A5049000751- Photonic and Optical Devices
- Photonic Crystal and Fiber Optics
- Advanced Fiber Optic Sensors
- Optical Network Technologies
- High-pressure geophysics and materials
- Advanced Fiber Laser Technologies
- Photonic Crystals and Applications
- Diamond and Carbon-based Materials Research
- Boron and Carbon Nanomaterials Research
- Advanced Thermoelectric Materials and Devices
- Carbon Nanotubes in Composites
- Thin-Film Transistor Technologies
- Semiconductor Lasers and Optical Devices
- Silicon Nanostructures and Photoluminescence
- Graphene research and applications
- X-ray Diffraction in Crystallography
- Fullerene Chemistry and Applications
- Rare-earth and actinide compounds
- Physics of Superconductivity and Magnetism
- Thermal properties of materials
- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Metal and Thin Film Mechanics
- Crystallization and Solubility Studies
- Chalcogenide Semiconductor Thin Films
Pennsylvania State University
2014-2023
University of Southampton
2006-2020
Wright-Patterson Air Force Base
2020
University of Illinois Chicago
2020
George Washington University
2020
Geophysical Laboratory
1990-2011
Carnegie Institution for Science
1991-2011
Cornell University
1999-2006
National Institute of Allergy and Infectious Diseases
2006
National Institutes of Health
2006
We present a method of modeling transport coefficients from first-principles calculations. introduce the distribution that contains all electronic information and which can easily be calculated. use this to analyze ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ calculate its for comparison with experiment. The gives an improved insight into relationship between properties structure is valuable tool in search thermoelectric materials.
Deposition of semiconductors and metals from chemical precursors onto planar substrates is a well-developed science technology for microelectronics. Optical fibers are an established platform both communications fundamental research in photonics. Here, we describe hybrid that integrates key aspects engineering disciplines, demonstrating the fabrication tubes, solid nanowires, coaxial heterojunctions, longitudinally patterned structures composed metals, single-crystal semiconductors,...
Infrared (IR) fibers offer a versatile approach to guiding and manipulating light in the IR spectrum, which is becoming increasingly more prominent variety of scientific disciplines technological applications. Despite well-established efforts on fabrication past decades, number remarkable breakthroughs have recently rejuvenated field—just as related areas optical technology are reaching maturation. In this review, we describe both history recent developments design fibers, including glass...
Optical observations and x-ray diffraction measurements of the reaction between iron hydrogen at high pressure to form hydride are described. The is associated with a sudden pressure-induced expansion 3.5 gigapascals samples immersed in fluid hydrogen. Synchrotron carried out 62 demonstrate that has double hexagonal close-packed structure, cell volume up 17% larger than pure iron, stoichiometry close FeH. These results greatly extend range over which technologically important iron-hydrogen...
There is widespread interest in the search for materials that would allow fabrication of more efficient thermoelectric devices cooling and power generation applications. Here, we report a large increase p-doped antimony bismuth telluride alloys upon pressure tuning under nonhydrostatic compression conditions. Together with measurements electrical conductivity an upper bound estimated thermal pressure, these results indicate values dimensionless figure merit, ZT, excess 2 have been achieved,...
Size-tuned thiol-capped bismuth telluride nanoparticles (see image) are synthesized and annealed to make phase-pure nanostructured material. These materials exhibit relatively high thermoelectric power unusually low temperature-independent thermal conductivity, the latter due phonon scattering. Detailed facts of importance specialist readers published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted by authors. Please...
High purity crystalline ZnSe compound semiconductor waveguides are fabricated inside optical fibers via high-pressure chemical vapor deposition. These fiber exhibit very low loss (e.g., <1 dB cm−1 at 1550 nm wavelength). The superior and electronic properties of semiconductors can now be exploited in a geometry. Detailed facts importance to specialist readers published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted by...
Synthesis of well-ordered reduced dimensional carbon solids with extended bonding remains a challenge. For example, few single-crystal organic monomers react under topochemical control to produce solids. We report mechanochemical synthesis in which slow compression at room temperature uniaxial stress can convert polycrystalline or benzene monomer into single-crystalline packings nanothreads, one-dimensional sp3 nanomaterial. The long-range order over hundreds microns these crystals allows...
Carbon nanothreads are a new one-dimensional sp3 carbon nanomaterial. They assemble into hexagonal crystals in room temperature, nontopochemical solid-state reaction induced by slow compression of benzene to 23 GPa. Here we show that pyridine also reacts under form well-ordered product: C5NH5 nitride nanothreads. Solid has different crystal structure from solid benzene, so the formation low-dimensional crystalline solids small aromatics may be general phenomenon enables chemical design...
