A5036206520- Advanced Thermoelectric Materials and Devices
- Chalcogenide Semiconductor Thin Films
- Magnetic and transport properties of perovskites and related materials
- Superconductivity in MgB2 and Alloys
- Phase-change materials and chalcogenides
- Thermal properties of materials
- Advanced Semiconductor Detectors and Materials
- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Semiconductor materials and devices
- Boron and Carbon Nanomaterials Research
- Electronic and Structural Properties of Oxides
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Advancements in Semiconductor Devices and Circuit Design
- Hydrogen Storage and Materials
- Advanced Thermodynamics and Statistical Mechanics
- Semiconductor materials and interfaces
- Multiferroics and related materials
- Thermodynamic and Structural Properties of Metals and Alloys
- Thermal Radiation and Cooling Technologies
- Ferroelectric and Piezoelectric Materials
- Magnetic properties of thin films
- nanoparticles nucleation surface interactions
- High-pressure geophysics and materials
Sandia National Laboratories
2012-2025
Sandia National Laboratories California
2009-2024
Rutgers, The State University of New Jersey
2001-2014
Office of Scientific and Technical Information
2009
San Jose State University
2009
National Technical Information Service
2009
We have investigated the detailed magnetic field dependence of electric polarization and dielectric constant in $(\mathrm{T}\mathrm{b},\mathrm{D}\mathrm{y},\mathrm{H}\mathrm{o}){\mathrm{M}\mathrm{n}}_{2}{\mathrm{O}}_{5}$ where ferroelectric transitions are intimately coupled. Our fundamental discovery is unprecedented large change with field, particularly ${\mathrm{D}\mathrm{y}\mathrm{M}\mathrm{n}}_{2}{\mathrm{O}}_{5}$, associated an unusual commensurate-incommensurate transition. This...
Two-dimensional (2D) metal-boride-derived nanostructures have been a focus of intense research for the past decade, with an emphasis on new synthetic approaches, as well exploration possible applications in next-generation advanced materials and devices. Their unusual mechanical, electronic, optical, chemical properties, arising from low dimensionality, present paradigm to science metal borides that has traditionally focused their bulk properties. This Perspective discusses current state 2D...
The thermal conductivity of the magnetically frustrated, ferroelectric YMnO3 exhibits an isotropic suppression in cooperative paramagnetic state, followed by a sudden increase upon magnetic ordering. This unprecedented behavior without associated static structural distortion probably originates from strong dynamic coupling between acoustic phonons and low-energy spin fluctuations geometrically frustrated magnets. replacement Ho for Y at ferroelectrically active site results even larger...
A reentrant charge ordering transition occurs within the $\ensuremath{\mu}\mathrm{m}$-scale phase-separated manganite ${(\mathrm{La},\mathrm{Pr})}_{5∕8}{\mathrm{Ca}}_{3∕8}\mathrm{Mn}{\mathrm{O}}_{3}$. This low-temperature state, in which charge-ordered and ferromagnetic-metallic phases coexist, accompanies spin-glass-like magnetism. Furthermore, thermal conductivity measurements reveal an irreversibility characteristic of a freezing lattice degrees freedom, strongly suggesting presence...
Bismuth telluride nanoparticles (NPs) have been synthesized using a low-temperature wet-chemical approach from bismuth(III) oleate and tri-n-octylphosphine telluride. The size shape of the NPs can be controlled by adjusting temperature, reaction time, nature surfactants solvents. Aromatic hydrocarbons (toluene, xylenes) ethers (phenyl- benzyl-ether) favor formation stoichiometric Bi2Te3 platelike morphology, whereas presence oleylamine 1-dodecanethiol yields Bi-rich spherical NPs. XRD, IR,...
Metal boride nanostructures have shown significant promise for hydrogen storage applications. However, the synthesis of nanoscale metal particles is challenging because their high surface energy, strong inter- and intraplanar bonding, difficult-to-control termination. Here, it demonstrated that mechanochemical exfoliation magnesium diboride in zirconia produces 3-4 nm ultrathin MgB2 nanosheets (multilayers) yield. High-pressure hydrogenation these multilayers at 70 MPa 330 °C followed by...
Granular metals, consisting of nanoscale conducting and insulating regions, have been studied for more than 50 years fundamental applied research. metals exhibit non-linear conductivity vs frequency behavior, consistent with the universal power law response, recently suggested high-pass filter applications. Here, we report that cobalt–silicon nitride (Co–SiNx) granular optimized sputter conditions post-growth annealing an exceptional 109 increase in at 1 MHz compared to DC conductivity. The...
An increasing magnetic field perpendicular to an undoped semiconductor surface at low temperature is known strengthen the binding of localized electrons stationary ions, as wavefunction's tails evolve from exponential Gaussian. It also that application a high bias voltage depleted can liberate bound charge and induce large drop in electrical resistance. We connect these established results experimental transport measurements on off-state germanium Schottky-barrier metal–oxide–semiconductor...
In the past decade, basic physics, chemistry, and materials science research on topological quantum materials—and their potential use to implement reliable computers—has rapidly expanded become a major endeavor. A pivotal goal of this has been realize hosting Majorana quasiparticles, thereby making computing technological reality. While remains elusive, recent data-mining studies, performed using chemistry methodologies, have identified thousands materials—some, perhaps many, with for...
