A structure observation of GaAs micro crystal/Se-terminated GaAlAs interface for the quantum well box structure

ABSTRACTA selective growth of GaAs micro crystals was demonstrated on a Se-terminated GaAIAs surface by sequential supplies of Ga and As molecules for the quantum well box structure. After the growth, the surface consisted GaAs micro crystals with (111) facets and some Se clusters. The cross sectional investigations by the high resolution electron microscope revealed an epitaxial growth of GaAs micro crystals on the surface and a mixture of Ga2Se3 and A12Se3 layer formation at the interface of GaAs/Se-terminated GaAIAs. The selenidation process seems to be a reaction limited one. The Se cluster segregation could be avoided by selenidation in As molecule atmosphere.

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A Selective Growth of GaAs Microcrystals Grown on Se-Terminated GaAlAs Surface for the Quantum well Box Structure

MRS Proceedings ◽

10.1557/proc-283-765 ◽

1992 ◽

Vol 283 ◽

Author(s):

Toyohiro Chikyow ◽

Nobuyuki Koguchi

Keyword(s):

Electron Microscope ◽

High Resolution ◽

Quantum Well ◽

Epitaxial Growth ◽

Selective Growth ◽

Layer Formation ◽

Cross Sectional ◽

Resolution Electron ◽

Box Structure ◽

High Resolution Electron Microscope

ABSTRACTA selective growth of GaAs microcrystals was demonstrated on a Se-terminated GaAlAs surface. Ga molecules were supplied to the Se-terminated GaAlAs surface at first. The surface consisted of Ga droplets and bared Se-terminated GaAlAs surface. After the following As molecule supply to the surface, a selective GaAs microcrystal growth from Ga droplets was observed. The cross sectional investigations by the high resolution electron microscope revealed epitaxial growth of GaAs microcrystals with (111) facets and a possibility of (GaAl)2Se3, layer formation at the GaAs/Se-terminated GaAlAs interface.

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Interfacial structure and interfacial reactions at the MgO/Al2O3 interface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087793 ◽

1991 ◽

Vol 49 ◽

pp. 696-697

Author(s):

D. X. Li ◽

P. Pirouz ◽

A. H. Heuer ◽

S. Yadavalli ◽

C. P. Flynn

Keyword(s):

Electron Microscope ◽

High Resolution ◽

Molecular Beam ◽

Interfacial Structure ◽

Cross Sectional ◽

Resolution Electron ◽

High Resolution Electron Microscope ◽

Electron Microscope Image ◽

Image Simulations ◽

Standard Techniques

MgO films were deposited on the (sample A), (0001)Al2O3 (sample B), and the (sample C) planes of sapphire by Molecular Beam Epitaxy (MBE). Cross-sectional UREM specimens were prepared using standard techniques and examined in a top-entry JEOL 4000FX high resolution electron microscope. Image simulations were performed using the SHRLI programs developed by O'Keefe.

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An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072873 ◽

1973 ◽

Vol 31 ◽

pp. 486-487

Author(s):

Mihir Parikh

Keyword(s):

Electron Microscope ◽

High Resolution ◽

Cross Sections ◽

Resolving Power ◽

Peak Intensity ◽

Molecular Film ◽

Resolution Electron ◽

Dissociation Cross Section ◽

High Resolution Electron Microscope ◽

The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

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Computer-Controlled Hrem Alignment Using Automated Diffractogram Analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181415 ◽

1990 ◽

Vol 48 (1) ◽

pp. 532-533

Author(s):

G.Y. Fan ◽

O.L. Krivanek

Keyword(s):

Electron Microscope ◽

High Resolution ◽

The Other ◽

Full Information ◽

Resolution Electron ◽

Skilled Operator ◽

Automatic Alignment ◽

High Resolution Electron Microscope ◽

Computer Controlled ◽

Recorded Image

Full alignment of a high resolution electron microscope (HREM) requires five parameters to be optimized: the illumination angle (beam tilt) x and y, defocus, and astigmatism magnitude and orientation. Because neither voltage nor current centering lead to the correct illumination angle, all the adjustments must be done on the basis of observing contrast changes in a recorded image. The full alignment can be carried out by a computer which is connected to a suitable image pick-up device and is able to control the microscope, sometimes with greater precision and speed than even a skilled operator can achieve. Two approaches to computer-controlled (automatic) alignment have been investigated. The first is based on measuring the dependence of the overall contrast in the image of a thin amorphous specimen on the relevant parameters, the other on measuring the image shift. Here we report on our progress in developing a new method, which makes use of the full information contained in a computed diffractogram.

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