamics a region called the central complex (CX) enable directed locomotion, sleep, and context- experience-dependent spatial navigation. We describe first complete electron microscopy-based connectome of
Many animals maintain an internal representation of their heading as they move through surroundings. Such a compass was recently discovered in neural population the Drosophila melanogaster central complex, brain region implicated spatial navigation. Here, we use two-photon calcium imaging and electrophysiology head-fixed walking flies to identify different that conjunctively encodes angular velocity, is excited selectively by turns either clockwise or counterclockwise direction. We show how...
Si microwire-array solar cells with Air Mass 1.5 Global conversion efficiencies of up to 7.9% have been fabricated using an active volume equivalent a 4 μm thick wafer. These exhibited open-circuit voltages 500 mV, short-circuit current densities (Jsc) 24 mA cm-2, and fill factors >65% employed Al2O3 dielectric particles that scattered light incident in the space between wires, Ag back reflector prevented escape illumination from surface cell, a-SiNx:H passivation/anti-reflection layer....
Crystalline Si wires, grown by the vapor–liquid–solid (VLS) process, have emerged as promising candidate materials for low-cost, thin-film photovoltaics. Here, we demonstrate VLS-grown microwires that suitable electrical properties high-performance photovoltaic applications, including long minority-carrier diffusion lengths (Ln ≫ 30 µm) and low surface recombination velocities (S ≪ 70 cm·s−1). Single-wire radial p–n junction solar cells were fabricated with amorphous silicon nitride...
ABSTRACT Flexible behaviors over long timescales are thought to engage recurrent neural networks in deep brain regions, which experimentally challenging study. In insects, circuit dynamics a region called the central complex (CX) enable directed locomotion, sleep, and context- experience-dependent spatial navigation. We describe first complete electron-microscopy-based connectome of Drosophila CX, including all its neurons circuits at synaptic resolution. identified new CX neuron types,...
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...
The effective electron minority-carrier diffusion length, Ln,eff, for 2.0 μm diameter Si wires that were synthesized by Cu-catalyzed vapor-liquid-solid growth was measured scanning photocurrent microscopy. In dark, ambient conditions, Ln,eff limited surface recombination to a value of ≤0.7 μm. However, Ln,eff=10.5±1 under broad-area illumination in low-level injection. relatively long length observed is consistent with an increased passivation resulting from filling the states photogenerated...
Solar cells based on arrays of CVD-grown Si nano- or micro-wires have attracted interest as potentially low-cost alternatives to conventional wafer-based photovoltaics [1-6], and single-wire solar been reported with efficiencies up 3.4% [7]. We recently presented device physics simulations which predicted exceeding 17%, experimentally observed diffusion lengths within our wires [8]. However, this model did not take into account the optical properties a wire array - in particular inherently...
Abstract Gallium phosphide exhibits a short diffusion length relative to its optical absorption length, and is thus candidate for use in wire array geometries that allow light be decoupled from minority carrier collection. Herein reported the photoanodic performance of heteroepitaxially grown gallium on planar microwire‐array Si substrates. The n‐GaP|n‐Si heterojunction results favorable conduction band alignment electron collection silicon. A conformal electrochemical contact outer GaP...
Seizures induced by visual stimulation (photosensitive epilepsy; PSE) represent a common type of epilepsy in humans, but the molecular mechanisms and genetic drivers underlying PSE remain unknown, no good animal models have been identified as yet. Here, we show an model PSE, Drosophila, owing to defective cortex glia. The glial membranes are severely compromised ceramide phosphoethanolamine synthase (cpes)-null mutants fail encapsulate neuronal cell bodies Drosophila cortex. Expression human...
Abstract Navigating animals continuously integrate velocity signals to update internal representations of their directional heading and spatial location in the environment. How neural circuits combine sensory motor information construct these estimates how self-motion signals, turn, that support navigational computations are not well understood. Recent work Drosophila has identified a circuit performs angular path integration compute fly’s head direction, but nature signal is unknown. Here...
Indium nitride nanowires (NWs) grown by a catalyst-free, vapor-solid method are shown to be high-purity, single-crystal hexagonal wurtzite and intrinsic n type with uniform diameters that range from 70to150nm lengths vary between 3 30μm. Single NWs were fabricated into field-effect transistors the electronic material parameters of wires extracted found identical comparable bulk InN.
A comparison of methods to create Ohmic contacts semiconductor nanowires (NWs) and carbon nanotubes (CNTs) is presented. Ni∕Au lift-off metallization was used contact GaN In2O3 NWs CNTs using electron-beam (e-beam) or optical lithography. In order render the metal-semiconductor Ohmic, e-beam-processed devices are found require a postfabrication, high-temperature anneal, whereas use an oxygen plasma prior be crucial for defined by
ABSTRACT Neural representations of head direction have been discovered in many species. A large body theoretical work has proposed that the dynamics associated with these is generated, maintained, and updated by recurrent network structures called ring attractors. We performed electron microscopy-based circuit reconstruction RNA profiling identified cell types heading system Drosophila melanogaster to directly determine underlying neural network. motifs hypothesized maintain representation...
Solar cells based on arrays of CVD-grown Si nano- or micro-wires are being considered as a potentially low-cost route to implementing vertical multijunction cell design via radial p-n junctions. This geometry has been predicted enable efficiencies competitive with planar multicrystalline designs, while reducing the materials and processing costs solar fabrication [1]. To further assess potential efficiency this design, we present here experimental measurements minority carrier diffusion...
A critical shortcoming of current surface functionalization schemes is their inability to selectively coat patterned substrates at micrometer and nanometer scales. This limitation prevents localized deposition macromolecules high densities, thereby restricting the versatility surface. new approach for functionalizing lithographically that eliminates need alignment and, thus, scalable any dimension reported. We show, first time, electropolymerization derivatized phenols can functionalize...
Silicon microwire arrays have recently demonstrated their potential for low-cost, high-efficiency photovoltaics and photoelectrochemical fuel generation. A remaining challenge to making this technology commercially viable is scaling up of microwire-array growth. We discuss here a technique vapor–liquid–solid growth on the scale six-inch wafers using cold-wall radio-frequency heated chemical vapor deposition furnace, enabling fairly uniform over large areas with rapid cycle time improved...