A5037166357- Carbon Nanotubes in Composites
- Graphene research and applications
- Thermal properties of materials
- Advanced Thermoelectric Materials and Devices
- Nanowire Synthesis and Applications
- 2D Materials and Applications
- Mechanical and Optical Resonators
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced Photocatalysis Techniques
- Quantum Dots Synthesis And Properties
- Thermal Radiation and Cooling Technologies
- Plasmonic and Surface Plasmon Research
- Quantum and electron transport phenomena
- Diamond and Carbon-based Materials Research
- Semiconductor materials and devices
- Chalcogenide Semiconductor Thin Films
- Catalytic Processes in Materials Science
- Semiconductor materials and interfaces
- Anodic Oxide Films and Nanostructures
- MXene and MAX Phase Materials
- Perovskite Materials and Applications
- Surface and Thin Film Phenomena
- Electrochemical Analysis and Applications
- Nanopore and Nanochannel Transport Studies
- Boron and Carbon Nanomaterials Research
University of Southern California
2016-2025
Southern California University for Professional Studies
2014-2025
Minghsin University of Science and Technology
2018-2022
Transient Plasma Systems (United States)
2020-2021
Los Angeles City College
2017-2018
California NanoSystems Institute
2015
University of California, Los Angeles
2015
California Institute of Technology
2007-2013
Joint Center for Artificial Photosynthesis
2013
The University of Texas at Austin
2009
We demonstrate plasmonic enhancement of photocatalytic water splitting under visible illumination by integrating strongly Au nanoparticles with catalytic TiO2. Under illumination, we observe enhancements up to 66× in the TiO2 addition nanoparticles. Above plasmon resonance, ultraviolet radiation a 4-fold reduction activity. Electromagnetic simulations indicate that improvement activity range is caused local electric field near surface, rather than direct transfer charge between two...
A systematic study of the mechanisms Au nanoparticle/TiO2-catalyzed photoreduction CO2 and water vapor is carried out over a wide range wavelengths. When photon energy matches plasmon resonance nanoparticles (free carrier absorption), which in visible (532 nm), we observe 24-fold enhancement photocatalytic activity because intense local electromagnetic fields created by surface plasmons nanoparticles. These enhance sub-bandgap absorption TiO2, thereby enhancing range. high enough to excite d...
We have fabricated graphene-silicon Schottky diodes by depositing mechanically exfoliated graphene on top of silicon substrates. The resulting current-voltage characteristics exhibit rectifying diode behavior with a barrier energy 0.41 eV n-type and 0.45 p-type at the room temperature. I-V measured 100, 300, 400 K indicate that temperature strongly influences ideality factor diodes. factor, however, does not depend number layers. optical transparency thin layer allows underlying substrate to...
New layered anisotropic infrared semiconductors, black arsenic-phosphorus (b-AsP), with highly tunable chemical compositions and electronic optical properties are introduced. Transport absorption studies demonstrate the semiconducting nature of b-AsP bandgaps, ranging from 0.3 to 0.15 eV. These bandgaps fall into long-wavelength regime cannot be readily reached by other materials.
Modern microelectronic devices have nanoscale features that dissipate power nonuniformly, but fundamental physical limits frustrate efforts to detect the resulting temperature gradients. Contact thermometers disturb of a small system, while radiation struggle beat diffraction limit. Exploiting same physics as Fahrenheit's glass-bulb thermometer, we mapped thermal expansion Joule-heated, 80-nanometer-thick aluminum wires by precisely measuring changes in density. With scanning transmission...
Abstract The morphology and dimension of the conductive filament formed in a memristive device are strongly influenced by thickness its switching medium layer. Aggressive scaling this active layer is critical toward reducing operating current, voltage, energy consumption filamentary‐type memristors. Previously, has been limited to above few nanometers due processing constraints, making it challenging further suppress on‐state current voltage. Here, formation filaments material with...
