A5080109854- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Laser Design and Applications
- Wind and Air Flow Studies
- Electron and X-Ray Spectroscopy Techniques
- Semiconductor Lasers and Optical Devices
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Surface and Thin Film Phenomena
- Advanced Semiconductor Detectors and Materials
- Photonic and Optical Devices
- Advanced Chemical Physics Studies
- solar cell performance optimization
- Solid State Laser Technologies
- Ion-surface interactions and analysis
- Graphene research and applications
- Laser-induced spectroscopy and plasma
- Integrated Circuits and Semiconductor Failure Analysis
- Meteorological Phenomena and Simulations
- Astro and Planetary Science
- Spectroscopy and Quantum Chemical Studies
- Planetary Science and Exploration
- GaN-based semiconductor devices and materials
- Ocular and Laser Science Research
Clark Atlanta University
2007-2024
Stanford University
1983-2024
SLAC National Accelerator Laboratory
2024
Usmanu Danfodiyo University
2023
Hiden Analytical (United Kingdom)
2020
Georgia State University
2020
Los Alamos National Laboratory
1995-2019
O'Brien Institute
2009-2017
The University of Melbourne
2009-2017
St Vincent's Hospital
2009-2017
This paper reports detailed molecular beam measurements of the sticking coefficient at zero coverage for O2 on a Pt(111) surface as function initial energy (Ei), angle incidence (θi), and temperature (Ts). Under most conditions measures probability dissociative chemisorption. These results demonstrate that both precursor mediated quasi-direct dissociation can be observed, depending upon conditions. The process is revealed by step increase in with Ei. feature scales intermediately between Ei...
Molecular beam techniques have been utilized to measure the dissociative chemisorption probability at zero surface coverage S0 for D2(H2) on Pt(111) as a function of initial energy Ei, angle incidence θi, temperature Ts, isotopic mass and nozzle Tn. shows large increase with translational energy, but no threshold in peaking θi=0°, an independence isotope These results are interpreted terms direct terraces. The dynamical picture that emerges is although there significant barrier dissociation...
We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate ∼1 µm/h with control silicon doping concentration from 5 × 1016 1019 cm−3. In S-MBE, pre-oxidized gallium in form molecular beam that is 99.98% Ga2O, i.e., suboxide, supplied. Directly supplying Ga2O surface bypasses rate-limiting first step two-step reaction mechanism involved by conventional MBE. As result, readily achieved relatively low temperature (Tsub ≈ 525 °C), resulting films high...
We report here a systematic study of the electrical properties large number metal/n-type GaAs (Cr, Mn, Sn, Ni, Al, Pd, Cu, Ag, Au) diodes. Diodes were fabricated on cleaved GaAs(110) surfaces under ultrahigh-vacuum conditions with in situ metal deposition. Using current-voltage (I-V) and capacitance-voltage (C-V) measuring techniques, we able to obtain very reliable consistent determinations barrier height ${\ensuremath{\varphi}}_{b}$ ideality factor n. All metal-semiconductor systems formed...
Strain-engineering is a powerful means to tune the polar, structural, and electronic instabilities of incipient ferroelectrics. KTaO3 near polar instability shows anisotropic superconductivity in electron-doped samples. Here, we demonstrate growth high-quality thin films by molecular-beam epitaxy. Tantalum was provided either suboxide source emanating TaO2 flux from Ta2O5 contained conventional effusion cell or an electron-beam-heated tantalum source. Excess potassium combination ozone...
An in-depth comparison of plume calculations from the Quick Urban and Industrial Complex (QUIC) dispersion model to street- roof-level concentration measurements for a daytime night time release taken during Joint 2003 field experiment held in downtown Oklahoma City is presented. A number improvements empirical-diagnostic wind solver better account high-rise buildings dense urban areas will be discussed. Traditional statistical performance measures reveal that code performing as well...
A volumetric direct nuclear-pumped laser has been achieved for the first time by using 3He(n,p)3H reaction to excite a 3He-Ar laser. Lasing was at 1.79 μ in Ar I total pressures ranging from 200 700 Torr with 10% Ar, demonstrating stable high-pressure lasing. Laser energy output increased both increasing pressure and thermal neutron flux.
In in vivo tissue engineering, many implanted cells die because of hypoxic conditions immediately postimplantation. The aim this study was to determine whether delayed myoblast implantation, at day 4 or 7, improves survival compared with implantation 0 an arterio-venous loop (AB loop) chamber model. adult inbred Sprague-Dawley rats, AB inserted into a plastic (day 0). Group I, 0, two million DiI-labeled (neonatal inbred) myoblasts were around the loop. Groups II and III, created novel cell...
Captured the photo-induced loss of planarity which enables o -nitrophenol to undergo non-radiative relaxation.
Fluorination of graphene has emerged as an attractive approach toward manipulating its physical, chemical, and electronic properties. To this end, we have demonstrated the viability sulfur hexafluoride plasmas to fluorinate a safer alternative commonly reported techniques fluorination that include exposures fluorine xenon difluoride gas. Incorporation moieties on after SF6 plasma-treatment was confirmed by x-ray photoelectron spectroscopy. Modifications in valence band states were...
