Transmission Electron Microscope Study of An Ordered Structure in GaAs0.5 Sb0.5 Grown By Molecular Beam Epitaxy

1987 ◽  
Vol 102 ◽  
Author(s):  
Y. E. Ihm ◽  
N. Otsuka ◽  
Y. Hirotsu ◽  
J. Klem ◽  
H. Morkoc
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Ordered Structure ◽  
Domain Structures ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Diffraction Patterns

ABSTRACTThe ordered structure in a (100) GaAs0.5 Sb0.5 epilayer grown by molecular beam epitaxy has been studied by transmission electron microscopy. Domain structures are observed in dark field images of superstructure reflections. The ordered structure is derived by the analysis of diffraction patterns taken from single domains. The ordered structure is described as an alternate stacking of As and Sb planes in the <111> direction of the FCC sublattice. The alternate stacking of As and Sb plane is directly observed by high resolution electron microscopy.

Unstained Biological Specimens in High Resolution Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 234-235
Author(s):  
M. K. Lamvik ◽  
J. M. Pullman ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Heavy Atom ◽  
High Resolution Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Structural Studies ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Scanning Transmission

Negative staining and high resolution shadowing have been extensively used for structural studies in electron microscopy. However, these techniques cover the specimen with a layer of heavy salt or metal, and hence do not allow determination of true mass distribution or localization of specific sites using heavy atom markers. A prerequisite for such structural studies is an examination of unstained specimens. For thin specimens dark field microscopy must be used to obtain adequate contrast. The scanning transmission electron microscope is preferred for such studies since elastic, energyloss, and unscattered electrons can be recorded and analyzed quantitatively to form images with a minimum of beam-induced damage.

On the interpretation of electron diffraction patterns from materials containing planar boundaries: the intergrowth tungsten bronzes

1990 ◽  
Vol 429 (1876) ◽  
pp. 91-117 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
General Interest ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Diffraction Patterns

Materials containing planar boundaries are of general interest and complete understanding of their structures is important. When direct imaging of the boundaries by, for instance, high-resolution electron microscopy, is impracticable, details of their structure and arrangement may be obtained from electron diffraction patterns. Such patterns are discussed in terms of those from intergrowth tungsten bronzes as specific examples. Fourier-transform calculations for proposed structures have been made to establish, in conjunction with optical-diffraction analogues, the features of the far-field diffraction patterns. These results have been compared with diffraction patterns obtained experimentally by transmission electron microscopy. The aim of the study, to show that the arrangement of the boundaries in these complicated phases can be deduced from their diffraction patterns without the need for high-resolution imaging, has been achieved. The steps to be taken to make these deductions are set out.

Defect Structures in Al-Ni-Rh Crystalline Approximants Studied by HREM and HAADF Techniques

2007 ◽  
Vol 561-565 ◽  
pp. 1353-1356 ◽  
Author(s):  
Wei Sun ◽  
Y.H. Chen ◽  
J.P. Wang ◽  
Z. Zhang
Keyword(s):  
Electron Microscopy ◽  
Structural Characteristics ◽  
Symmetry Plane ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Structural Defects ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

By means of a combination of high-resolution electron microscopy (HREM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) techniques, we have directly revealed that periodic arrangements in different manners for flattened hexagons constructed with atom columnar clusters can form two Al-Ni-Rh crystalline approximant phases. In contrast to periodic arrangements of flattened hexagons, configurations and distributions of various defects in these structurally-complicated alloy phases have been examined and their structural characteristics discussed. HREM observations clearly show that structural defects in Al-Ni-Rh crystalline approximants are of phason type and they are correlated with incorrect arrangements of atom columnar clusters. The distribution of high density planar defects can destroy the long-range periodicity in at least one direction in the pseudo decagonal symmetry plane. By means of the HAADF-STEM imaging technique, the existence of ill-formed atom columnar clusters in the core area of a linear defect, which is usually not visible in HREM observations, has been clearly revealed.

Origin of the superstructure elucidated by atomic resolution HAADF-STEM and HREM in the Ce10W22O81lanthanide tungstate phase

2018 ◽  
Vol 51 (2) ◽  
pp. 344-350 ◽  
Author(s):  
Loïc Patout ◽  
Abdelali Hallaoui ◽  
Thomas Neisius ◽  
Andrea P. C. Campos ◽  
Christian Dominici ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Atomic Resolution ◽  
Orthorhombic Unit Cell ◽  
Transmission Electron ◽  
New Information ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

The present paper provides new information on the attribution of the cationic sites of the orthorhombic Ce10W22O81crystal phase prepared in the CeO2–Ce2O3–WO3ternary system. Atomic resolution HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy) and HREM (high-resolution electron microscopy) investigations have highlighted the presence of two mixed columns of Ce and W cations along theaaxis that were previously assigned to pure W cations in the asymmetric unit. This discovery explains the presence of a commensurate superstructure doubling the orthorhombic unit-cell lengthao.

Tem Study of the Accidental Modulation of Mbe Grown AlxGal-x As

1986 ◽  
Vol 82 ◽  
Author(s):  
E.G. Britton ◽  
W.M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Long Range ◽  
Molecular Beam ◽  
Ordered Structure ◽  
Transmission Electron

ABSTRACTComposition modulations with a wavelength of -1-3 nm have been observed by transmission electron microscopy in nominally uniform AlxGa1-x As grown by molecular beam epitaxy. We describe the characterisation of this phenomenon and discuss its possible origins, in the light of the reported existence of a long range ordered structure.

scholarly journals The Structure of Al/GaAs Interfaces

1986 ◽  
Vol 77 ◽  
Author(s):  
Zuzanna Liliental-Weber ◽  
C. Nelson ◽  
R. Gronsky ◽  
J. Washburn ◽  
R. Ludeke
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Epitaxial Growth ◽  
Gaas Substrate ◽  
Molecular Beam ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Molecular Beam Epitaxy Chamber

ABSTRACTThe structure of Al/GaAs interfaces was investigated by high resolution electron microscopy. The Al layers Were deposited in a molecular beam epitaxy chamber with a vacuum base pressure of <1×10∼8 Pa. The GaAs substrate temperature varied during Al deposition from -30°C to 400°C. Deposition of Al on cold substrates £25°C resulted in epitaxial growth of (001) Al on (001) GaAs. Droplets of Ga were observed in samples with the substrate temperature at -30°C (1×2) and 0°C (c(2×8)). Postannealing of the last sample caused formation of the AlGaAs phase. Deposition of Al on hot substrates (150°C and 400°C) resulted in the formation of the AlGaAs phase, which separated (110) oriented Al from (001)GaAs.

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