A5006347592- Graphene research and applications
- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- 2D Materials and Applications
- Boron and Carbon Nanomaterials Research
- Advanced Condensed Matter Physics
- MXene and MAX Phase Materials
- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Advancements in Semiconductor Devices and Circuit Design
- Diamond and Carbon-based Materials Research
- Semiconductor materials and interfaces
- Carbon Nanotubes in Composites
- Thermal properties of materials
- Advanced Thermoelectric Materials and Devices
- Perovskite Materials and Applications
- Electronic and Structural Properties of Oxides
- Organic and Molecular Conductors Research
- Molecular Junctions and Nanostructures
- Iron oxide chemistry and applications
- Chalcogenide Semiconductor Thin Films
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced Memory and Neural Computing
University of Wyoming
2020-2025
Purdue University West Lafayette
2011-2021
National Institute of Standards and Technology
2018-2021
Wyoming Department of Education
2020
Physical Measurement Laboratory
2018
Chinese Academy of Sciences
2005-2015
Institute of Physics
2005-2012
Czech Academy of Sciences, Institute of Physics
2008
Sun Yat-sen University
2008
Silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with controlled silica shell thicknesses were prepared by a modified Stöber method using 20 nm hydrophilic Fe3O4 NPs as seeds. The characterized X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area (SAED), and UV-Vis adsorption spectra (UV-Vis). results imply that consist of crystalline core an amorphous shell. thickness can be from 12.5 to 45 varying the experimental...
We report a study of graphene and field effect devices after exposure to series short pulses oxygen plasma. present data from Raman spectroscopy, back-gated field-effect magneto-transport measurements. The intensity ratio between "D" "G" peaks, I(D)/I(G) (commonly used characterize disorder in graphene) is observed increase approximately linearly with the number (N(e)) plasma etching initially, but then decreases at higher Ne. also discuss implications our for extracting crystalline domain...
Large-scale hydrophilic Fe 3O 4 nanoparticles (NPs) were prepared in the presence of citrate and sodium nitrate via a facile method. The NPs are quite stable can be freely dispersed water. as-prepared magnetic nanoparticle solution for more than 1 month. mean diameter controlled range ∼20 to ∼40 nm diameter. show superparamagnetic properties with relatively high saturation magnetization moment 58 emu/mg at room temperature. Furthermore, possible formation mechanism is proposed explain why...
Monodisperse Au, Ag, and Au3Pd nanoparticles (NPs) with narrow size distribution are prepared by direct reaction of the related metal salt oleylamine in toluene. Oleylamine serves as both a reducing agent surfactant synthesis. The sizes shape these NPs tuned temperatures. hydrophobic oleylamine-coated can be made water soluble replacing 3-mercaptopropionic acid. Both surface plasmonic resonance (SPR) enhanced Raman scattering (SERS) observed from Au Ag found to NP size- surface-dependent.
Electron beam exposure is a commonly used tool for fabricating and imaging graphene-based devices. Here we present study of the effects electron-beam irradiation on electronic transport properties graphene operation field-effect transistors (GFET). Exposure to 30 keV caused negative shifts in charge-neutral point (CNP) GFET, interpreted as due n-doping from interaction energetic electron with substrate. The shift CNP substantially reduced suspended seen also decrease carrier mobilities...
Bi2Se3 is an important semiconductor thermoelectric material and a prototype topological insulator. Here we report observation of Shubnikov-de Hass oscillations accompanied by quantized Hall resistances (R(xy)) in highly doped n-type with bulk carrier concentrations few 10(19) cm(-3). Measurements under tilted magnetic fields show that the magnetotransport 2D-like, where only c-axis component field controls Landau level formation. The step size 1/R(xy) found to scale sample thickness,...
We report on electronic properties of graphene synthesized by chemical vapor deposition (CVD) copper then transferred to SiO2/Si. Wafer-scale (up 4 in.) films have been synthesized, consisting dominantly monolayer as indicated spectroscopic Raman mapping. Low temperature transport measurements are performed microdevices fabricated from such CVD graphene, displaying ambipolar field effect (with on/off ratio ∼5 and carrier mobilities up ∼3000 cm2/V s) “half-integer” quantum Hall effect, a...
