A5056358886- Carbon Nanotubes in Composites
- GaN-based semiconductor devices and materials
- Graphene research and applications
- Nanowire Synthesis and Applications
- Mechanical and Optical Resonators
- Semiconductor materials and devices
- Molecular Junctions and Nanostructures
- Advanced Thermoelectric Materials and Devices
- Semiconductor materials and interfaces
- Force Microscopy Techniques and Applications
- nanoparticles nucleation surface interactions
- Advancements in Semiconductor Devices and Circuit Design
- Metal-Organic Frameworks: Synthesis and Applications
- Gas Sensing Nanomaterials and Sensors
- Photonic and Optical Devices
- Advanced Memory and Neural Computing
- Surface and Thin Film Phenomena
- Thermal properties of materials
- Quantum and electron transport phenomena
- Ga2O3 and related materials
- Machine Learning in Materials Science
- Neutrino Physics Research
- Advanced Electrical Measurement Techniques
- Semiconductor Quantum Structures and Devices
- Nanotechnology research and applications
Sandia National Laboratories California
2015-2024
University of Liège
2024
Hydro-Québec
2000-2023
Sandia National Laboratories
2013-2023
Carleton University
2011-2022
Laboratoire de Conception Fabrication Commande
2011-2019
ParisTech
2011-2018
Université de Lorraine
2018
Lawrence Livermore National Security
2017-2018
École nationale supérieure d'arts et métiers
2011-2012
Guests for Conductors Thin films of metal-organic framework (MOF) compounds are generally poor conductors because the linking organic groups usually insulators with little π-orbital conjugation. Talin et al. (p. 66 , published online 5 December) show that infiltrating copper-based MOF HKUST-1 conjugated molecule 7,7,8,8-tetracyanoquinododimethane created an air-stable material conductivities as high 7 siemens per meter.
Based on the concept of band bending at metal/semiconductor interfaces as an energy filter for electrons, we present a theory enhancement thermoelectric properties semiconductor materials with metallic nanoinclusions. We show that Seebeck coefficient can be significantly increased due to strongly energy-dependent electronic scattering time. By including phonon scattering, find $ZT$ electron is important high doping, while low doping it primarily decrease in thermal conductivity.
Carbon nanotubes (CNTs) are amongst the most explored one-dimensional nanostructures and have attracted tremendous interest from fundamental science technological perspectives. Albeit topologically simple, they exhibit a rich variety of intriguing electronic properties, such as metallic semiconducting behaviour. Furthermore, these structures atomically precise, meaning that each carbon atom is still three-fold coordinated without any dangling bonds. CNTs been used in many laboratories to...
Nonvolatile redox transistors (NVRTs) based upon Li-ion battery materials are demonstrated as memory elements for neuromorphic computer architectures with multi-level analog states, "write" linearity, low-voltage switching, and low power dissipation. Simulations of backpropagation using the device properties reach ideal classification accuracy. Physics-based simulations predict energy costs per operation <10 aJ when scaled to 200 nm × nm.
We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed an exposure 32.5 kg-yr, background ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1\sigma$ region interest. This sets lower limit half-life $T_{1/2}^{0\nu\beta\beta}$($^{136}$Xe) > 1.6 10$^{25}$ (90% CL), corresponding to effective Majorana masses less than 140-380 meV, depending matrix element calculation.
A new thermoelectric material with high Seebeck coefficient and low thermal conductivity is demonstrated based on an electrically conducting metal–organic framework (MOF) using the [email protected] concept. This demonstration opens a avenue for future development of materials. As service to our authors readers, this journal provides supporting information supplied by authors. Such materials are peer reviewed may be re-organized online delivery, but not copy-edited or typeset. Technical...
Terahertz (THz) technologies are promising for diverse areas such as medicine, bioengineering, astronomy, environmental monitoring, and communications. However, despite decades of worldwide efforts, the THz region electromagnetic spectrum still continues to be elusive solid state technology. Here, we report on development a powerless, compact, broadband, flexible, large-area, polarization-sensitive carbon nanotube detector that works at room temperature. The is sensitive throughout entire...
At semiconductor-metal junctions, the Schottky barrier height is generally fixed by "Fermi-level pinning." We find that when a semiconducting carbon nanotube end contacted to metal (the optimal geometry for nanodevices), behavior radically different. Even Fermi level fully "pinned" at interface, turn-on voltage expected an unpinned junction. Thus threshold may be adjusted device performance, which not possible in planar contacts. Similar heterojunctions between nanotubes and semiconductors.
We calculate the properties of $p\ensuremath{-}n$ junctions, $n\ensuremath{-}i$ and Schottky barriers made on a single-wall carbon nanotube. In contrast to planar bulk depletion width for nanotubes varies exponentially with inverse doping. addition, there is very long-range (logarithmic) tail in charge distribution, extending over entire tube. These effects can render traditional devices unworkable, while opening new possibilities device design. Our general conclusions should apply broad...
This study examines children's efforts to make sense of new mathematics instruction. The documents major categories errors that appear consistently as children learn decimal fractions. It then establishes the conceptual sources these errors. Whole number derive from applying rules for interpreting multidigit integers. Fraction interpret decimals Different curriculum sequences influence probability classes will appear. is suggested are a natural concomitant students' attempts integrate...
