Blueshift of bandgap energy and reduction of non-radiative defect density due to precise control of InAs-on-GaSb interface in type-II InAs/GaSb superlattice

2011 ◽  
Vol 110 (12) ◽  
pp. 123103 ◽  
Author(s):  
A. Jasik ◽  
I. Sankowska ◽  
D. Pierścińska ◽  
K. Regiński ◽  
K. Pierściński ◽  
...  
Keyword(s):  
Defect Density ◽  
Bandgap Energy ◽  
Type Ii ◽  
Precise Control ◽  
Radiative Defect

Defect density reduction in InAs/GaSb type II superlattice focal plane array infrared detectors

2011 ◽  
Author(s):  
Martin Walther ◽  
Robert Rehm ◽  
Johannes Schmitz ◽  
Jasmin Niemasz ◽  
Frank Rutz ◽  
...  
Keyword(s):  
Focal Plane ◽  
Infrared Detectors ◽  
Defect Density ◽  
Focal Plane Array ◽  
Type Ii ◽  
Type Ii Superlattice ◽  
Density Reduction

Photoluminescence characterization of non-radiative defect density on silicon surfaces and interfaces at room temperature

2000 ◽  
Vol 364 (1-2) ◽  
pp. 196-199 ◽  
Author(s):  
V.Yu. Timoshenko ◽  
A.B. Petrenko ◽  
Th. Dittrich ◽  
W. Füssel ◽  
J. Rappich
Keyword(s):  
Room Temperature ◽  
Defect Density ◽  
Silicon Surfaces ◽  
Surfaces And Interfaces ◽  
Radiative Defect

PL and FTIR Absorption Study on Porous Silicon in Situ During Etching, in Oxygen Ambient, and After Chemical Oxidation

1992 ◽  
Vol 283 ◽  
Author(s):  
G. Mauckner ◽  
T. Walter ◽  
T. Baier ◽  
K. Thonke ◽  
R. Sauer Abteilung
Keyword(s):  
Defect Density ◽  
Chemical Oxidation ◽  
Laser Exposure ◽  
Porous Si ◽  
Radiative Recombination Rate ◽  
Time Resolved ◽  
Radiative Defect ◽  
Recombination Lifetimes ◽  
Time Resolved Photoluminescence

ABSTRACTSteady state and time-resolved photoluminescence (PL) and Fourier-transform infrared (FTIR) spectroscopy have been performed in situ during etching, on “as prepared” porous Si in air under laser exposure and on chemically oxidized porous Si. We suppose that PLdegradation of “as prepared” porous Si is caused by creating non-radiative defect centers during photooxidation. Chemically oxidized porous Si shows increased PL intensity and longer recombination lifetimes as compared to non-oxidized samples. We conclude, that an oxide layer with low defect density on the inner surface of chemically oxidized porous Si reduces the non-radiative recombination rate.

A Caenorhabditis elegans type I TGF beta receptor can function in the absence of type II kinase to promote larval development

Development ◽  
2000 ◽  
Vol 127 (15) ◽  
pp. 3337-3347 ◽  
Author(s):  
C.V. Gunther ◽  
L.L. Georgi ◽  
D.L. Riddle
Keyword(s):  
Caenorhabditis Elegans ◽  
Fluorescent Protein ◽  
Type I ◽  
Receptor Complex ◽  
Type Ii ◽  
Precise Control ◽  
Dauer Larva ◽  
Protein Receptor ◽  
Morphogenetic Protein ◽  
Green Fluorescent

The daf-4 gene encodes a type II bone morphogenetic protein receptor in Caenorhabditis elegans that regulates dauer larva formation, body size and male tail patterning. The putative type I receptor partner for DAF-4 in regulating dauer larva formation is DAF-1. Genetic tests of the mechanism of activation of these receptors show that DAF-1 can signal in the absence of DAF-4 kinase activity. A daf-1 mutation enhances dauer formation in a daf-4 null background, whereas overexpression of daf-1 partially rescues a daf-4 mutant. DAF-1 alone cannot fully compensate for the loss of DAF-4 activity, indicating that nondauer development normally results from the activities of both receptors. DAF-1 signaling in the absence of a type II kinase is unique in the type I receptor family. The activity may be an evolutionary remnant, owing to daf-1's origin near the type I/type II divergence, or it may be an innovation that evolved in nematodes. daf-1 and daf-4 promoters both mediated expression of green fluorescent protein in the nervous system, indicating that a DAF-1/DAF-4 receptor complex may activate a neuronal signaling pathway. Signaling from a strong DAF-1/DAF-4 receptor complex or a weaker DAF-1 receptor alone may provide larvae with more precise control of the dauer/nondauer decision in a range of environmental conditions.

scholarly journals A Study of Defects in InAs/GaSb Type-II Superlattices Using High-Resolution Reciprocal Space Mapping

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4940
Author(s):  
Iwona Sankowska ◽  
Agata Jasik ◽  
Krzysztof Czuba ◽  
Jacek Ratajczak ◽  
Paweł Kozłowski ◽  
...  
Keyword(s):  
High Resolution ◽  
Diffuse Scattering ◽  
Defect Density ◽  
Stacking Faults ◽  
Diffraction Method ◽  
Reciprocal Space ◽  
Type Ii ◽  
Scattering Intensity ◽  
Type Ii Superlattices ◽  
Diffuse Scattering Intensity