How might fully saturated benzene polymers of composition [(CH)6]n form under high pressure? In the first approach to answering this question, we examine stepwise increase in saturation a one-dimensional stack molecules by enumerating partially polymer intermediates, subject constraints unit cell size and energy. Defining number four-coordinate carbon atoms per formula as degree saturation, set isomers for degree-two degree-four can be generated either thinking propagation building blocks or...
▪ Abstract The synthesis, characterization, and tuning of solid state materials by means high-pressure techniques is reviewed from the perspective a chemist. Because pressure can affect significant changes in reaction equilibria, it useful tool for synthesis novel metastable materials. Several different examples ranging behavior carbon under to oxide intermetallic compounds are presented illustrate breadth opportunities this area. Pressure allows precise fundamental parameter, interatomic...
We present first-principles transport calculations for ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ using the linearized-augmented plane-wave method and relaxation time approximation. considered effects of hydrostatic pressure uniaxial stress up to 4 GPa. Doping was included electrons holes at levels ${10}^{21}/{\mathrm{cm}}^{3}.$ The electrical conductivity, Seebeck coefficient, power factor are derived from calculated distribution. Our results electronic structure properties in qualitative...
The synthesis of poly(phenylcarbyne), one a class carbon-based random network polymers, is reported. backbone this polymer composed tetrahedrally hybridized carbon atoms, each bearing phenyl substituent and linking, by means three carbon-carbon single bonds, into three-dimensional fused rings. This atomic-level confers unusual properties on the polymer, including facile thermal decomposition, which yields diamond or diamond-like phases at atmospheric pressure.
Flexible Si p-i-n junction fibers made by high pressure chemical vapor deposition offer new opportunities in textile photovoltaics and optoelectronics, as exemplified their photovoltaic properties, gigahertz bandwidth for photodetection, ability to waveguide light. As a service our authors readers, this journal provides supporting information supplied the authors. Such materials are peer reviewed may be re-organized online delivery, but not copy-edited or typeset. Technical support issues...
Carbon nanothreads are a new type of one-dimensional sp3-carbon nanomaterial formed by slow compression and decompression benzene. We report characterization the chemical structure 13C-enriched advanced quantitative, selective, two-dimensional solid-state nuclear magnetic resonance (NMR) experiments complemented infrared (IR) spectroscopy. The width NMR spectral peaks suggests that nanothread reaction products much more organized than amorphous carbon. In addition, there is no evidence from...
Carbon nanothreads, which are one-dimensional sp3-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids constructed through pressure-induced polymerization of sp2 molecules such as benzene. Whereas a few examples nanothreads have been reported, the need for onset pressures (≥17 GPa) synthesize them precludes scalability limits scope. Herein, we report scalable synthesis based on molecular furan, can be...
The sp3-bonded "transparent phase" of carbon, formed by compression single-crystal graphite to 18 GPa, has been found be quenchable atmospheric pressure at low temperatures (<100 K). quenched transparent phase reverts upon warming room temperature, indicating that there is a surprisingly small activation barrier for transformation must involve carbon−carbon bond breakage. Visual observations and Raman spectroscopy are used document the novel ambient transformation.
At high pressure the alkali metals potassium, rubidium, and cesium transform to that have a d1 electron configuration, becoming transition metal-like. As result, compounds were shown form between potassium metal nickel. These results demonstrate chemical behavior of under is very different from ambient conditions, where do not react because large differences in size electronic structure. They also significant implications for hypothesis incorporated into Earth's core.
Germanium sulphide glass thin films have been deposited on CaF2 and Schott N-PSK58 substrates directly by means of chemical vapor deposition (CVD). The rate germanium film this CVD process is estimated about 12 microm/hr at 500oC. These characterized micro-Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). Their transmission range extends from 0.5microm to 7microm measured UV-VIS-NIR FT-IR spectroscopy. refractive index prism coupling technique was 2.093+/-0.008...
Silicon fibers are fabricated using a high pressure chemical deposition technique to deposit the semiconductor material inside silica capillary. The silicon is deposited in an amorphous state into pure capillaries and can be crystallized polysilicon after via temperature anneal. Optical transmission measurements of various polycrystalline core materials were performed order determine their linear losses. Incorporating functionality fiber geometry opens up new possibilities for next...