A5014610741- Electronic and Structural Properties of Oxides
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor materials and devices
- ZnO doping and properties
- Magnetic and transport properties of perovskites and related materials
- Ferroelectric and Piezoelectric Materials
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Catalytic Processes in Materials Science
- Advanced Materials Characterization Techniques
- Quantum Dots Synthesis And Properties
- Semiconductor materials and interfaces
- Copper-based nanomaterials and applications
- 2D Materials and Applications
- Surface and Thin Film Phenomena
- Graphene research and applications
- Ion-surface interactions and analysis
- Silicon and Solar Cell Technologies
- Magnetic properties of thin films
- Gas Sensing Nanomaterials and Sensors
- Microstructure and mechanical properties
- Integrated Circuits and Semiconductor Failure Analysis
- Plasmonic and Surface Plasmon Research
- Iron-based superconductors research
Oak Ridge National Laboratory
2015-2024
University of Tennessee at Knoxville
2014-2024
Government of the United States of America
2020-2023
Rutgers, The State University of New Jersey
2021
Vanderbilt University
2020
Sungkyunkwan University
2020
Institute for Basic Science
2020
Ulsan National Institute of Science and Technology
2020
Pohang University of Science and Technology
2020
Center for Nanophase Materials Sciences
2020
The long-standing problem of growing a commensurate crystalline oxide interface with silicon has been solved. Alkaline earth and perovskite oxides can be grown in perfect registry on the (001) face silicon, totally avoiding amorphous silica phase that ordinarily forms when is exposed to an oxygen containing environment. physics heteroepitaxy lies establishing sequenced transition uniquely addresses thermodynamics layer-by-layer energy minimization at interface. A metal-oxide-semiconductor...
Most studied two-dimensional (2D) materials exhibit isotropic behavior due to high lattice symmetry; however, lower-symmetry 2D such as phosphorene and other elemental very interesting anisotropic properties. In this work, we report the atomic structure, electronic properties, vibrational modes of few-layered PdSe2 exfoliated from bulk crystals, a pentagonal layered noble transition metal dichalcogenide with puckered morphology that is air-stable. Micro-absorption optical spectroscopy...
Single-atom catalysts (SACs) are the smallest entities for catalytic reactions with projected high atomic efficiency, superior activity, and selectivity; however, practical applications of SACs suffer from a very low metal loading 1-2 wt%. Here, class based on atomically dispersed transition metals nitrogen-doped carbon nanotubes (MSA-N-CNTs, where M = Ni, Co, NiCo, CoFe, NiPt) is synthesized an extraordinarily loading, e.g., 20 wt% in case NiSA-N-CNTs, using new multistep pyrolysis process....
Despite the use of electrons with wavelengths just a few picometers, spatial resolution in transmission electron microscope (TEM) has been limited by spherical aberration to typically around 0.15 nanometer. Individual atomic columns crystalline lattice can therefore only be imaged for low-order orientations, limiting range defects that at resolution. The recent development correctors microscopy allows this limit overcome. We present direct images from an aberration-corrected scanning TEM...
Solar photocatalysis is a potential solution to satisfying energy demand and its resulting environmental impact. However, the low electron-hole separation efficiency in semiconductors has slowed development of this technology. The effect defects on not always clear. A model atomically thin structure single-unit-cell Bi3 O4 Br nanosheets with surface proposed boost photocatalytic by simultaneously promoting bulk- surface-charge separation. Defect-rich displays 4.9 30.9 times enhanced hydrogen...
Abstract Ordered mesoporous carbons (OMCs) have demonstrated great potential in catalysis, and as supercapacitors adsorbents. Since the introduction of organic–organic self-assembly approach 2004/2005 until now, direct synthesis OMCs is still limited to wet processing phenol-formaldehyde polycondensation, which involves soluble toxic precursors, acid or alkali catalysts, requires multiple steps, thus restricting widespread application OMCs. Herein, we report a simple, general, scalable...
