A5040273198- Physics of Superconductivity and Magnetism
- Organic and Molecular Conductors Research
- Semiconductor materials and devices
- Fullerene Chemistry and Applications
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Graphene research and applications
- Magnetic and transport properties of perovskites and related materials
- Integrated Circuits and Semiconductor Failure Analysis
- Silicon and Solar Cell Technologies
- Solid-state spectroscopy and crystallography
- Boron and Carbon Nanomaterials Research
- Electronic and Structural Properties of Oxides
- Advancements in Semiconductor Devices and Circuit Design
- Magnetic properties of thin films
- Copper Interconnects and Reliability
- Ferroelectric and Piezoelectric Materials
- Inorganic Chemistry and Materials
- Advanced Chemical Physics Studies
- Rare-earth and actinide compounds
- Molecular Junctions and Nanostructures
- Superconductivity in MgB2 and Alloys
- High-pressure geophysics and materials
- High voltage insulation and dielectric phenomena
- Acoustic Wave Resonator Technologies
Manitoba Hydro
2018-2019
Curtiss-Wright (United Kingdom)
2018-2019
University of Potsdam
2018-2019
University of Strathclyde
2018-2019
University of Southampton
2018-2019
TissuPath
2010-2018
Sandia National Laboratories California
2006-2016
Sandia National Laboratories
2006-2016
Philadelphia University
2014
University of Guelph
1991-2013
Single crystal sof the 84-K superconductor ${\mathrm{Bi}}_{2.2}{\mathrm{Sr}}_{2}{\mathrm{Ca}}_{0.8}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ were characterized by x-ray diffraction, dc magnetic susceptibility, electrical resistivity, and microwave absorption. The structure has ${[\mathrm{Cu}{\mathrm{O}}_{2}]}_{\ensuremath{\infty}}$ planes separated calcium atoms, edge-shared bismuth oxide double layers, an incommensurate superlattice along $b$ with a period of 4.76. in-plane...
The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable revert to pristine on reheating 300 degrees C at ambient pressure. For synthesis temperatures between 400 pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with lattice parameter a(o) = 13.6 angstroms. When treated 500 800 the same pressure, transforms rhombohedral hexagonal parameters 9.22 angstroms c(o) 24.6 intermolecular distance small...
Single-crystal epitaxial thin films of the isotropic metallic oxides Sr1-xCaxRuO(3) (0 </= x 1) were grown on miscut SrTiO(3)(100) substrates in situ by 90 degrees off-axis sputtering. These exhibit low resistivities, excellent chemical and thermal stability, good surface smoothness, high crystalline quality. Furthermore, lattice parameters magnetic properties can be varied simply changing strontium/calcium ratio. films, their multilayer structures with other oxide materials, used for...
N-channel field effect transistors with excellent device characteristics have been fabricated by utilizing C60 as the active element. Measurements on thin films in ultrahigh vacuum show on-off ratios high 106 and mobilities up to 0.08 cm2/V s.
We characterize the molecular reorientational dynamics in two phases of solid ${\mathrm{C}}_{60}$ with $^{13}\mathrm{C}$ NMR measurements. A change nature dynamics, indicated by a kinetic parameters extracted from spin-lattice relaxation data, occurs at phase transition 260 K. Above transition, molecules appear to execute continuous rotational diffusion; below they jump between symmetry-equivalent orientations. This interpretation is consistent x-ray-diffraction results Heiney et al. as well...
Previous high-resolution electron microscopy (HREM) observations of the carbon nanotubes have led to a "Russian doll" structural model that is based on hollow concentric cylinders capped at both ends. The structures and particles were characterized here by bulk physical chemical property measurements. individual nanostructure as compressible graphite in c axis, such nanostructures can be intercalated with potassium rubidium, leading saturation composition "MC(8)." These results are counter...
Two new effects associated with Fr\"ohlich sliding-mode conductivity have been observed in Nb${\mathrm{Se}}_{3}$. First, nonlinear resistance is only after a well-defined threshold field reached. Second, electric fields above the result noise potential difference across current biased specimen. We interpret as direct evidence of charge-density wave depinning and motion.
