A5019486456- Physics of Superconductivity and Magnetism
- Superconducting Materials and Applications
- Engineering Education and Curriculum Development
- Biomedical and Engineering Education
- Superconductivity in MgB2 and Alloys
- Nanowire Synthesis and Applications
- Quantum and electron transport phenomena
- Problem and Project Based Learning
- Polyoxometalates: Synthesis and Applications
- Solid-state spectroscopy and crystallography
- Magnetic properties of thin films
- Photonic and Optical Devices
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties and Applications
- Superconducting and THz Device Technology
- Spectroscopy and Quantum Chemical Studies
- Interdisciplinary Research and Collaboration
- Complex Systems and Decision Making
- Engineering Education and Pedagogy
- Photonic Crystals and Applications
- Copper Interconnects and Reliability
- Advanced Electrical Measurement Techniques
- Design Education and Practice
- Magnetic confinement fusion research
- Magnetic Properties of Alloys
Harvard University
1984-2023
Los Angeles Pierce College
2020
American Society For Engineering Education
2020
School of Sea
2020
Harvard University Press
1980-2020
Cornell University
2020
Polaroid (United States)
1984-2002
University of Colorado Boulder
1978-1982
University of Cincinnati
1977-1979
American University of Beirut
1973-1975
Nanowires have promising applications as photodetectors with superior ability to tune absorption morphology. Despite their high optical absorption, the quantum efficiencies of these nanowire remain low due difficulties in fabricating a shallow junction using traditional doping methods. As an alternative, we report nonconventional radial heterojunction photodiodes obtained by conformal coating indium oxide layer on silicon arrays. The has work function which induces strong inversion and...
Specific-heat measurements are reported for BaMn${\mathrm{F}}_{4}$ in the temperature region around its incommensurate phase transition. At ${T}_{I}=255.3$ K a mean-field discontinuity of 0.4 cal/mol is observed upon which superimposed power-law divergence 6.4 \ifmmode\pm\else\textpm\fi{} 0.5 cal/mol. The shape and magnitude compared with theoretical predictions Levanyuk, Osipov, Sigov, Sobyanin; good agreement observed. A second, smaller ${C}_{P}$ anomaly at 247.1 integrated 0.3 0.1 This...
Population aging is a defining demographic reality of our era. It associated with an increase in the societal burden delivering care to older adults chronic conditions or frailty. How integrate global population and technology development help address growing demands for facing many societies both challenge opportunity innovation. We propose social approach that promotes use technologies assist individuals, families, communities cope more effectively disabilities who can no longer live...
All-dielectric nanoarrays have strong electromagnetic resonances with various interesting applications and are tuned by adjusting their geometrical parameters. However, optical properties permanently encoded during fabrication. This study presents robust dynamically tunable all-dielectric nanoresonators for controllable, reversible, reproducible color filtering. Our design uses an array of TiO
We report investigations of the effect noise on Josephson in small-area tunnel junctions, both at dc and when junction is irradiated by 604-GHz laser radiation. The junctions were made Sn-SnO-Pb layers ~1 ${\mathrm{\ensuremath{\mu}}\mathrm{m}}^{2}$ area, fabricated crystal quartz substrates with integral planar resonant dipole antennas. observed systematic falloff ${I}_{c}{R}_{n}$ product increasing resistance can be accounted for thermal activation model (transition-state theory) if an...
We have measured the ac Josephson effect in small-area superconducting tunnel junctions at 604 GHz (λ=496 μm) using a resonant planar dipole antenna to couple radiation into junction. In 176-Ω junction, we observed up 7th step (at 8.75 mV), performance comparable that seen point contacts. also compare our data with results of RSJ model and Werthamer theory.
Recent developments on in situ formed multifilamentary composites are reviewed and their superconducting mechanical properties discussed terms of the underlying physical mechanisms. The evidence is presented for a strong size dependence strengthening, flux-pinning coupling mechanisms and, turn, composite normal-state transport properties. importance microstructure micro-geometry illustrated with data Cu-Nb, Cu-Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Raman spectra of single crystals silver iodide tetratungstate (Ag26I18W4O16) have been obtained as a function temperature from 77 to 350 K. These data indicate the presence structural phase transitions near 199 and 285 Dielectric conductivity measurements perpendicular unique twofold axis confirm these two transition temperatures. Plots log (σT) versus 1/T reveal three distinct regions linearity with activation energy 2.4 eV below K; 0.07 between 0.42 above
An analysis of the dielectric measurements for ferroelectric phase transition in superionic conductor Ag26I18W4O16 is reported. The interpreted as being slightly first order, with a hysteresis region less than 2.5 °K width. system obeys Curie–Weiss dependences both phases, constant satisfying equation paraelectric and phase. order–disorder-type involves mobile silver ions. frequency dependence ionic conductivity has been measured high temperature From 0.5 to 10.0 kHz it satisfies σ (ω)...
