Luminescence from individual dislocations in II-VI and III-V semiconductors

1991 ◽  
Vol 49 ◽  
pp. 834-835
Author(s):  
J W Steeds
Keyword(s):  
Group Iv ◽  
Luminescence Properties ◽  
Carrier Recombination ◽  
Transmission Electron ◽  
Wide Range ◽  
Basic Physics ◽  
Semiconducting Compounds ◽  
Diamond Group ◽  
Non Destructive ◽  
Technological Significance

There is a wide range of experimental results related to dislocations in diamond, group IV, II-VI, III-V semiconducting compounds, but few of these come from isolated, well-characterized individual dislocations. We are here concerned with only those results obtained in a transmission electron microscope so that the dislocations responsible were individually imaged. The luminescence properties of the dislocations were studied by cathodoluminescence performed at low temperatures (~30K) achieved by liquid helium cooling. Both spectra and monochromatic cathodoluminescence images have been obtained, in some cases as a function of temperature.There are two aspects of this work. One is mainly of technological significance. By understanding the luminescence properties of dislocations in epitaxial structures, future non-destructive evaluation will be enhanced. The second aim is to arrive at a good detailed understanding of the basic physics associated with carrier recombination near dislocations as revealed by local luminescence properties.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

Structural and electronic properties of defects in semiconductors

1995 ◽  
Vol 53 ◽  
pp. 4-5
Author(s):  
J.L. Batstone
Keyword(s):  
Semiconductor Device ◽  
Chemical Vapor ◽  
Misfit Strain ◽  
Organic Chemical ◽  
Extended Defects ◽  
Transmission Electron ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Metal Organic ◽  
Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

Effects of Atovaquone on the Ultrastructural Morphology of Pneumocystis Carinii

1997 ◽  
Vol 3 (S2) ◽  
pp. 81-82
Author(s):  
M.P. Goheen ◽  
M.S. Bartlett ◽  
M.M. Shaw ◽  
S.R. Meshnick ◽  
J.W. Smith
Keyword(s):  
Adverse Reactions ◽  
Pneumocystis Carinii ◽  
Spinner Flask ◽  
Short Term ◽  
Human Embryonic Lung ◽  
Transmission Electron ◽  
Significant Incidence ◽  
Wide Range ◽  
Acquired Immunodeficiency ◽  
Immunodeficiency Syndrome

Pneumocystis carinii pneumonia (PCP) occurs at some time in most patients with acquired immunodeficiency syndrome (AIDS). Trimethoprim/sulfamethoxazole or pentamidine isothionate are the traditional modes of therapy for treatment and prophylaxis of PCP. Unfortunately these drugs are associated with a significant incidence of adverse side effects particularly in patients with AIDS. Toxicity and a growing concern that P. carinii strains are becoming resistant to these compounds is providing the impetus for the search for additional drugs to combat P. carinii. Atovaquone, developed as an antimalarial agent, has activity against a wide range of other organisms, including Toxoplasma sp. and P. carinii, with a lower incidence of adverse reactions during clinical trials. Atovaquone inhibits mitochondrial respiration in P. falciparum and P. carinii. In this study transmission electron microscopy (TEM) was used to observe the effects of atovaquone on P. carinii organisms in short term spinner flask culture.Spinner flask cultures of human embryonic lung cells were inoculated with P. carinii from infected rat lung.

IR and MW Absorption Techniques for Bulk and Surface Recombination Control in High-Quaiity Silicon

1995 ◽  
Vol 386 ◽  
Author(s):  
A. Kaniava ◽  
U. Menczigar ◽  
J. Vanhellemont ◽  
J. Poortmans ◽  
A. L. P. Rotondaro ◽  
...  
Keyword(s):  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Silicon Substrates ◽  
Injection Level ◽  
Effective Lifetime ◽  
Carrier Recombination ◽  
High Injection Level ◽  
High Injection ◽  
Wide Range ◽  
Recombination Velocity

ABSTRACTThe carrier recombination rate in high-quality FZ and Cz silicon substrates is studied by contactless infrared and microwave absorption techniques. Different surface treatments covering a wide range of surface recombination velocity have been used for the separation of bulk and surface recombination components and evaluating of the efficiency of passivation. Limitations of effective lifetime approach are analyzed specific for low and high injection level. Sensitivity limits of the techniques for iron contamination are discussed

scholarly journals Microcharacterization of Interfaces

1982 ◽  
Vol 18 ◽  
Author(s):  
P. M. PETROFF
Keyword(s):  
Phase Contrast ◽  
Molecular Beam ◽  
Minority Carrier ◽  
Carrier Recombination ◽  
Roughening Transition ◽  
Semiconductor Heterostructure ◽  
Transmission Electron ◽  
Quantum Well Wire ◽  
Interfacial Strain

