Precipitation of hydrogen in crystalline silicon

1988 ◽  
Vol 46 ◽  
pp. 476-477
Author(s):  
F. A. Ponce ◽  
N. M. Johnson
Keyword(s):  
Electrical Activity ◽  
Single Crystals ◽  
Crystalline Silicon ◽  
Deep Level ◽  
Shallow Donor ◽  
Time Intervals ◽  
Shallow Acceptor ◽  
Optical Isolation ◽  
Direct Exposure

The behavior of hydrogen in semiconductors has been a topic of increasing interest in recent years. The interest is in part stimulated by the ability of hydrogen to remove the electrical activity (passivate) of both dopant impurities and deep-level defects at moderate temperatures (<300C). Hydrogen is known to readily diffuse in silicon resulting in the neutralization of shallow-acceptor and shallow-donor dopants, Controlled studies of the role of hydrogen in silicon has been recently reported. This was achieved by exposing silicon single crystals to monoatomic hydrogen or deuterium from a microwave gas discharge. To prevent the radiation damage that results from direct exposure to the plasma, the specimens were mounted on a hot stage that was located down stream from the plasma. Optical isolation was achieved with the use of baffles. The specimen temperature was held constant in the range of 100-400°C for time intervals between 10-120 minutes.

Hydrogen in III–V Semiconductors

1987 ◽  
Vol 104 ◽  
Author(s):  
W. C. Dautremont–Smith
Keyword(s):  
Hydrogen Diffusion ◽  
Deep Level ◽  
Bulk Material ◽  
Low Frequency ◽  
Shallow Donor ◽  
Direct Exposure ◽  
Donor And Acceptor ◽  
Absorption Studies ◽  
Dx Center ◽  
P Type

ABSTRACTThe reversible introduction of atomic hydrogen into III–V semiconductors reduces the active concentrations of shallow donor and acceptor levels, as well as a variety of deep levels. Dissociation of the hydrogen-containing complexes by thermal annealing can restore the original active concentrations, and aid in the characterization of the complexes involved. Hydrogen is in-diffused at temperatures typically in the 150 to 300°C range, most simply from an H2 plasma.In GaAs, the III–V compound which has been subjected to the most hydrogenation studies, carrier concentrations are reduced (by up to many orders of magnitude) in both n- and p-type material. Hydrogen diffusion depths are dependent on dopant concentration, but for similar doping levels, diffusion is always deeper into p-type GaAs. In addition, the type of plasma exposure strongly influences the depth of H diffusion, with low frequency, direct exposure producing the greatest penetration depth. A variety of deep level defects in bulk material (including EL2) and in MBE-grown layers can be passivated, and partial passivation of interface-related defects in GaAs-on-Si has been demonstrated. Reactivation kinetics are dependent on the nature of the dopant or defect, with the passivation of p-GaAs being less stable than that of n-GaAs. Recent infra-red absorption studies have confirmed the formation of a donor-hydrogen complex in n-GaAs, in contrast to an As-H complex in p-GaAs. In GaAIAs, acceptors, donors, and the DX center have been passivated. In some cases, the defect passivation has greater thermal stability than that of the shallow levels, a property of potential benefit. Recently demonstrated applications of hydrogenation include an MBE GaAs MESFET with a hydrogenated channel, and a GaAs/GaAIAs double heterostructure laser with current guiding provided by resistive hydrogenated regions.

Tailoring the Electrical Properties of Undoped GaP

2011 ◽  
Vol 178-179 ◽  
pp. 410-415 ◽  
Author(s):  
Pawel Kaminski ◽  
Roman Kozlowski ◽  
Stanislawa Strzelecka ◽  
Andrzej Hruban ◽  
Elzbieta Jurkiewicz-Wegner ◽  
...  
Keyword(s):  
Deep Level ◽  
Experimental Studies ◽  
Charge Compensation ◽  
Shallow Donor ◽  
Residual Concentration ◽  
Charge Neutrality ◽  
Shallow Acceptor ◽  
Acceptor Concentration ◽  
Defect Centers ◽  
Transient Spectroscopy

The charge compensation in undoped GaP single crystals is investigated by modeling the Fermi level position for various concentrations of shallow and deep donors and acceptors. The model is based on the numerical solution of the charge neutrality equation and allows for calculating the Fermi energy in the temperature range of 1 –1000 K. The experimental studies of the electronic properties and concentrations of grown-in defect centers are performed by the high-resolution photoinduced transient spectroscopy (HRPITS). We show that at the shallow acceptor concentration below 1x1015 cm-3 and the concentration of deep-level defects ~3x1015 cm-3 obtaining undoped GaP with the semi-insulating (SI) properties is possible by substantial reducing the residual concentration of shallow donor impurities.