Cu-V3Ga composites were prepared from in situ formed multifilamentary Cu-V wires containing 20 vol.% of vanadium filaments. The highest value the upper critical field at 4.2 K reacted was found to be 22.4 T, with a corresponding midpoint superconducting transition 15.5 K. overall critical-current density compares favorably commercial V3Ga over entire range (2×105 A/cm2 4 104 18 T).
Critical current behavior and intrinsic superconducting properties of liquid quenched Nb3Al its pseudobinaries Nb3 (Al,Si) Nb3(Al,Ge) have been studied in fields up to 29 T. Our results show that flux pinning these materials is dominated by strong precipitate at low temperatures grain boundary high (&gt;10 K) temperatures. The best were obtained Nb75Al19Ge6 samples with Tc 20.0 K, estimated Hc2(0) 43 T Jc (4.2 excess 104 A/cm2 30
The effect of the uniaxial tensile stress on critical-current density Jc, and upper critical field Hc2, in situ formed Cu-V3Ga composites has been investigated. Jc was found to gradually decrease at stresses greater than ∼200 MPa. is small, amounting a only 20% 16 T 1 GPa. However, no permanent degradation observed even levels excess Similarly, Hc2 be rather insensitive applied stress. about 0.5 GPa fully recovered after releasing
Critical-current density, upper critical field, and hysteresis ac losses have been evaluated for a large (100-m long) sample of in situ formed Cu-Nb3Sn composite with superconducting volume fraction λ≃0.23. The magnetic field dependence the current, measured wire tape samples different reductions, cannot be explained by model based on single pinning mechanism. enhancement force highly reduced composites is attributed to surface flux at filament-matrix interfaces. Hysteretic obtained...
We have observed photon-assisted tunneling effects at 246 and 604 GHz in small-area superconductor-insulator-superconductor (SIS) superconductor-insulator-normal metal (SIN) superconducting junctions. find excellent agreement with the Tien–Gordon theory, infer that responsivity of SIN junctions approaches quantum limit low temperatures for photon energies less than 2Δ.
Changes in the heat capacity of solid electrolyte Ag26I18W4O16 are measured temperature range 150–330 K by differential scanning calorimetry. Our measurements, done on a powder sample, showed that has three phase transitions. At T1?199 and T2?248 K, this material exhibits first order transition with transformation H1=53±2 mcal/g H2=56±4 mcal/g. The at T3?277 is second characteristic lambda shape. T1 shows broad onset hysteresis (ΔT?4 K). Similarly, T2 hysteratic but ΔT?1 K. No associated...
We describe a cryostat for measuring the rf (100 kHz) susceptibility of insulators in temperature range from 300 to 4.2 K. The sample is connected by tube room and moved out coil tunnel diode oscillator located at constant low temperature. change frequency measured with digital counter. stable ±2 Hz over periods several hours. counter resolution attainable filling factor limit χ/Δχ about 2×104. anhydrous NiCl2 powder was evaluate apparatus determine
The field dependence of Raman scattering from $1S\ensuremath{\rightarrow}2S$, $1S\ensuremath{\rightarrow}3S$, and $1S\ensuremath{\rightarrow}2P$ transitions arsenic lithium acceptors in zinc telluride has been measured at magnetic fields up to 14 T. Eight electronic two impurity vibrational are identified ZnTe: As. Seven the originate $1{S}_{\frac{3}{2}}$ ground state. eighth originates photoexcited level $2{P}_{\frac{5}{2}}({\ensuremath{\Gamma}}_{7}^{\ensuremath{-}})$ terminates on vibronic...
Recent Möessbauer studies of magnetic films have described the orientational distribution spins in terms a mean angle orientation between spin direction and γ-ray propagation. These improperly interpreted quantity 〈sin2 θ〉, failed to account for effects saturation. We present an improved analysis which describes expansion spherical harmonics. Coefficients are determined from line intensities Zeeman-split spectra. A similar description, using same function, is applied angular dependence...