105 research outputs found
Nanoscale Electrostatic Control of Oxide Interfaces
We develop a robust and versatile platform to define nanostructures at oxide
interfaces via patterned top gates. Using LaAlO/SrTiO as a model
system, we demonstrate controllable electrostatic confinement of electrons to
nanoscale regions in the conducting interface. The excellent gate response,
ultra-low leakage currents, and long term stability of these gates allow us to
perform a variety of studies in different device geometries from room
temperature down to 50 mK. Using a split-gate device we demonstrate the
formation of a narrow conducting channel whose width can be controllably
reduced via the application of appropriate gate voltages. We also show that a
single narrow gate can be used to induce locally a superconducting to
insulating transition. Furthermore, in the superconducting regime we see
indications of a gate-voltage controlled Josephson effect.Comment: Version after peer review; includes additional data on
superconductivit
Superconducting quantum point contact with split gates in the two dimensional LaAlO3/SrTiO3 superfluid
One of the hallmark experiments of quantum transport is the observation of
the quantized resistance in a point contact formed with split gates in
GaAs/AlGaAs heterostructures. Being carried out on a single material, they
represent in an ideal manner equilibrium reservoirs which are connected only
through a few electron mode channel with certain transmission coefficients. It
has been a long standing goal to achieve similar experimental conditions also
in superconductors, only reached in atomic scale mechanically tunable break
junctions of conventional superconducting metals, but here the Fermi wavelength
is so short that it leads to a mixing of quantum transport with atomic orbital
physics. Here we demonstrate for the first time the formation of a
superconducting quantum point contact (SQPC) with split gate technology in a
superconductor, utilizing the unique gate tunability of the two dimensional
superfluid at the LaAlO3/SrTiO3 (LAO/STO) interface. When the constriction is
tuned through the action of metallic split gates we identify three regimes of
transport: (i) SQPC for which the supercurrent is carried only by a few quantum
transport channels. (ii) Superconducting island strongly coupled to the
equilibrium reservoirs. (iii) Charge island with a discrete spectrum weakly
coupled to the reservoirs. Our experiments demonstrate the feasibility of a new
generation of mesoscopic all-superconductor quantum transport devices.Comment: 18 page
Effects of Rapid Heating on Solutionizing Characteristics of Al-Si-Mg Alloys Using a Fluidized Bed
Effects of rapid heat transfer using a fluidized bed on the heat-treating response of Al-Si-Mg alloys (both unmodified and Sr modified) were investigated. The heating rate in the fluidized bed is greater than in conventional air convective furnaces. Particle size analyses of eutectic Si showed that the high heating rate during fluidized bed solution heat treatment causes faster fragmentation and spherodization of Si particles compared to conventional air convective furnaces. The mechanism of Si fragmentation through fluidized bed processing is through both brittle fracture and neck formation and its propagation. In contrast to this, the mechanism of Si fragmentation using a conventional air convective furnace is through neck formation and propagation. The Sr-modified D357 alloy showed a faster spherodizing rate than the unmodified alloy. Thermal analyses showed an exothermic reaction during solution heat treatment using a fluidized bed due to recrystallization, and coarsening of eutectic Al grains. Whereas the alloy solutionized using a conventional air convective furnace showed two exothermic reactions, one due to annihilation of point defects and the other due to recrystallization, and coarsening of the eutectic grains in the aluminum matrix. The recrystallization temperature of the alloy solutionized in the fluidized bed is lower than those in the conventional air convective furnace. Both tensile strength and elongation of fluidized bed solutionized alloys are greater than those solutionized using the air convective furnace. The optimum heat-treatment time for T4 temper using a fluidized bed for unmodified and Sr-modified alloy was reduced to 60 and 30 minutes, respectively
Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy
Antibiotics are not needed during tube thoracostomy for spontaneous pneumothorax: an observational case study
Strength-ductility behaviour of Al-Si-Cu-Mg casting alloys in T6 temper
A comparative study of the mechanical properties of 20 experimental alloys has been carried out. The effect of different contents of Si, Cu, Mg, Fe and Mn, as well as solidification rate, has been assessed using a strength-ductility chart and a quality index-strength chart developed for the alloys. The charts show that the strength generally increases and the ductility decreases with an increasing content of Cu and Mg. Increased Fe (at Fe/Mn ratio 0.5) dramatically lowers the ductility and strength of low Si alloys. Increased Si content generally increases the strength and the ductility. The increase in ductility with increased Si is particularly significant when the Fe content is high. The charts are used to show that the cracking of second phase particles imposes a limit to the maximum achievable strength by limiting the ductility of strong alloys. The (Cu + Mg) content (at.%), which determines the precipitation strengthening and the volume fraction of Cu-rich and Mg-rich intermetallics, can be used to select the alloys for given strength and ductility, provided the Fe content stays below the Si-dependent critical level for the formation of pre-eutectic alpha-phase particles or beta-phase plates
The accuracy of 18F-Florodeoxyglucose Positron Emission Tomography /Computed Tomography in the evaluation of bone lesions of undetermined origin
Silicon nanowire network metal-semiconductor-metal photodetectors
Cataloged from PDF version of article.We report on the fabrication and characterization of solution-processed, highly flexible, silicon nanowire network based metal-semiconductor-metal photodetectors. Both the active part of the device and the electrodes are made of nanowire networks that provide both flexibility and transparency. Fabricated photodetectors showed a fast dynamic response, 0.43 ms for the rise and 0.58 ms for the fall-time, with a decent on/off ratio of 20. The effect of nanowire-density on transmittance and light on/off behavior were both investigated. Flexible photodetectors, on the other hand, were fabricated on polyethyleneterephthalate substrates and showed similar photodetector characteristics upon bending down to a radius of 1 cm. © 2013 AIP Publishing LLC
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