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.

scholarly journals Influence of TOPO and TOPO-CdSe/ZnS Quantum Dots on Luminescence Photodynamics of InP/InAsP/InPHeterostructure Nanowires

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 640
Author(s):  
Artem I. Khrebtov ◽  
Vladimir V. Danilov ◽  
Anastasia S. Kulagina ◽  
Rodion R. Reznik ◽  
Ivan D. Skurlov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Excited States ◽  
Molecular Beam ◽  
Surface Passivation ◽  
Low Energy ◽  
Trioctylphosphine Oxide ◽  
Reverse Transfer ◽  
Semiconductor Heterostructure ◽  
Ligand Type

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the “reverse transfer” mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.

The Role of Hydrogen in Silicon Microcrystallization

1989 ◽  
Vol 164 ◽  
Author(s):  
S. Wagner ◽  
S.H. Wolff ◽  
J.M. Gibson
Keyword(s):  
Electron Microscope ◽  
Molecular Beam Epitaxy ◽  
Grain Boundary ◽  
Molecular Beam ◽  
Boundary Energy ◽  
Substantial Reduction ◽  
Grain Boundary Energy ◽  
Transmission Electron ◽  
Crystallization Experiments

AbstractWe report and interpret two groups of experiments on the role that hydrogen plays in the formation of silicon microcrystals. We show that the growth of singlecrystal Si by molecular beam epitaxy at 475°C is disrupted by H2, which induces the formation of microcrystals. In crystallization experiments of non-hydrogenated a-Si and of hydrogenated a-Si:H on a hot stage in a transmission electron microscope, hydrogen facilitates the nucleation of crystallites. We explain our observations with a substantial reduction of the grain boundary energy by hydrogen.

The Role of Segregation in InGaAs Heteroepitaxy

2007 ◽  
Vol 539-543 ◽  
pp. 3540-3545 ◽  
Author(s):  
D. Litvinov ◽  
D. Gerthsen ◽  
A. Rosenauer ◽  
M. Schowalter ◽  
Thorsten Passow ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam ◽  
Quantitative Agreement ◽  
Fringe Analysis ◽  
Island Formation ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Photoluminescence Peak ◽  
Floating Layer

We investigated InGaAs layers grown by molecular-beam epitaxy on GaAs (001) with transmission electron microscopy (TEM) and photoluminescence spectroscopy. InGaAs layers with In-concentrations of 16, 25 and 28 % and respective thicknesses of 20, 22 and 23 monolayers were deposited at 535 °C. Island formation is observed for the layer with the highest In-concentration. Inconcentration profiles were obtained from high-resolution TEM images by composition evaluation by lattice fringe analysis. The measured profiles can well be fitted applying the segregation model of Muraki et al. [Appl. Phys. Lett. 61 (1992) 557] and are in excellent quantitative agreement with the photoluminescence peak positions. From our data we conclude that island formation occurs when the amount of Indium in the In-floating layer reaches 1.1±0.2 monolayers indium.

Nature and Formation of Non-Radiative Defects in GaNAs And InGaAsN

2001 ◽  
Vol 692 ◽  
Author(s):  
W. M. Chen ◽  
N. Q. Thinh ◽  
I. A. Buyanova ◽  
P. N. Hai ◽  
H. P. Xin ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Radiative Recombination ◽  
Molecular Beam ◽  
Deep Level ◽  
The Other ◽  
Temperature Growth ◽  
Carrier Recombination ◽  
Recombination Centers ◽  
Optically Detected

AbstractThe optically detected magnetic resonance (ODMR) technique has been employed to examine the nature and formation mechanism of non-radiative defects in GaNAs and InGaAsN. In both alloys, two defects were observed and were shown to be deep-level, non-radiative recombination centers. One of the defects has been identified as a complex involving an AsGa antisite. These two defects gain more importance with increasing N composition up to 3%, presumably due to an increase in their concentration. With a further higher N composition, the defects start to lose importance in carrier recombination that is attributed to an increasingly important role of other new non-radiative channels introduced with a high N composition. On the other hand, effect of In composition up to 3% seems to be only marginal. Both defects were shown to be preferably introduced in the alloys during low-temperature growth by molecular beam epitaxy (MBE), but can be rather efficiently removed by post-growth rapid thermal annealing.