The Role of Computer Modeling in Electrocardiography

1990 ◽  
Vol 29 (04) ◽  
pp. 282-288 ◽  
Author(s):  
A. van Oosterom
Keyword(s):  
Electrical Activity ◽  
Computer Modeling ◽  
Body Surface ◽  
Electrical Current ◽  
The Body ◽  
Volume Conductor ◽  
Current Generator ◽  
Cardiac Electrical Activity ◽  
Source Models

AbstractThis paper introduces some levels at which the computer has been incorporated in the research into the basis of electrocardiography. The emphasis lies on the modeling of the heart as an electrical current generator and of the properties of the body as a volume conductor, both playing a major role in the shaping of the electrocardiographic waveforms recorded at the body surface. It is claimed that the Forward-Problem of electrocardiography is no longer a problem. Several source models of cardiac electrical activity are considered, one of which can be directly interpreted in terms of the underlying electrophysiology (the depolarization sequence of the ventricles). The importance of using tailored rather than textbook geometry in inverse procedures is stressed.

Role of Histamine and Leucotaxin in Function of Cellular Defense Mechanism

1956 ◽  
Vol 184 (2) ◽  
pp. 296-300 ◽  
Author(s):  
László Kátó ◽  
Béla Gözsy
Keyword(s):  
Fluid Flow ◽  
Tissue Damage ◽  
Inflammatory Process ◽  
Defense Mechanism ◽  
Volatile Oils ◽  
Time Intervals ◽  
Cellular Defense ◽  
Intradermal Administration ◽  
Flow Through

Experiments are presented to the effect that in an inflammatory process histamine and leucotaxin appear successively at different and orderly time intervals, thus assuring an increased fluid flow through the capillary wall. Histamine is released not only in the inflammatory process but also by intradermal administration of such substances (volatile oils or their components) which induce neither the triple response of Th. Lewis nor any tissue damage. This could be explained by the fact that in the tissues histamine is ‘present’ but leucotaxin is ‘formed.’

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

scholarly journals Mechanisms of Colorectal Cancer Prevention by Aspirin—A Literature Review and Perspective on the Role of COX-Dependent and -Independent Pathways

2020 ◽  
Vol 21 (23) ◽  
pp. 9018
Author(s):  
Ranjini Sankaranarayanan ◽  
D. Ramesh Kumar ◽  
Meric A. Altinoz ◽  
G. Jayarama Bhat
Keyword(s):  
Salicylic Acid ◽  
Cancer Prevention ◽  
Protective Actions ◽  
Direct Exposure ◽  
Anti Cancer ◽  
Chemopreventive Effect ◽  
Colorectal Cancer Prevention ◽  
Preclinical And Clinical Studies ◽  
Shed Light

Aspirin, synthesized and marketed in 1897 by Bayer, is one of the most widely used drugs in the world. It has a well-recognized role in decreasing inflammation, pain and fever, and in the prevention of thrombotic cardiovascular diseases. Its anti-inflammatory and cardio-protective actions have been well studied and occur through inhibition of cyclooxygenases (COX). Interestingly, a vast amount of epidemiological, preclinical and clinical studies have revealed aspirin as a promising chemopreventive agent, particularly against colorectal cancers (CRC); however, the primary mechanism by which it decreases the occurrences of CRC has still not been established. Numerous mechanisms have been proposed for aspirin’s chemopreventive properties among which the inhibition of COX enzymes has been widely discussed. Despite the wide attention COX-inhibition has received as the most probable mechanism of cancer prevention by aspirin, it is clear that aspirin targets many other proteins and pathways, suggesting that these extra-COX targets may also be equally important in preventing CRC. In this review, we discuss the COX-dependent and -independent pathways described in literature for aspirin’s anti-cancer effects and highlight the strengths and limitations of the proposed mechanisms. Additionally, we emphasize the potential role of the metabolites of aspirin and salicylic acid (generated in the gut through microbial biotransformation) in contributing to aspirin’s chemopreventive actions. We suggest that the preferential chemopreventive effect of aspirin against CRC may be related to direct exposure of aspirin/salicylic acid or its metabolites to the colorectal tissues. Future investigations should shed light on the role of aspirin, its metabolites and the role of the gut microbiota in cancer prevention against CRC.