The atomic structure of semiconductor heterostructure interfaces and metalsemiconductor interfaces are best characterized by transmission electron microscopy (TEM). Both phase contrast TEM and structure factor contrast TEM are able to distinguish very small structural (two monolayers) or compositional (less than 0.2%) fluctuations at interfaces. Applications of these techniques to the study of the roughening transition temperature at the Gal−xAlxAs–GaAs and Ga1−xAlxAs–Ge interfaces grown by molecular beam epitaxy are presented. Minority carrier recombination at interfaces is characterized on a microscopic scale by low temperature cathodoluminescence. This technique is used to demonstrate the role of interfaces in gettering defects in Gal1−xAlxAs/GaAs heterostructures. Finally, the effects of interfacial strain in producing a localization of the luminescence in GaAs quantum well wire structures will be discussed.

Interfaces in Structural Ceramics

MRS Bulletin ◽  
1990 ◽  
Vol 15 (10) ◽  
pp. 51-59 ◽  
Author(s):  
M. Grant Norton ◽  
C. Barry Carter
Keyword(s):  
Structural Ceramics ◽  
Interface Engineering ◽  
Micro Structure ◽  
Complete Understanding ◽  
Intimate Contact ◽  
Transmission Electron ◽  
Processed Material ◽  
Wide Range ◽  
Alternative Materials ◽  
The Relationship

Structural ceramics are necessarily polycrystalline and their usefulness is largely determined by the interfaces between the grains. The relationship between the structure and chemistry of different interfaces and the micro-structure can be illustrated by reviewing studies of interfaces in a wide range of materials including such classical ceramics as Al2O3, the current “hightech” polyphase ceramics exemplified by ZrO2-toughened Al2O3, and the composite materials of the future. Using transmission electron microscopy is essential for a complete understanding, but limitations to its use must be recognized. Only by understanding the factors that control the behavior of these interfaces will it become possible to further extend the application of interface engineering.Structural ceramics are a group of materials that can be used for applications requiring their strength to persist at high temperatures or in conditions that would be particularly corrosive to alternative materials, which are usually metallic. Strength and strength-related properties such as toughness depend largely on the microstructural features of the processed material.The microstructure is defined by the morphology and size of the grains and the interfaces between these grains. If the grains are in intimate contact, then the interface is a grain boundary of the type familiar from studies of metals.

Control of properties and structure of steel vessels by cooling in various media at the outlet of rolling and pressing lines

2021 ◽  
pp. 34-38
Author(s):  
R. L. Shatalov ◽  
V. A. Medvedev
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Metal Structure ◽  
Machine Building ◽  
Regression Equations ◽  
Wide Range ◽  
Industrial Mineral ◽  
Cooling Media ◽  
Technological Limitations ◽  
Non Destructive

When controlling the mechanical properties and structure of vessels made of carbon structural steels manufactured by hot deformation on rolling and pressing lines (PPL) of machine-building enterprises of Russia, such cooling media as water, I20 industrial mineral oil, air are used. The applied cooling media are able to provide the workpieces with a given structure with a wide range of mechanical properties. However, the cooling media have a number of technological limitations and conditions of the use, non-compliance with which leads to reject. When cooled in oil, the probability of ignition is high; when cooled in water, hardening cracks may form, and air is not always able to provide the required rate and uniformity of heat transfer to the environment. The efficiency of control of physical and mechanical properties and structure of deformed vessels made of 50 steel by cooling in TERMAT polymer aqueous solutions in different concentrations on PPL of the plant of JSC NPO Pribor was studied. The effect of varying the concentration from 2 to 9% of TERMAT polymer on the formation of metal structure, as well as physical and mechanical properties of hot-deformed vessels was studied. The results of testing the strength and plastic characteristics of vessels by destructive and non-destructive control methods are presented. According to the results of physical and mechanical properties, regression equations were obtained with at least 95% reliability of R2, which establish the relationship between the controlled plastic and strength parameters of the vessel metal`s properties. The conducted researches allowed to compare the indicators of the main physical and mechanical properties of steel vessels at the PPL outlet and to propose methods of inhomogeneity control that reduce time and material costs by 5–10% during the tests.

scholarly journals Autophagy is activated in the ovarian tissue of polycystic ovary syndrome