The development of stable and efficient hydrogen evolution reaction (HER) catalysts is essential for the production as a clean energy resource. A combination experiment theory demonstrates that normally inert basal planes 2D layers MoS2 can be made highly catalytically active HER when alloyed with rhenium (Re). presence Re at ≈50% level converts material to distorted tetragonal (DT) structure shows enhanced activity compared most -based reported in literature. More importantly, this new...
Atomically thin two-dimensional (2D) materials face significant energy barriers for synthesis and processing into functional metastable phases such as Janus structures. Here, the controllable implantation of hyperthermal species from pulsed laser deposition (PLD) plasmas is introduced a top-down method to compositionally engineer 2D monolayers. The kinetic energies Se clusters impinging on suspended monolayer WS2 crystals were controlled in <10 eV/atom range with situ plasma diagnostics...
The remarkable properties of black TiO2 are due to its disordered surface shell surrounding a crystalline core. However, the chemical composition and atomic electronic structure relationship core remain poorly understood. Using advanced transmission electron microscopy methods, we show that outermost layer nanoparticles consists Ti2O3 shell. measurements transition region connects perfect rutile consisting first four five monolayers defective rutile, containing clearly visible Ti...
The first examples of single crystal epitaxial thin films a high entropy perovskite oxide are synthesized. Pulsed laser deposition is used to grow the configurationally disordered ABO3 perovskite, Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3, epitaxially on SrTiO3 and MgO substrates. X-ray diffraction scanning transmission electron microscopy demonstrate that phase with excellent crystallinity atomically abrupt interfaces underlying Atomically-resolved energy loss spectroscopy mapping shows uniform...
The critical impact of epitaxial stress on the stabilization ferroelectric orthorhombic phase hafnia is proved. Epitaxial bilayers Hf0.5Zr0.5O2 (HZO) and La0.67Sr0.33MnO3 (LSMO) electrodes were grown a set single crystalline oxide (001)-oriented (cubic or pseudocubic setting) substrates with lattice parameter in 3.71–4.21 Å range. strain LSMO electrode, determined by mismatch substrate, HZO. On tensilely strained electrodes, most HZO film orthorhombic, whereas monoclinic favored when relaxed...
The magnetic and structural properties of cobalt-implanted ZnO single crystals are reported. High-quality, (110)-oriented single-crystal Sn-doped substrates were implanted at ∼350 °C with Co to yield transition metal concentrations 3–5 at. % in the near-surface (∼2000 Å) region. After implantation, samples subject a 5 min rapid thermal annealing 700 °C. Magnetization measurements indicate ferromagnetic behavior, hysteresis observed M vs H behavior T=5 K. Coercive fields ⩽100 Oe this...
▪ Abstract In the nanoscience era, properties of many exciting new materials and devices will depend on details their composition down to level single atoms. Thus characterization structure electronic matter at atomic scale is becoming ever more vital for economic technological as well scientific reasons. The combination atomic-resolution Z-contrast scanning transmission electron microscopy (STEM) energy loss spectroscopy (EELS) represents a powerful method link macroscopic properties,...
Deformation of metals and alloys by dislocations gliding between well-separated slip planes is a well-understood process, but most crystal structures do not possess such simple geometric arrangements. Examples are the Laves phases, common class intermetallic compounds exist with ordered cubic, hexagonal, rhombohedral structures. These usually brittle at low temperatures, transformation from one structure to another slow. On basis energetic considerations, dislocation-based mechanism...
In vapor-liquid-solid (VLS) growth, the liquid phase plays a pivotal role in mediating mass transport from vapor source to growth front of nanowire. Such often takes place through phase. However, we observed by situ transmission electron microscopy different behavior for self-catalytic VLS sapphire nanowires. The occurs layer-by-layer fashion and is accomplished interfacial diffusion oxygen ordered aluminum atoms. Oscillatory dissolution reactions at top rim nanowires occur supply required...