The Nature of Point Defects and their Influence on Diffusion Processes in Silicon at High Temperatures

1982 ◽  
Vol 14 ◽  
Author(s):  
U. GÖsele ◽  
T.Y. Tan
Keyword(s):  
Diffusion Processes ◽  
Surface Oxidation ◽  
Group V ◽  
Group Iii ◽  
Self Diffusion ◽  
Slowing Down ◽  
Silicon Crystals ◽  
Order Of Magnitude ◽  
Theoretical Results

ABSTRACTThe paper highlights recent progress in understanding the role of vacancies and self-interstitials in self- and impurity diffusion in silicon above about 700°C. How surface oxidation of silicon leads to a perturbation of the pointdefect population is described. An analysis of the resulting oxidationenhanced or -retarded diffusion of group III and group V dopants shows that under thermal equilibrium as well as under oxidation conditions both vacancies and self-interstitials are present. For sufficiently long times vacancies and self-interstitials attain dynamical equilibrium which involves their recombination and spontaneous thermal creation in the bulk of silicon crystals. The existence and the nature of a recombination barrier slowing down the recombination process are discussed in this context. Recent experimental and theoretical results on the diffusion of gold in silicon enable us to determine the selfinterstitial component of silicon self-diffusion and to obtain an estimate of the respective vacancy contribution. The two components turn out to be of the same order of magnitude from 700°C up to the melting point.

Intrinsic Point Defects and Diffusion Processes in Silicon

1983 ◽  
Vol 31 ◽  
Author(s):  
T. Y. Tan
Keyword(s):  
Point Defects ◽  
Thermal Equilibrium ◽  
Diffusion Processes ◽  
Equilibrium Concentration ◽  
Surface Oxidation ◽  
Self Diffusion ◽  
Equilibrium Concentrations ◽  
And Diffusion

ABSTRACTThis paper reviews recent progress in understanding the role of vacancies (V) and self-interstitials (I) in self and impurity diffusion in Si. Surface oxidation perturbs the thermal equilibrium concentration of point defects and analyses of the resulting effects on dopant diffusion showed that both V and I are present. Developments in experimental and theoretical works on Au diffusion in Si yielded a determination of the I-component and an estimate of the V-component of the Si self-diffusion coefficient. It is hoped that the I and V thermal equilibrium concentrations may be determined in the near future.A number of important physical aspects of the anomalous diffusion of P are now understood but a basically satisfactory model may need further work.

Diffusion Mechanisms in Sige Alloys

1999 ◽  
Vol 568 ◽  
Author(s):  
Arthur F.W. Willoughby ◽  
Janet M. Bonar ◽  
Andrew D.N. Paine
Keyword(s):  
Diffusion Processes ◽  
Dopant Diffusion ◽  
Elemental Silicon ◽  
Self Diffusion ◽  
Si Substrates ◽  
Marker Layer ◽  
Diffusion Mechanisms ◽  
Silicon And Germanium ◽  
Charged Defects

ABSTRACTInterest in diffusion processes in SiGe alloys arises from their potential in HBT's, HFET's, and optoelectronics devices, where migration over distances as small as a few nanometres can be significant. Successful modelling of these processes requires a much improved understanding of the mechanisms of self- and dopant diffusion in the alloy, although recent progress has been made. It is the purpose of this review to set this in the context of diffusion processes in elemental silicon and germanium, and to identify how this can help to elucidate behaviour in the alloy. Firstly, self diffusion processes are reviewed, from general agreement that self-diffusion in germanium is dominated by neutral and acceptor vacancies, to the position in silicon which is still uncertain. Germanium diffusion in silicon, however, appears to be via both vacancy and interstitial processes, and in the bulk alloy there is evidence for a change in dominant mechanism at around 35 percent germanium. Next, a review of dopant diffusion begins with Sb, which appears to diffuse in germanium by a mechanism similar to self-diffusion, and in silicon via monovacancies also, from marker layer evidence. In SiGe, the effects of composition and strain in epitaxial layers on Si substrates are also consistent with diffusion via vacancies, but questions still remain on the role of charged defects. The use of Sb to monitor vacancy effects such as grown-in defects by low temperature MBE, are discussed. Lastly, progress in assessing the role of vacancies and interstitials in the diffusion of boron is reviewed, which is dominated by interstitials in silicon-rich alloys, but appears to change to domination by vacancies at around 40 percent germanium, although studies in pure germanium are greatly needed.