We report the observation of two-neutrino double-beta decay in Xe-136 with T_1/2 = 2.11 +- 0.04 (stat.) 0.21 (sys.) x 10^21 yr. This second order process, predicted by Standard Model, has been observed for several nuclei but not Xe-136. The rate provides new input to matrix element calculations and search more interesting neutrino-less decay, most sensitive probe existence Majorana particles measurement neutrino mass scale.
Metal-organic frameworks (MOFs) are crystalline nanoporous materials comprised of organic electron donors linked to metal ions by strong coordination bonds. Applications such as gas storage and separations currently receiving considerable attention, but if the unique properties MOFs could be extended electronics, magnetics, photonics, impact on material science would greatly increase. Recently, we obtained "emergent properties," electronic conductivity energy transfer, infiltrating MOF pores...
We report on an improved measurement of the $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ half-life ${}^{136}$Xe performed by EXO-200. The use a large and homogeneous time-projection chamber allows for precise estimate fiducial mass used measurement, resulting in small systematic uncertainty. also discuss detail data-analysis methods double-$\ensuremath{\beta}$ decay searches with EXO-200, while emphasizing those directly related to present measurement. is found be...
Photodetectors play key roles in many applications such as remote sensing, night vision, reconnaissance, medical imaging, thermal and chemical detection. Several properties performance, reliability, ease of integration, cost, weight, form factor are all important determining the attributes photodetectors for particular applications. While a number materials have been used over past several decades to address photodetection needs across electromagnetic spectrum, advent nanomaterials opens...
The current-voltage characteristics of thin wires are often observed to be nonlinear, and this behavior has been ascribed Schottky barriers at the contacts. We present electronic transport measurements on GaN nanorods demonstrate that nonlinear originates instead from space-charge-limited current. A theory current in corroborates experiments shows poor screening high-aspect ratio materials leads a dramatic enhancement space-charge limited current, resulting new scaling terms aspect ratio.
We demonstrate an optically active nanotube-hybrid material by functionalizing single-wall nanotubes with azo-based chromophore. Upon UV illumination, the conjugated chromophore undergoes a cis-trans isomerization leading to charge redistribution near nanotube. This changes local electrostatic environment, shifting threshold voltage and increasing conductivity of nanotube transistor. For $\ensuremath{\sim}1%--2%$ coverage, we measure shift in up 1.2 V. Further, conductance change is...
Transition metal dichalcogenides (TMDs) have emerged as a new class of two-dimensional materials that are promising for electronics and photonics. To date, optoelectronic measurements in these shown the conventional behavior expected from photoconductors such linear or sublinear dependence photocurrent on light intensity. Here, we report observation regime operation where depends superlinearly We use spatially resolved devices consisting CVD-grown monolayers TMD alloys spanning MoS2 to MoSe2...
Photovoltaic devices using GaAs nanopillar radial p–n junctions are demonstrated by means of catalyst-free selective-area metal–organic chemical vapor deposition. Dense, large-area, lithographically defined vertical arrays nanowires with uniform spacing and dimensions allow for power conversion efficiencies this material system 2.54% (AM 1.5 G) high rectification ratio 213 (at ±1 V). The absence metal catalyst contamination results in leakage currents ∼236 nA at −1 V. High-resolution...
Increasing performance demands on photodetectors and solar cells require the development of entirely new materials technological approaches. We report fabrication optoelectronic characterization a photodetector based optically-thick films dense, aligned, macroscopically long single-wall carbon nanotubes. The exhibits broadband response from visible to mid-infrared under global illumination, with time less than 32 μs. Scanning photocurrent microscopy indicates that signal originates at...
Light polarization is used in the animal kingdom for communication, navigation, and enhanced scene interpretation also plays an important role astronomy, remote sensing, military applications. To date, there have been few photodetector materials demonstrated to direct sensitivity, as usually case nature. Here, we report realization of a carbon-based broadband photodetector, where polarimetry intrinsic active material. The detector based on p-n junctions formed between two macroscopic films...
EXO-200 is an experiment designed to search for double beta decay of $^{136}$Xe with a single-phase, liquid xenon detector. It uses active mass 110 kg enriched 80.6% in the isotope 136 ultra-low background time projection chamber capable simultaneous detection ionization and scintillation. This paper describes detector particular attention most innovative aspects design that revolve around reduction backgrounds, efficient use expensive isotopically xenon, optimization energy resolution...
Understanding the limits of spatiotemporal carrier dynamics, especially in III-V semiconductors, is key to designing ultrafast and ultrasmall optoelectronic components. However, identifying such properties controlling them has been elusive. Here, using scanning electron microscopy, bulk n-GaAs p-InAs, we simultaneously measure picosecond dynamics along with three related quantities: subsurface band bending, above-surface vacuum potentials, surface trap densities. We make two unexpected...
Metal-semiconductor contacts play a key role in electronics. Here we show that for quasi-one-dimensional (Q1D) structures such as nanotubes and nanowires, side contact with the metal only leads to weak band realignment, contrast bulk metal-semiconductor contacts. Schottky barriers are much reduced compared limit, should facilitate formation of good However, conventional strategy heavily doping semiconductor obtain Ohmic breaks down nanowire diameter is reduced. The issue Fermi level pinning...