scholarly journals Internal melt figures in ice by rapid adiabatic compression

1994 ◽  
Vol 40 (134) ◽  
pp. 132-134
Author(s):  
R.E. Gagnon ◽  
C. Tulk ◽  
H. Kiefte
Keyword(s):  
Phase Transformations ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Adiabatic Compression ◽  
Air Bubbles ◽  
Water Ice ◽  
Deep Focus ◽  
And Behavior ◽  
First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

Spin-Lattice Coupling and Peculiarities of Magnetic Behavior of Ferrimagnetic Ludwigites Mn0.52+M1.52+Mn3+BO5(M=Cu, Ni)

2015 ◽  
Vol 233-234 ◽  
pp. 133-136 ◽  
Author(s):  
Leonard Bezmaternykh ◽  
Evgeniya Moshkina ◽  
Evgeniy Eremin ◽  
Maxim Molokeev ◽  
Nikita Volkov ◽  
...  
Keyword(s):  
Temperature Field ◽  
Low Temperature ◽  
Magnetic Anisotropy ◽  
Single Crystals ◽  
Magnetic Behavior ◽  
Temperature Hysteresis ◽  
Spin Lattice ◽  
Field Magnetization ◽  
Lattice Coupling

Temperature-field and orientational magnetization dependences of single crystals were measured. Both samples demonstrate significant field-depending temperature hysteresis and low-temperature counter field magnetization. The correlation of orientational dependences of these effects and magnetic anisotropy is analyzed; the role of spin-lattice interactions is discussed.

Deep Level Related Yellow Luminescence in P-Type GaN Grown by MBE on (0001) Sapphire

1999 ◽  
Vol 595 ◽  
Author(s):  
Giancarlo Salviati ◽  
Nicola Armani ◽  
Carlo Zanotti-Fregonara ◽  
Enos Gombia ◽  
Martin Albrecht ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Deep Level ◽  
Cubic Phase ◽  
Donor Level ◽  
Yellow Luminescence ◽  
Wurtzite Phase ◽  
Shallow Acceptor ◽  
Deep Donor ◽  
P Type ◽  
Deep Donor Level

AbstractYellow luminescence (YL) has been studied in GaN:Mg doped with Mg concentrations ranging from 1019 to 1021 cm−3 by spectral CL (T=5K) and TEM and explained by suggesting that a different mechanism could be responsible for the YL in p-type GaN with respect to that acting in n-type GaN.Transitions at 2.2, 2.8, 3.27, 3.21, and 3.44 eV were found. In addition to the wurtzite phase, TEM showed a different amount of the cubic phase in the samples. Nano tubes with a density of 3×109 cm−2 were also observed by approaching the layer/substrate interface. Besides this, coherent inclusions were found with a diameter in the nm range and a volume fraction of about 1%.The 2.8 eV transition was correlated to a deep level at 600 meV below the conduction band (CB) due to MgGa-VN complexes. The 3.27 eV emission was ascribed to a shallow acceptor at about 170-190 meV above the valence band (VB) due to MgGa.The 2.2 eV yellow band, not present in low doped samples, increased by increasing the Mg concentration. It was ascribed to a transition between a deep donor level at 0.8-1.1 eV below the CB edge due to NGa and the shallow acceptor due to MgGa. This assumption was checked by studying the role of C in Mg compensation. CL spectra from a sample with high C content showed transitions between a C-related 200 meV shallow donor and a deep donor level at about 0.9- 1.1 eV below the CB due to a NGa-VN complex. In our hypothesis this should induce a decrease of the integrated intensity in both the 2.2 and 2.8 eV bands, as actually shown by CL investigations.

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