Colossal magnetoresistance with more than a thousandfold change in resistivity (ΔR/RH=127 000% at 77 K, H=6 T) has been obtained epitaxially grown La-Ca-Mn-O thin films. This value is about three orders of magnitude higher typically seen the giant-magnetoresistance-type metallic, superlattice The temperature peak located region metallic behavior. As occurs not magnetic transition but where magnetization still substantial, spin-disorder scattering likely to be main mechanism these highly...
Epitaxial ferroelectric SrRuO3/Pb(Zr0.52Ti0.48)O3/SrRuO3 heterostructures have been fabricated employing isotropic metallic oxide electrodes on (100) SrTiO3 and Si with an yttria stabilized zirconia buffer layer. The structures grown in situ by 90° off-axis sputtering, which allows the growth of uniform stoichiometric films over large areas excellent step coverage. X-ray diffraction, Rutherford backscattering spectroscopy, cross-sectional transmission electron microscopy reveal high...
A strongly anisotropic resistivity tensor was measured from ${T}_{c}=81 \mathrm{to} 600$ K in crystals of the new high-${T}_{c}$ superconductor ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2.2}$${\mathrm{Ca}}_{0.8}$ ${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8}$. The $a\ensuremath{-}b$ plane anisotropy is $\frac{{\ensuremath{\rho}}_{a}}{{\ensuremath{\rho}}_{b}}\ensuremath{\approx}2$, with ${\ensuremath{\rho}}_{a}$ and ${\ensuremath{\rho}}_{b}$ linear $T$. perpendicular component...
A detailed study has been made of interdiffusion in (GaAs)n(AlAs)m multilayer structures grown by molecular beam epitaxy. The subscripts n and m indicate that the structure is a repeating sequence monolayers GaAs followed AlAs. time dependence Fourier components composition modulation at constant annealing temperature was obtained measuring intensities superlattice satellites x-ray diffraction. For sample with (n,m) = (12,9) 860 °C, data can be fit composition-dependent diffusion coefficient...
Thermal sublimation of pure C60 and C70 has been used for depositing well-characterized fullerene films on a variety substrates. Film purity is determined by infrared absorption spectra the extent crystallinity face-centered cubic structure x rays. Thickness-dependent optical electrical measurements reveal uniform over thickness range 200–1000 Å. We obtain coefficients having values between those Si Ge relative permittivity value close to that amorphous SiO2.
Bulk-sensitive, polarization-dependent oxygen K- and copper L-edge absorption spectra of single-domain ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ with ${\mathrm{CuO}}_{2}$ planes tilted off the sample surface were measured. A novel experimental configuration was utilized to achieve complete polarization geometry eliminate optical path variations. Contrary previous measurements, our data show for both intrinsic doped holes a...
The dissipation observed at the superconducting transition of high-${T}_{c}$ superconductor ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$Ca${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8}$ is explained quantitatively by Kosterlitz-Thouless theory vortex-antivortex pair excitations within Cu${\mathrm{O}}_{2}$ planes. This conclusion drawn from observation an exponential square-root singularity in resistivity and a power-law dependence on magnetic field. phase (${T}_{c}=84.7$ K) $\ensuremath{\rho}=0$ point,...
X-ray scattering studies of Nb${\mathrm{Se}}_{3}$ show the formation two independent, incommensurate charge-density waves (CDW) with wave vectors ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}}_{1}=(0, 0.243, 0)$ and ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}}_{2}=(0.5, 0.263, 0.5)$ at ${T}_{1}=144$ K ${T}_{2}=59$ K, respectively. Electric fields that suppress resistive anomaly associated lower-temperature CDW have no measurable effect on either amplitude or vector. The field...
Transport anisotropies of ${\ensuremath{\rho}}_{c}$.${\ensuremath{\rho}}_{\mathrm{ab}}$\ensuremath{\simeq}${10}^{4}$ to ${10}^{5}$ were measured for superconducting and nonsuperconducting ${\mathrm{Bi}}_{2+\mathrm{x}}$${\mathrm{Sr}}_{2\mathrm{\ensuremath{-}}\mathrm{y}}$${\mathrm{CuO}}_{6\ifmmode\pm\else\textpm\fi{}\mathrm{\ensuremath{\delta}}}$ crystals. In samples ${\ensuremath{\rho}}_{\mathrm{ab}}$ increases linearly with temperature from just above ${T}_{c}$\ensuremath{\simeq}7 700 K. The...