MOCVD Growth of InAlAsSb Layer for High-Breakdown Voltage HEMT Applications

2003 ◽  
Vol 799 ◽  
Author(s):  
Haruki Yokoyama ◽  
Hiroki Sugiyama ◽  
Yasuhiro Oda ◽  
Michio Sato ◽  
Noriyuki Watanabe ◽  
...  
Keyword(s):  
Schottky Barrier ◽  
Chemical Vapor ◽  
Composition Analysis ◽  
Group V ◽  
Group Iii ◽  
Mocvd Growth ◽  
Order Of Magnitude ◽  
Etch Stop ◽  
Etch Stop Layer ◽  
Inp Substrates

ABSTRACTThis paper studies the decomposition characteristic of group-III sources during InAlAsSb growth on InP substrates by metalorganic chemical vapor deposition (MOCVD) using trimethylindium (TMI), trimethylaluminum (TMA), trimethylantimony (TMSb) and arsine (AsH3). A composition analysis of InAlAsSb layers shows that the group-III compositions in the InAlAsSb layer change remarkably when the flow rate of the group-V source is varied. To clarify the reason for this phenomenon, the growth rates of InAsSb and AlAsSb component are examined. Their changes indicate that TMSb suppresses the decomposition of TMA while AsH3 enhances it. Moreover, the HEMT structure with InP/InAlAsSb Schottky barrier layer, whose InP layer acts as a recess-etch-stop layer, is fabricated for the first time. The I-V characteristics of a fabricated Schottky barrier diode indicate that the reverse leakage current of InP/InAlAsSb is about one order of magnitude smaller than that of commonly used InP/InAlAs.

From the Mystery to the Understanding of the Self-Interstitials in Silicon

1980 ◽  
Vol 2 ◽  
Author(s):  
W. Frank ◽  
A. Seeger ◽  
U. Gösele
Keyword(s):  
High Temperature ◽  
The Self ◽  
Experimental Conditions ◽  
Group V ◽  
Group Iii ◽  
Enhanced Diffusion ◽  
Self Diffusion ◽  
Thermally Activated ◽  
Temperature Equilibrium ◽  
K Concentration

ABSTRACTOur present knowledge on self-interstitials in silicon and the rôle these defects play under widely different experimental conditions are surveyed. In particular, the following phenomena involving self-interstitials either in supersaturations or under high-temperature thermal-equilibrium conditions are considered: mobility-enhanced diffusion of self-interstitials below liquid-helium temperature, thermally activated diffusion of self-interstitials at inter-mediate temperatures (14O K to 600 K), concentration-enhanced diffusion of Group-III or Group-V elements in silicon at higher temperatures, and— as examples for high-temperature equilibrium phenomena — self-diffusion and diffusion of gold in silicon. This leads to the picture that the self-interstitials in silicon may occur in different electrical charge states and possess dumbbell configurations or are extended over several atomic volumes at intermediate or high temperatures, respectively.

scholarly journals EVALUATION OF THE PROPHYLACTIC ROLE OF INDIAN SHRIMP IN ALUMINUM CHLORIDE-INDUCED ALZHEIMER’S DISEASE ON EXPERIMENTAL RATS

2019 ◽  
pp. 377-382
Author(s):  
RAMACHANDRAN S ◽  
SRI RAMYA M ◽  
LIZA U ◽  
LAKSHMI PRASANNA PS ◽  
SARISHMA K
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Aluminum Chloride ◽  
Group Iv ◽  
Group V ◽  
Group Iii ◽  
Group I ◽  
Male Wistar Rats ◽  
The Brain

Objective: This work was aimed to investigate the prophylactic and therapeutic role of Indian shrimp in aluminum chloride-induced Alzheimer’s disease (AD) in rats. Methods: The male Wistar rats were selected and divided into six groups. Group I received distilled water, Group II received AlCl3 ( 100 mg/kg, p.o.), Group III received rivastigmine (1 mg/kg, p.o.), Group IV received AlCl3 + shrimp powder (200 mg/kg, p.o), and Group V received AlCl3 + shrimp powder (400 mg/kg, p.o) for 60 days. At the end of the study, various parameters such as behavioral and biochemical investigations were assessed. Results: The result of the study shows that the shrimp (400 mg/kg) has better effect on the treatment of aluminum chloride-induced AD in rats. It showed a remarkable improvement in the behavioral and biochemical parameters, and the result of histopathology study shows that the hippocampus region of brain tissue recovered as compared with control. Conclusion: From this study, it is evident that dietary intake of shrimp can help to inhibit oxidative stress produced due to the accumulation of AlCl3 in the brain and used as a prophylactic for AD.