This paper reports galvanomagnetic properties of arrays single-crystal bismuth nanowires, with diameters 7 to 200 nm, embedded in an amorphous porous anodic alumina matrix. A sample preparation technique is described that makes it possible obtain nanowires below 10 nm. The wires are single crystals, their long axes oriented the bisectrix/trigonal plane, about 19\ifmmode^\circ\else\textdegree\fi{} from bisectrix axis. temperature dependence $(1.4\mathrm{K}<~T<~300\mathrm{K})$ electrical...
We demonstrate a method for fabricating arrays of plasmonic nanoparticles with separations on the order 1 nm using an angle evaporation technique. Samples fabricated thin SiN membranes are imaged high-resolution transmission electron microscopy (HRTEM) to resolve small achieved between nanoparticles. When irradiated laser light, these nearly touching metal produce extremely high electric field intensities, which result in surface-enhanced Raman spectroscopy (SERS) signals. quantify...
Abstract A method for the fabrication of thick films porous anodic alumina on rigid substrates is described. The film was generated by anodization an aluminum evaporated substrate. morphology barrier layer between and substrate different from that grown substrates. removal electrochemical growth nanowires within ordered pores were accomplished without need to remove We fabricated samples over large areas (up 70 cm 2 ), deposited in them nanowire arrays various materials. Long obtained with...
Raman spectroscopy is used to measure the strain in individual single-wall carbon nanotubes, strained by manipulation with an atomic-force-microscope tip. Under strains varying from 0.06%-1.65%, in-plane vibrational mode frequencies are lowered as much 1.5% (40 cm(-1)), while radial breathing (RBM) remains unchanged. The RBM Stokes/anti-Stokes intensity ratio unchanged under strain. elasticity of these deformations demonstrated down-shifted modes resume their prestrain after a nanotube...
We report a systematic study of carrier dynamics in AlxGa1–xAs-passivated GaAs nanowires. With passivation, the minority diffusion length (Ldiff) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and photoluminescence (PL) lifetime sub-60 ps 1.3 ns. A 48-fold enhancement continuous-wave PL intensity is observed on same individual nanowire with without AlxGa1–xAs passivation layer, indicating significant reduction surface recombination. These results...
Uniaxial strain is induced by pushing single-wall carbon nanotubes (SWNTs) with an atomic force microscope tip. The vibrational and electronic energies of are found to be very sensitive strain. For both metallic semiconducting SWNTs under strain, the $D$, $G$, ${G}^{\ensuremath{'}}$ band Raman modes downshifted up 27, 15, $40\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, respectively. relative strain-induced shifts bands vary significantly from nanotube nanotube, implying that...
Irradiating gold nanoparticles at their plasmon resonance frequency creates immense plasmonic charge and high temperatures, which can be used to drive catalytic reactions. By integrating strongly with metal oxides, significant enhancements in the activity achieved. Here, we study plasmonically driven conversion of CO CO2 by irradiating Au nanoparticle/Fe2O3 composites. The reaction rate this composite greatly exceeds that or Fe2O3 alone, indicating is not solely thermal (plasmonic) heating...
In the past, electrochemical instability of III–V semiconductors has severely limited their applicability in photocatlaysis. As a result, vast majority research on photocatalysis been done TiO2, which is chemically robust over wide range pH. However, TiO2 band gap (3.2 eV) and can only absorb ∼4% solar spectrum, thus, it will never provide efficient energy conversion/storage its own. Here, we report photocatalytic CO2 reduction with water to produce methanol using TiO2-passivated GaP...
Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates monolithic integration of cell materials that not lattice-matched. Here, we report first realization nanowire-on-Si tandem with observation voltage addition GaAs nanowire top Si bottom an open circuit 0.956 V efficiency 11.4%. Our simulation showed...
We report a robust method for engineering the optoelectronic properties of many-layer MoS2 using low-energy oxygen plasma treatment. Gas phase treatment with radicals generated in an upstream N2 -O2 is shown to enhance photoluminescence (PL) many-layer, mechanically exfoliated flakes by up 20 times, without reducing layer thickness material. A blueshift PL spectra and narrowing linewidth are consistent transition from indirect direct bandgap Atomic force microscopy Raman reveal that flake...