Reproduction ◽  
2018 ◽  
Vol 155 (1) ◽  
pp. 85-92 ◽  
Author(s):  
Da Li ◽  
Yue You ◽  
Fang-Fang Bi ◽  
Tie-Ning Zhang ◽  
Jiao Jiao ◽  
...  
Keyword(s):  
Polycystic Ovary Syndrome ◽  
Potential Role ◽  
Polycystic Ovary ◽  
Ovarian Tissue ◽  
Ovary Syndrome ◽  
Cellular Processes ◽  
Transmission Electron ◽  
Wide Range ◽  
Response To Stress

The importance of autophagy in polycystic ovary syndrome (PCOS)-related metabolic disorders is increasingly being recognized, but few studies have investigated the role of autophagy in PCOS. Here, transmission electron microscopy demonstrated that autophagy was enhanced in the ovarian tissue from both humans and rats with PCOS. Consistent with this, ovarian granulosa cells from PCOS rats showed increases in the autophagy marker protein light chain 3B (LC3B), whereas levels of the autophagy substrate SQSTM1/p62 were decreased. In addition, the ratio of LC3-II/LC3-I was markedly elevated in human PCOS ovarian tissue compared with normal ovarian tissue. Real-time PCR arrays indicated that 7 and 34 autophagy-related genes were down- and up-regulated in human PCOS , Signal-Net, and regression analysis suggested that there are a wide range of interactions among these 41 genes, and a potential network based on EGFR, ERBB2, FOXO1, MAPK1, NFKB1, IGF1, TP53 and MAPK9 may be responsible for autophagy activation in PCOS. Systematic functional analysis of 41 differential autophagy-related genes indicated that these genes are highly involved in specific cellular processes such as response to stress and stimulus, and are linked to four significant pathways, including the insulin, ERBB, mTOR signaling pathways and protein processing in the endoplasmic reticulum. This study provides evidence for a potential role of autophagy disorders in PCOS in which autophagy may be an important molecular event in the pathogenesis of PCOS.

scholarly journals A framework for corrosion assessment in metallic structures, from data analysis to risk based inspection

2021 ◽  
Vol 23 (1) ◽  
pp. 11-20
Author(s):  
Xiaofei Cui ◽  
Xiaoxia Liang ◽  
Ujjwal Bharadwaj
Keyword(s):  
Corrosion Damage ◽  
Quantitative Information ◽  
Assessment Process ◽  
Steel Bridge ◽  
Destructive Testing ◽  
Metallic Structures ◽  
Wide Range ◽  
Corrosion Assessment ◽  
Metallic Corrosion ◽  
Non Destructive

Metallic corrosion is a big challenge affecting many sectors in a nation’s economy. Necessary corrosion prevention actions have to be taken in order to maintain the integrity of engineering assets susceptible to corrosion. This paper proposes a holistic framework to support the management of corrosion in metallic structures. It is a fully automation corrosion assessment process, with risk updated by Bayesian theory. Through analyzing the thickness data measured by non-destructive testing (NDT) techniques, the influence of corrosion on the component can be estimated using statistical methods, which will enable users to make decisions on maintenance based on quantitative information. A case study using corrosion data from a steel bridge is included to demonstrate the proposed framework. It improved the conventional corrosion analysis method by the proposed statistical approach using representative thickness data, which aims to take full use of the remaining life. This model can be adapted to a wide range of metallic structure suffering from corrosion damage.

scholarly journals FEI Titan 80-300 TEM

2016 ◽  
Vol 2 ◽  
Author(s):  
Andreas Thust ◽  
Juri Barthel ◽  
Karsten Tillmann
Keyword(s):  
Electron Microscope ◽  
Solid State ◽  
Spherical Aberration ◽  
Atomic Scale ◽  
Atomic Resolution ◽  
Lens System ◽  
Stage Design ◽  
Precise Positioning ◽  
Transmission Electron ◽  
Wide Range

The FEI Titan 80-300 TEM is a high-resolution transmission electron microscope equipped with a field emission gun and a corrector for the spherical aberration (<em>C</em><sub>S</sub>) of the imaging lens system. The instrument is designed for the investigation of a wide range of solid state phenomena taking place on the atomic scale, which requires true atomic resolution capabilities. Under optimum optical settings of the image <em>C</em><sub>S</sub>-corrector (CEOS CETCOR) the point-resolution is extended up to the information limit of well below 100 pm with 200 keV and 300 keV electrons. A special piezo-stage design allows ultra-precise positioning of the specimen in all 3 dimensions. Digital images are acquired with a Gatan 2k x 2k slow-scan charged coupled device camera.

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