Chemical Origin of the Grain Boundary Carrier Recombination in Silicon Bicrystals

1985 ◽  
Vol 59 ◽  
Author(s):  
F. Battistella ◽  
A. Rocher ◽  
A. George
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Direct Relationship ◽  
Minority Carrier ◽  
Neutral Atmosphere ◽  
X Ray ◽  
Heterogeneous Recombination ◽  
Carrier Recombination ◽  
Transmission Electron

ABSTRACTThe minority carrier recombination related to grain boundaries is studied by the SEM/EBIC technique. The specimens investigated are silicon bicrystals obtained by the Czochralski pulling process. The specimens are heated for 2 hours at 750°C in a neutral atmosphere. Heterogeneous recombination of the grain boundaries is then observed.X-Ray topography and Transmission Electron Microscopy (TEM) have been performed to determine the origin of the heterogeneous recombination. A direct relationship between the local recombination along the grain boundary and the precipitates localized at the interface has been established. The chemical origin of the precipitates is discussed.

Effects of Defects in GaAs/AlGaAs Quantum Wells

1993 ◽  
Vol 325 ◽  
Author(s):  
O.L. Russo ◽  
V. Rehn ◽  
T.W. Nee ◽  
K.A. Dumas
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Wells ◽  
Point Defects ◽  
Molecular Beam ◽  
Transition Probability ◽  
Band Energy ◽  
Transmission Electron ◽  
Different Temperatures

AbstractHigh Resolution transmission electron microscopy (HRTEM) and electroreflectance (ER) were used to explain the role of point defects in the molecular beam epitaxy (MBE) grown PIN structure containing five coupled (50Å/28Å) GaAs/AlxGa1−xAs quantum wells with x = 0.25. The ER data were taken at 300K and 77K for energies from 1.4 to 2.1 eV from which sub-band energy transitions were determined. Data at 300K showed three transitions whereas four were readily resolved at 77K. HRTEM data determined the uniformity of both the wells and barriers to be within ± 2Å, which neither caused appreciable broadening nor a decrease in the transition probability. However, the data at different temperatures suggest that point defects may be responsible for the decrease in the transition probability.

On Future Directions in Pathology

1982 ◽  
Vol 40 ◽  
pp. 274-277
Author(s):  
Benjamin F. Trump ◽  
Irene K. Berezesky ◽  
Raymond T. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Clinical Pathology ◽  
Future Directions ◽  
Diagnostic Pathology ◽  
The Past ◽  
Transmission Electron ◽  
Organ Systems ◽  
The Many

The role of electron microscopy and associated techniques is assured in diagnostic pathology. At the present time, most of the progress has been made on tissues examined by transmission electron microscopy (TEM) and correlated with light microscopy (LM) and by cytochemistry using both plastic and paraffin-embedded materials. As mentioned elsewhere in this symposium, this has revolutionized many fields of pathology including diagnostic, anatomic and clinical pathology. It began with the kidney; however, it has now been extended to most other organ systems and to tumor diagnosis in general. The results of the past few years tend to indicate the future directions and needs of this expanding field. Now, in addition to routine EM, pathologists have access to the many newly developed methods and instruments mentioned below which should aid considerably not only in diagnostic pathology but in investigative pathology as well.

Cell Reactivity Pattern of the Guinea Pig Cecal Mucosa Evidenced by the ZIO Technique

1982 ◽  
Vol 40 ◽  
pp. 50-51
Author(s):  
Juan Mora-Galindo ◽  
Jorge Arauz-Contreras
Keyword(s):  
Guinea Pig ◽  
Phase Contrast ◽  
Osmium Tetroxide ◽  
Cell Types ◽  
Cell Reactivity ◽  
Transmission Electron ◽  
Neural Tissues ◽  
Maturation Stages ◽  
Zinc Iodide ◽  
Cecal Mucosa

The zinc iodide-osmium tetroxide (ZIO) technique is presently employed to study both, neural and non neural tissues. Precipitates depends on cell types and possibly cell metabol ism as well.Guinea pig cecal mucosa, already known to be composed of epithelium with cells at different maturation stages and lamina propria which i s formed by morphologically and functionally heterogeneous cell population, was studied to determine the pat tern of ZIO impregnation. For this, adult Guinea pg cecal mucosa was fixed with buffered 1.2 5% g 1 utara 1 dehyde before incubation with ZIO for 16 hours, a t 4°C in the dark. Further steps involved a quick sample dehydration in graded ethanols, embedding in Epon 812 and sectioning to observe the unstained material under a phase contrast light microscope (LM) and a transmission electron microscope (TEM).

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

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