Indomethacin blunts ethchlorvynol-induced pulmonary hypertension but not pulmonary edema

1982 ◽  
Vol 53 (3) ◽  
pp. 563-566 ◽  
Author(s):  
F. L. Glauser ◽  
R. P. Fairman ◽  
J. E. Millen ◽  
R. K. Falls
Keyword(s):  
Pulmonary Hypertension ◽  
Placebo Group ◽  
Pulmonary Edema ◽  
Group Iv ◽  
Group V ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
Permeability Pulmonary Edema

Ethchlorvynol (10 mg/kg) causes transient pulmonary hypertension and an increased permeability pulmonary edema in sheep. To determine the role of cyclooxygenase and its metabolites, histamine, and catecholamines in both phenomena, we studied five groups of sheep: group I, placebo; group II, ethchlorvynol; group III, indomethacin with ethchlorvynol; group IV, diphenhydramine with ethchlorvynol; group V, phentolamine with ethchlorvynol. Indomethacin, but not diphenhydramine or phentolamine, blunted the pulmonary hypertensive response seen immediately following the ethchlorvynol injection. However, none of the drugs had any effect on the increased permeability pulmonary edema. We conclude that cyclooxygenase or its metabolites partially mediates the hypertensive response but not the increased permeability pulmonary edema seen in sheep following ethchlorvynol injection.

Transport in the Critical Region

2005 ◽  
Author(s):  
Eldred H. Chimowitz
Keyword(s):  
Random Walk ◽  
Critical Region ◽  
Diffusion Processes ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Two Dimensions ◽  
Thermally Induced ◽  
Self Diffusion ◽  
Slowing Down ◽  
Definition Of

The behavior of dynamic properties in the critical region is important in many engineering applications, and in this chapter we investigate this topic, focusing upon diffusion. In the literature, the term critical slowing down is used to describe the long relaxation times that occur when criticality is approached. Does this mean that diffusion processes per se come to a halt and, if not, how does slowing down manifest itself in fluids? We see that, in spite of the nonequilibrium nature of this topic, equilibrium concepts still play a key role in describing dynamics in the critical region. To begin this discussion, we investigate the dynamic behavior of a tagged fluid molecule as it experiences random fluctuations in its position in the fluid. These fluctuations would be induced by random thermally induced collisions between the tagged species and other fluid molecules. This type of dynamics is referred to as Brownian motion or a random walk. A schematic showing two 10-step trajectories depicting a random walk in two dimensions is shown in figure 12.1, and its analysis leads naturally to the definition of the self-diffusion coefficient.

The Quantitative Ultrastructure of the Heart Muscle of Japanese Quail by Hypergravitation, Hypodynamy and Combination

1990 ◽  
Vol 48 (3) ◽  
pp. 188-189
Author(s):  
Anton Bózner ◽  
Mikuláš Gažo ◽  
Jozef Dostál
Keyword(s):  
Japanese Quail ◽  
Heart Muscle ◽  
Relative Size ◽  
Combination Group ◽  
Control Group ◽  
Group V ◽  
Group Iii ◽  
Space Flights ◽  
Group I ◽  
Quantitative Ultrastructure

It is anticipated that Japanese quail /Coturnix coturnix japonica/ will provide animal proteins in long term space flights. Consequently this species of birds is of research interest of international space program INTERCOSMOS. In the year 1987 we reported on an experiment /2/ in which the effect of chronic acceleration of 2 G hypergravitation, the hypodynamy and the simultaneous effect of chronic acceleration and the location in the centre of the turntable of the centrifuge on the protein fractions in skeletal muscles was studied. The ultrastructure of the heart muscle was now in this experiments examined as well.Japanese quail cockerels, aged 48 days were exposed to 2 G hypergravitation /group IV/ in a 6,4 m diameter centrifuge, to hypodynamy /group III/ and their combination /group V/, respectively for 6 days / Fig.1/. The hypodynamy in group III was achieved by suspending the birds in jackets without contact the floor. The group II was located in the centre ofthe turntable of the centrifuge. The control group I. was kept under normal conditions. The quantitative ultrastructure of myocard was evaluated by the methods of Weibel/3/ - this enables to determine the number, relative size and volume of mitochondria volume of single mitochondria, defficiency of mitochondrial cristae and volume of myofibrils.

Clustering-Triggered Efficient Room Temperature Phosphorescence from Nonconventional Luminophores

2019 ◽  
Author(s):  
Shuyuan Zheng ◽  
Taiping Hu ◽  
Xin Bin ◽  
Yunzhong Wang ◽  
Yuanping Yi ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Efficiency ◽  
Spin Orbit Coupling ◽  
Design Rationale ◽  
Emission Mechanism ◽  
Room Temperature Phosphorescence ◽  
Electronic Interactions ◽  
Energy Gaps ◽  
Theoretical Results

Pure organic room temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Here we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boost the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5% is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results would spur the future fabrication of nonconventional phosphors, and moreover should advance understanding of the underlying emission mechanism.<br>

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