We have prepared [3H]dolastatin 10 and examined its interactions with tubulin. Binding kinetics appeared to be biphasic, a rapid initial reaction that could not accurately measured, followed by slower second reaction. Bound drug was stable in centrifugal gel filtration, column high performance liquid chromatography but the bound displaced an active isomer of dolastatin 10. Scatchard analysis binding data consistent two classes sites. However, induced aggregation upon tubulin, complicating...
Previous strain-relief p-i-n InGaAs-GaAs quantum well (qw) modulators have incurred surface striations upon growth due to defect formation, resulting in an optically rough surface. We present here a qw modulator on GaAs substrate with InGaAs wells and GaAsP barriers which balance the strain so that lattice does not relax, leading much fewer defects, smooth obtain transmission change from 60% 80% at 1014 nm for sample 1 μm thick intrinsic region.
Previously a donor defect level at about −0.1 eV below the conduction band minimum has been associated with InP, in part to explain nonmonotonic movement of Fermi within gap during oxidation n-InP. We present here new soft x-ray photoemission spectroscopy results which associate this behavior oxide on surface InP rather than native such as P vacancy. Specifically, we have observed that reversal occurs exactly same oxygen exposure appearance structure In 4d core line indicative formation (s)....
The mechanism of Schottky barrier formation on GaAs and other semiconductors seems to be getting more, rather than less, controversial. Therefore, it is important examine new data as becomes available. Four types will mentioned. emphasis (1) the metal–GaAs chemical reaction products at interface their correlation (or lack thereof) with heights (2) evidence for discontinuity in height one goes from photoemission spectroscopy (PES) pinning results (thickness order 1–1000 Å metal films). Also...
The initial sticking coefficient (probability for dissociative chemisorption) has been measured O2 on a Pt(111) surface as function of energy, incident angle, and temperature using molecular beam techniques. results reveal two distinct mechanisms sticking; precursor mediated direct dissociation, either which can dominate depending upon the adsorption conditions.
Using valence-band and core-level photoemission spectroscopy (PES) electrical device measurements, the effects of annealing Ag, Al, Au on n-type (110)GaAs Schottky diodes fabricated in ultrahigh vacuum have been studied. PES was used to monitor annealing-induced changes interface Fermi level position chemical nature metal–semiconductor for submonolayer several monolayer coverages. Barrier height determinations were also performed using current–voltage (I–V) capacitance–voltage (C–V)...
Nuclear-pumped lasing of Ar-Xe and He-Xe has been demonstrated using 235UF6 fission-fragment excitation. Fission fragments were created by absorption thermal neutrons in a combination gaseous laser-tube wall coatings formed from UF6 chemical reaction products. At pressure 600 Torr Ar–(3%) Xe, occurred at 2.65 μm Xe. Up to 3 was added before serious laser quenching occurred. With added, 38% the energy deposition came remainder uranium coating. The neutron flux threshold found be 4×1015 n/cm2 sec.
The room-temperature growth of the Pd/n-GaAs (110) intimate interface has been studied by soft x-ray core level photoemission spectroscopy. It is shown that Pd reacts with GaAs surface forming an arsenide compound in which phase segregated Ga metal included. In addition some As on this composite. Using deconvolution different contributions, Schottky barrier height system experimentally determined to be 0.9±0.05 eV. pinning attributed deeper unified defect model.
We show by application to Si that polarimetric measurements on radiation reflected nonspecularly from rough surfaces can distinguish between geometric-optics (facet or tangent-plane) and Rayleigh-Fano (random diffraction grating) scattering models, thus providing new details about surface roughness. A class of macroscopically but microscopically smooth is found gives accurate specular ellipsometric data while being unsuitable for reflectance measurements.
We have studied the electronic characteristics of multilayer epitaxial graphene under a perpendicularly applied electric bias. Ultraviolet photoemission spectroscopy measurements reveal that there is notable variation density-of-states in valence bands near Fermi level. Evolution structure graphite and rotational-stacked as function bias investigated using first-principles density-functional theory including interlayer van der Waals interactions. The experimental theoretical results...
The Quick Urban and Industrial Complex (QUIC) plume modeling system is used to explore how the transport dispersion of vehicle emissions in cities are impacted by presence buildings. Using downtown Philadelphia as a test case, notional gases particles specified line source releases on subset east–west north–south streets. Cases were run flat terrain with 3D buildings present order show differences model-computed outdoor concentration fields without present. QUIC calculations that result...
The room-temperature interaction of Ni overlayers with cleaved GaAs(110) and InP(110) is investigated valence-band core-level soft x-ray photoemission spectroscopies. It shown that reacts strongly both substrates leading to the formation phosphides or arsenides segregation metallic components. At room temperature a reacted-phase interlayer several A\r{} formed, followed by lateral layers nonreacted Ni. In case Ni/GaAs interface reaction less pronounced. Some other spectroscopic features...