We have investigated the effects of thermal annealing on ex-situ chemically vapor deposited submonolayer graphene islands polycrystalline Cu foil at atomic-scale using ultrahigh vacuum scanning tunneling microscopy. Low-temperature annealed (at ∼430 °C) exhibit predominantly striped Moiré patterns, indicating a relatively weak interaction between and underlying foil. Rapid high-temperature sample 700–800 gives rise to removal oxide recovery crystallographic features copper that surrounds...
Topological insulators (TIs) are an unusual phase of quantum matter with nontrivial spin-momentum locked topological surface states (TSS). The electrical detection locking the TSS in 3D TIs has been lacking till very recently. Many results measured on samples significant bulk conduction, such as metallic Bi2Se3, where it can be challenging to separate and contribution spin signal. Here, we report potentiometric measurements thin flakes exfoliated from insulating TI Bi2Te2Se (BTS221)...
We report a current-induced, persistent, long-lived, and rewritable electron spin polarization in 3D topological insulator.
We report an atomically resolved scanning tunneling microscopy investigation of the edges graphene grains synthesized on Cu foils by chemical vapor deposition. Most are macroscopically parallel to zigzag directions lattice. These have microscopic roughness that is found also follow at atomic scale, displaying many ∼120° turns. A prominent standing wave pattern with periodicity ∼3a/4 (a being lattice constant) observed near a rare-occurring armchair-oriented edge. Observed features this...
An atomic-scale study utilizing scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV) is performed on large single crystalline graphene grains synthesized Cu foil by a chemical vapor deposition (CVD) method. After thermal annealing, we observe the presence of periodic surface depressions (stripe patterns) that exhibit long-range order formed area covered graphene. We suggest observed stripe pattern reconstruction partial dislocations (which appeared to be stair-rod-like) resulting...
Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most commonly observed (MR) phenomena in topological insulators (TIs) often attributed to the Dirac surface states (TSS). However, ambiguities exist because these could also come from bulk (often carrying significant conduction many TIs) observable even non-TI materials. Here, we demonstrate back-gated ambipolar TI field-effect transistors (Bi0.04Sb0.96)2Te3 thin films grown by molecular beam epitaxy on SrTiO3(111),...
Aligned single crystalline boron nanowire arrays are formed by thermal carbon reduction. The SEM image shows an array of nanowires (ca. 5 µm long) vertically aligned in high density on a Si substrate. These have enhancement factor, good emission stability, and can endure current, which suggest they excellent candidate for field-emission applications.
Single crystalline boron nanocones are obtained by a simple chemical vapor deposition method. Electric conductivity values of (1.0–7.3) × 10–5 (Ω cm)–1. Results field emission show the low turn-on and threshold electric fields about 3.5 V μm–1 5.3 μm–1, respectively. Boron with good electrical transport properties promising candidates for application in flat panel displays nanoelectronics building blocks.
We have performed scanning gate microscopy (SGM) on graphene field effect transistors (GFET) using a biased metallic nanowire coated with dielectric layer as contact mode tip and local top gate. Electrical transport through at various back voltages is monitored function of voltage position. Near the Dirac point, response resistance to shows significant variation position, SGM imaging displays mesoscopic domains electron-doped hole-doped regions. Our measurements reveal substantial spatial...
Abstract Recent experiments show that topological surface states (TSS) in insulators (TI) can be exploited to manipulate magnetic ordering ferromagnets. In principle, TSS should also exist for other materials, but it remains unexplored as whether such utilized Herein, current‐induced magnetization switching enabled by a non‐TI material, namely, Dirac semimetal α‐Sn, is reported. The use an α‐Sn/Ag/CoFeB trilayer structure. the CoFeB layer switched charge current at room temperature, without...
Pyramid-like Fe3O4 nanostructures (see Figure) are formed over large areas on α-Fe2O3(0001) substrates using a plasma-sputtering technique. No catalysts or templates used in the reaction process. This nanostructure resembles Egyptian pyramids, possessing many layers and standing perpendicular to substrate surface. These structures may have potential applications constructing nanoscale magnetic high-density storage devices.
Transition metal dichalcogenides (TMDs) are attractive materials for a variety of applications in solar energy conversion and electrocatalysis, due to their favorable optical electrical properties unique two-dimensional structures which facilitate the fabrication wide-area, ultrathin layers. Unfortunately, basal planes make up majority these relatively inert, thus great deal effort has been directed engineering favorable, catalytically active defects into materials. Here, we demonstrate how...