In this paper, he study of defects in InAs/GaSb type-II superlattices using high-resolution an x-ray diffraction method as well as scanning (SEM) and transmission (TEM) electron microscopy is presented. The investigated superlattices had 200 (#SL200), 300 (#SL300), and 400 (#SL400) periods and were grown using molecular beam epitaxy. The growth conditions differed only in growth temperature, which was 370 °C for #SL400 and #SL200, and 390 °C for #SL300. A wings-like diffuse scattering was observed in reciprocal space maps of symmetrical (004) GaSb reflection. The micrometer-sized defect conglomerates comprised of stacking faults, and linear dislocations were revealed by the analysis of diffuse scattering intensity in combination with SEM and TEM imaging. The following defect-related parameters were obtained: (1) integrated diffuse scattering intensity of 0.1480 for #SL400, 0.1208 for #SL300, and 0.0882 for #SL200; (2) defect size: (2.5–3) μm × (2.5–3) μm –#SL400 and #SL200, (3.2–3.4) μm × (3.7–3.9) μm –#SL300; (3) defect diameter: ~1.84 μm –#SL400, ~2.45 μm –#SL300 and ~2.01 μm –#SL200; (4) defect density: 1.42 × 106 cm−2 –#SL400, 1.01 × 106 cm−2 –#SL300, 0.51 × 106 cm−2 –#SL200; (5) diameter of stacking faults: 0.14 μm and 0.13 μm for #SL400 and #SL200, 0.30 μm for #SL300.

scholarly journals First-Principles Analysis of Vibrational Properties of Type II SiGe Alloy Clathrates

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 723
Author(s):  
Dong Xue ◽  
Charles W. Myles
Keyword(s):  
First Principles ◽  
Silicon Germanium ◽  
Density Functional ◽  
Negative Thermal Expansion ◽  
Bandgap Energy ◽  
Energy Calculation ◽  
Type Ii ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Transverse Acoustic

We have mostly performed vibrational studies of Type-II silicon-germanium clathrate alloys, namely, Si136-xGex (0 < x ≤ 128), using periodic density functional theory (DFT). Our computed lattice constant for various stoichiometric amount, namely, x, of Ge agrees to some extent with the observed X-ray diffraction (XRD) data, along with monotonically increasing dependence on x. According to our bandgap energy calculation via Vienna ab initio simulation package (VASP), Si128Ge8 has a “nearly-direct” bandgap of approximately 1.27 eV, which agrees well with the previously calculated result (~1.23 eV), which was obtained using the Cambridge sequential simulation total energy package (CASTEP). Most of our first-principles calculations focus on exploring the low-energy transverse acoustic (TA) phonons that contribute dominantly to the induction of negative thermal expansion (NTE) behavior. Moreover, our work has predicted that the Si104Ge32 framework exhibits NTE in the temperature range of 3–80 K, compared to the temperature regime (10–140 K) of NTE observed in such pure Si136. It is posited that the increased number of Ge–Ge bonds may weaken the NTE effect substantially, as the composition, which is denoted as x, in Si136-xGex is elevated from 32 (or 40) to 96 (or 104).

Type II Solar Radio Bursts over Solar Cycle 21

1994 ◽  
Vol 144 ◽  
pp. 283-284
Author(s):  
G. Maris ◽  
E. Tifrea
Keyword(s):  
Solar Radio ◽  
Interplanetary Space ◽  
Impulsive Phase ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Strong Energy ◽  
Mass Ejection ◽  
Geophysical Effect ◽  
Radio Event

The type II solar radio bursts produced by a shock wave passing through the solar corona are one of the most frequently studied solar activity phenomena. The scientific interest in this type of phenomenon is due to the fact that the presence of this radio event in a solar flare is an almost certain indicator of a future geophysical effect. The origin of the shock waves which produce these bursts is not at all simple; besides the shocks which are generated as a result of a strong energy release during the impulsive phase of a flare, there are also the shocks generated by a coronal mass ejection or the shocks which appear in the interplanetary space due to the supplementary acceleration of the solar particles.

Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device

1970 ◽  
Vol 28 ◽  
pp. 106-107 ◽  
Author(s):  
Ronald S. Weinstein ◽  
N. Scott McNutt
Keyword(s):  
New Zealand ◽  
General Hospital ◽  
Massachusetts General Hospital ◽  
Type I ◽  
Type Ii ◽  
Collaborative Effort ◽  
Temperature And Pressure ◽  
The University

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.

Ultrastructure of pulmonary microvasculature in acute endotoxemia

1978 ◽  
Vol 36 (2) ◽  
pp. 470-471
Author(s):  
R. G. Gerrity ◽  
M. Richardson
Keyword(s):  
Polymorphonuclear Leukocytes ◽  
Alveolar Epithelium ◽  
Endothelial Damage ◽  
Capillary Endothelium ◽  
Type Ii Cells ◽  
Type Ii ◽  
Interstitial Edema ◽  
Pulmonary Capillaries ◽  
Lung Ultrastructure ◽  
Fibrin Thrombi

Dogs were injected intravenously with E_. coli endotoxin (2 mg/kg), and lung samples were taken at 15 min., 1 hr. and 24 hrs. At 15 min., occlusion of pulmonary capillaries by degranulating platelets and polymorphonuclear leukocytes (PML) was evident (Fig. 1). Capillary endothelium was intact but endothelial damage in small arteries and arterioles, accompanied by intraalveolar hemorrhage, was frequent (Fig. 2). Sloughing of the surfactant layer from alveolar epithelium was evident (Fig. 1). At 1 hr., platelet-PML plugs were no longer seen in capillaries, the endothelium of which was often vacuolated (Fig. 3). Interstitial edema and destruction of alveolar epithelium were seen, and type II cells had discharged their granules into the alveoli (Fig. 4). At 24 hr. phagocytic PML's were frequent in peripheral alveoli, while centrally, alveoli and vessels were packed with fibrin thrombi and PML's (Fig. 5). In similar dogs rendered thrombocytopenic with anti-platelet serum, lung ultrastructure was similar to that of controls, although PML's were more frequently seen in capillaries in the former (Fig. 6).

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

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