Our results from various transport experiments on Mg1-xB2 indicate a surprising effect associated with the presence of Mg deficiency in MgB2: phase separation between Mg-vacancy rich and poor phases. The is superconducting, but insulating nature probably originates Anderson (disorder-induced) localization itinerant carriers. Furthermore, electron diffraction measurements that within vacancy-rich regions these defects tend to order intriguing patterns. This electronic shows similar, also...
In some cases, nanoscale microstructures improve thermoelectric efficiency, but this phenomenon has rarely been studied systematically for precipitates in bulk materials. We quantified the influence of nanostructuring on figure merit (zT) by embedding Sb2Te3 inclusions, from nanometer to micron sizes, an Sb-rich AgSbTe2 matrix through solid-state precipitation. Nucleation/growth and coarsening regimes precipitate formation had a clear effect transport properties, which could be understood...
The end members, Bi and Bi${}_{2}$Te${}_{3}$, of the infinitely adaptive (Bi${}_{2}$)${}_{m}$(Bi${}_{2}$Te${}_{3}$)${}_{n}$ series compounds have not only been revealed to be topological insulators under appropriate conditions, but also shown superconductors pressure, suggesting potential for bulk superconductor-topological-insulator interfaces associated quantum computing applications. Herein, we report pressure-dependent evolution structure electrical transport nominal semimetal...
We demonstrate chemical doping of a topological insulator Bi2Se3 using ion implantation. Ion beam-induced structural damage was characterized grazing incidence X-ray diffraction and transmission electron microscopy. reversed simple thermal annealing step. Carrier-type conversion achieved implantation followed by an activation anneal in thin films. These two sets experiments establish the feasibility for modification Bi2Se3, prototypical insulator. can, principle, be used any The direct...
Abstract High-fidelity single-shot readout of spin qubits requires distinguishing states much faster than the T 1 time state. One approach to improving fidelity and bandwidth (BW) is cryogenic amplification, where signal from qubit amplified before noise sources are introduced room-temperature amplifiers can operate at lower gain higher BW. We compare performance two amplification circuits: a current-biased heterojunction bipolar transistor circuit (CB-HBT), an AC-coupled HBT (AC-HBT). Both...
Abstract Skyrmions and antiskyrmions are nanoscale swirling textures of magnetic moments formed by chiral interactions between atomic spins in noncentrosymmetric materials multilayer films with broken inversion symmetry. These quasiparticles interest for use as information carriers next-generation, low-energy spintronic applications. To develop skyrmion-based memory logic, we must understand skyrmion-defect two main goals—determining how skyrmions navigate intrinsic material defects...
A germanium p-channel Schottky barrier metal–oxide–semiconductor field-effect transistor (SB-MOSFET) with germanium–platinum contacts is demonstrated experimentally. The fabrication process has a low thermal budget of 450° C and requires neither intentional doping nor ion implantation. At temperature 4 K, the SB-MOSFET turns on at gate voltage −1.6 V shows peak mobility 500 cm2/V s carrier density 3 × 1012 cm–2. Under high drain–source bias voltages, device operates in an unconventional mode...
The simple binary compound, MgB2, has created enormous excitement, due to its remarkably high Tc (39 K), exotic electronic and phononic structure, as well potential technological application. However, contrary the initial expectation, worldwide efforts enhance of this material by means chemical doping applying hydrostatic pressure have failed. Investigations other diborides or related materials also resulted in finding lower Tc’s. In letter we report a slight, but significant enhancement...
Thin film Bi2Te3/Sb2Te3 multilayers are thought to possess a high thermoelectric figure of merit. Our work describes how can be fabricated using electrodeposition, an inexpensive and scalable synthesis route. We address the challenge simultaneously maintaining satisfactory stoichiometry, crystallinity, scalability for this complex structure. have synthesized Bi2Te3/Bi2–xSbxTe3 by pulsed potentiostatic electrodeposition from single bath acidic aqueous electrolyte over cm2 area. Cyclic...
We examined the thermal conductivity of (Bi${}_{2}$)${}_{m}$-(Bi${}_{2}$Te${}_{3}$)${}_{n}$ alloys, which are composed alternating sequences Bi${}_{2}$ and Bi${}_{2}$Te${}_{3}$ structural units. The phonon these alloys was sharply reduced relative to that elemental Bi for temperatures below 100 K. Our measurements suggested defects reduce in materials. Using Debye-Callaway model heat transport, we link this point defects.
We report synchrotron x-ray scattering studies of charge/orbitally ordered (COO) nanoclusters in Nd$_{0.7}$Sr$_{0.3}$MnO$_3$. find that the COO are strongly suppressed an applied magnetic field, and their decreasing concentration follows field-induced decrease sample electrical resistivity. The nanoclusters, however, do not completely disappear conducting state, suggesting this state is inhomogeneous contains admixture insulating phase. Similar results were also obtained for zero-field...
Uniform metal contacts are critical for advanced thermoelectric devices. The uniformity of the contact resistance gold, tungsten, and SrRuO3 electrodes on polycrystalline ternary Bi2Te3-based alloys different types surface cleaning procedures was characterized. presence a nanometer-thick native oxide layer Bi2Te3 leads to large non-uniform resistance. Surface treatments included solvent cleans chemical dry etching prior metallization Bi2Te3. Only led significant improvement in uniformity....