Search

Using an InAs/GaSb composite quantum well, we demonstrate an enhancement mode single electron transistor. With a Hall bar geometry, we show that the device undergoes a transition from accumulation of two-dimensional (2D) holes in GaSb to a complete depletion and finally to an inversion layer of 2D electrons in InAs. When the top-gate area is reduced to nanometer scale, the inversion electrons are confined to a quantum dot, and the transistor displays single electron characteristics: a series of conductance peaks resulting from electrons tunnelling through the quantum dot. The occurrence of the first peak is the signature of one electron occupying InAs quantum dot. The unique configuration of enhancement quantum dots makes it possible to upscale to 2D arrays for manipulation and transporting of single spins.

We demonstrate experimentally single-electron quantum dots using a single-top-gate transistor configuration on a composite quantum well. The data indicate a 15 meV Coulomb charging energy and a 20 meV orbital energy spacing, which imply a quantum dot of 20 nm in diameter. Combining with the inherent advantage of a large electron g(*) factor in InAs, our demonstration is significant for a solid state implementation of a scalable quantum computing. (c) 2006 American Institute of Physics.

We demonstrate experimentally single-electron quantum dots using a single-top-gate transistor configuration on a composite quantum well. The data indicate a 15 meV Coulomb charging energy and a 20 meV orbital energy spacing, which imply a quantum dot of 20 nm in diameter. Combining with the inherent advantage of a large electron g* factor in InAs, our demonstration is significant for a solid state implementation of a scalable quantum computing, Published in Applied Physics Letters, v88 article ID 192102, 8 May 2006.

The authors demonstrate a silicon-based single-electron transistor (SET) in the few-electron regime. Our structure is similar to a metal-oxide-semiconductor field-effect transistor. The substrate, however, is undoped and could be isotope enriched so that any nonuniformity and spin decoherence due to impurity and nuclear spins can be minimized. A bilayer-gated configuration provides flexibility in manipulating single electrons. The stability chart measured at 4.2 K shows diamondlike domains with a charging energy of 18 meV, indicating a quantum dot of 20 nm in diameter. The benefits of using this enhancement-mode SET in silicon and its potential application for scalable quantum computing are discussed., Published in Applied Physics Letter, v89 article ID 073106, 16 Aug 2006. Prepared in collaboration with the National Institute of Standards and Technology, Gaithersburg, MD. Prepared in cooperation with the Department of Electrical and Computer Engineering, University of Maryland, College Park.

We report experimental results on gated Y-branch switches made from InAs ballistic electron waveguides. We demonstrate that gating modifies the electron wave functions as well as their interference pattern, resulting in anticorrelated oscillatory transconductances. Our data provide evidence of steering the electron wave function in a multichannel transistor structure. (C) 2005 American Institute of Physics.

This report discusses procedures for the extrapolation of low-strain seismic measurements made at a specific site to predict the site response under earthquake loading conditions. Because of the non-linear relation between stress and strain exhibited by soils at strain levels exceeding about 0.000001, a program to determine dynamic soil properties at low to high strain levels and at different depths in the soil column at the site is required. Utilizing recent advances in field measurement techniques, this goal can be best accomplished with a combination of in situ geophysical methods, including surface reflection and refraction methods; cross-hole and down-hole techniques utilizing impulsive and vibratory sources; and dynamic loading methods involving monitoring of in-place deformation. Knowledge of the variation with strain level and other factors of equivalent moduli and damping at a site may enable frequency-dependent scaling rules to be developed for the computation of high-strain response from microseismic response curves. This procedure can be evaluated by performing field measurements at sites for which comprehensive strong motion data bases are already available. Keywords: Modulus of elasticity. (Author)

Let X sub 1, X sub 2,..., X sub n be an ordered sample from the standard normal population. If the r largest and r smallest observations are omitted, the range of the remaining n-2r sample values is defined as the rth quasi-range. Expressions involving multivariate normal probabilities are found for the density function, the cumulative distribution function, and the expected value. The midrange is defined. If the sample values X sub 1 and X sub n are from the standard normal population, it is possible to express the density function of the midrange in terms of multivariate normal probabilities for even values of n. (Author), Report on 'Themis Signal Analysis Statistics Research Program.' Sponsored in part by National Institutes of Health.