Vincent P. LaBella

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We report a large spin-polarized current injection from a ferromagnetic metal into a nonferromagnetic semiconductor, at a temperature of 100 Kelvin. The modification of the spin-injection process by a nanoscale step edge was observed. On flat gallium arsenide [GaAs(110)] terraces, the injection efficiency was 92%, whereas in a 10-nanometer-wide region(More)
The reconstructions of the InP~001! surface prepared by molecular beam epitaxy have been studied with in situ reflection high-energy electron diffraction ~RHEED! and scanning tunneling microscopy ~STM!. The growth chamber contains a highly accurate temperature measurement system and uses a solid-source, cracked phosphorus, valved effusion cell. Five(More)
The atomic arrangement of the technologically important As-rich GaAs 001 2 3 4 reconstructed surface is determined using bias-dependent scanning tunneling microscopy (STM) and first-principles electronic structure calculations. The STM images reveal the relative position and depth of the atomicscale features within the trenches between the top-layer As(More)
The migration of individual Ga atoms on the technologically important GaAs~001!-(234) reconstructed surface has been studied as a function of substrate temperature and As4 pressure using a combined molecular beam epitaxy and scanning tunneling microscope ultrahigh vacuum multichamber facility. We have deposited 10% of a plane of Ga onto a GaAs~001! surface(More)
Preroughening and roughening transitions are observed on the GaAs(001) surface using scanning tunneling microscopy. By tuning the substrate temperature or As4 pressure the surface morphology can be made free of islands, covered with one monolayer high islands or covered with islands on top of islands forming a wedding-cake-type structure. These three(More)
Mn concentration depth profiles in Mn-doped GaAs thin films grown at substrate temperatures of 580 and 250 °C using various Mn cell temperatures have been investigated with dynamic secondary ion mass spectrometry and Auger electron spectroscopy. When the samples are grown at a low substrate temperature of 250 °C, the Mn distributes uniformly. For the(More)
Mn doped GaAs thin films were grown using molecular beam epitaxy at high and low substrate temperatures. The elemental concentration depth profiles in the thin films were determined by using Auger electron spectroscopy combined with ion etching. The Mn concentration is higher near the surface and then decreases with depth for films grown at high substrate(More)
The dynamics of a random distribution of spontaneously formed 2D GaAs islands are studied using scanning tunneling microscopy. The equilibrium concentration of islands is easily tuned from 0% to 50% coverage by only changing the As4 overpressure. Images taken during the early stages of island formation reveal the roughening transition primarily occurs(More)
The research group at the University of Arkansas is interested in the surface physics of fabricating III-V semiconductor structures such as GaAs and InP. We are particularly interested in the fundamental properties, such as template structure, diffusion, nucleation and growth. The techniques used are STM, MBE, RHEED, Xray diffraction, and Hall effect(More)
Ilona Sitnitsky, John J. Garramone, and Joseph Abel College of Nanoscale Science and Engineering, University at Albany, SUNY, Albany, New York 12203 Peng Xu, Steven D. Barber, Matt L. Ackerman, J. Kevin Schoelz, and Paul M. Thibado Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 Vincent P. LaBella College of Nanoscale Science and(More)
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