Atomic Structures of Planar Defects in Si and GaAs

1992 ◽  
Vol 262 ◽  
Author(s):  
S. Takeda ◽  
S. Muto ◽  
M. Hirata
Keyword(s):  
Experimental Evidence ◽  
Diffuse Scattering ◽  
Planar Defect ◽  
Dangling Bond ◽  
Hrem Image ◽  
Planar Defects ◽  
Atomic Structures ◽  
Gaas Matrix ◽  
Si Doped ◽  
Diffraction Patterns

ABSTRACTAtomic structures of planar defects in Si and GaAs have been studied by TEM. An HREM image of the edge of {113} planar defect has been obtained with <110> incidence. An analysis of the image has showed diat the edge consists of 5-, 6- and 7-membered rings without dangling bond. Anisotropie morphology of the defect could be understood from the model proposed in this report. Weak diffuse scattering and an extinction rule in diffraction patterns from the defect have been found. The experimental evidence has supported the model of the {113} defect.A planar defect on {111} in a heavily Si doped GaAs has been studied. The result has indicated that Si precipitates on the two {111} net planes inserted in the GaAs matrix.

Atomic Structures and Defects of As-Grown Nb1+αS2 Platelets on Nb Substrates

1992 ◽  
Vol 295 ◽  
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Crystal Structure ◽  
Grain Boundaries ◽  
Diffraction Pattern ◽  
Atomic Structure ◽  
Stacking Faults ◽  
Planar Defect ◽  
Defect Structures ◽  
Planar Defects ◽  
Atomic Structures ◽  
Octahedral Sites

AbstractThe interlocking of Nb1+αS2 platelets developed during sulfidation of Nb results in formation of a compact scale. The atomic structure and defects of these platelets were investigated using HREM. The resulting microstructure is very different from conventional microstructure consisting of polygonal grains and polyhedral grain boundaries because of the anisotropy of the crystal structure. The principal phase was identified as 3R-Nb2+αS2 intergrown with 2H-Nb1+αS2, or with some other arrangement of S-Nb-S slabs. The -S6- octahedral sites between two S-Nb-S slabs provide accommodation for extra Nb or foreign atoms and the large non-stoichiometry of Nb1+αS2. Stacking faults along the c axis account for the high density of planar defect structures observed within almost every platelet. Axial lattice fringe images and streaking in the diffraction pattern indicate that the planar defects are normal to the c direction.

Structure refinements in M7C3 (M=Cr,Fe) carbide

1990 ◽  
Vol 48 (4) ◽  
pp. 484-485
Author(s):  
A.Q. He ◽  
H.Q. Ye ◽  
G. van Tendeloo ◽  
K.H. Kuo
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Crystal Defects ◽  
Hrem Image ◽  
Beam Direction ◽  
Electron Microscopic ◽  
Antiphase Boundaries ◽  
Planar Defects ◽  
Contrast Method ◽  
Diffraction Patterns

The crystal defects in M7C3 (M=Cr,Fe) have been investigated by electron microscopy. The results show that there exist a lot of planar defects such as antiphase boundaries, and twin boundaries in it. According to Rouault et al., the structure of Cr7C3 is orthorhombic but based on a hexagnoal sublattice with a=0.701, b=1.214, c=0.452nm, i. e b/a=. For a perfect hexagonal sublattice the defects in {110} would be invisible both in electron diffraction patterns and in electron microscopic images when detected exactly along [001], So, these defects in M7C3 were observed by diffracted contrast method in which electron beam tilts a little from c axis or by HREM image with special beam direction but not [001] zone.e have found however in our sample the strcture of the M7C3 is probably orthorhombic but b/a≠3, such that no hexagnoal sublattice. A structure based on a non-hexagnoal lattice which produces twining is no longer invisble along [001] by HREM.Powder of M7C3 carbide was extracted by electricity chemistry from a cast-iron superalloy. The composition (wt) is: Cr-24.94%, Ni-20%, Mn-0.43%, Si-1.42%, S-0.017%, P-0.017%, C-0.41%. It was collected by carbon grid, and examined in JEOL 200CX.

Planar defects in ordered (Ga,In)P

1988 ◽  
Vol 46 ◽  
pp. 902-903
Author(s):  
S. McKernan ◽  
C. B. Carter ◽  
D. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Diffraction ◽  
Vapor Phase ◽  
Growth Direction ◽  
High Density ◽  
Ordered Structure ◽  
Planar Defects ◽  
Diffraction Patterns ◽  
Ternary Semiconductors ◽  
Anion Species ◽  
Metallic Vapor

The growth of ternary III-V semiconductors by organo-metallic vapor phase epitaxy (OMVPE) is widely practiced. It has been generally assumed that the resulting structure is the same as that of the corresponding binary semiconductors, but with the two different cation or anion species randomly distributed on their appropriate sublattice sites. Recently several different ternary semiconductors including AlxGa1-xAs, Gaxln-1-xAs and Gaxln1-xP1-6 have been observed in ordered states. A common feature of these ordered compounds is that they contain a relatively high density of defects. This is evident in electron diffraction patterns from these materials where streaks, which are typically parallel to the growth direction, are associated with the extra reflections arising from the ordering. However, where the (Ga,ln)P epilayer is reasonably well ordered the streaking is extremely faint, and the intensity of the ordered spot at 1/2(111) is much greater than that at 1/2(111). In these cases it is possible to image relatively clearly many of the defects found in the ordered structure.

Crystallographic Origin of the Alternate Bright/Dark Contrast in 6H-SiC and other Hexagonal Crystal HREM Images

1996 ◽  
Vol 2 (2) ◽  
pp. 63-78
Author(s):  
J.S. Bow ◽  
R.W. Carpenter ◽  
M.J. Kim
Keyword(s):  
Crystal Thickness ◽  
Material System ◽  
Hrem Image ◽  
Hexagonal Crystal ◽  
Cubic Crystals ◽  
Unit Cells ◽  
Crystal Model ◽  
Scattering Potential ◽  
Diffraction Patterns ◽  
Image Simulations

Alternating bright/dark anomalous subunitcell contrast in HREM images along or near the close-packed direction of 6H-SiC, Ti5Si3, α-Ti, and 4H-SiC, all of which are hexagonal, was examined using computer-generated crystal models, HREM image simulations, and digital diffractograms from the corresponding experimental images. The primary variables were crystal tilt and thickness. Crystal model projections showed that the scattering potential was smeared anisotropically within the unit cells by small crystal tilts, which reproduced the experimentally observed anomalous subunit-cell contrast modulations in the corresponding simulations. The effect increased with thickness, but it did not occur in exact zone axis simulations for any crystal thickness. Structural considerations indicated that the contrast resulted from tilt-induced violations of Gjonnes-Moodie dynamical extinctions and excitation of kinematically forbidden reflections in the imaging zone. Digital diffractograms from experimental HREM images confirmed their presence in the imaging zone diffraction patterns. These effects were absent in HREM images from cubic crystals in this material system because the structurally induced requisite kinematically forbidden reflections do not occur in the imaging zone.

On the Characterisatiopn of Order-Disorder in Ion-Irradiated Pyrochlore Compounds by Electron Scattering Methods

2008 ◽  
Vol 1122 ◽  
Author(s):  
Gregory R. Lumpkin ◽  
Karl R. Whittle ◽  
Mark G. Blackford ◽  
Katherine L. Smith ◽  
Nestor J. Zaluzec
Keyword(s):  
Electron Scattering ◽  
Diffuse Scattering ◽  
Zone Axis ◽  
Irradiation Damage ◽  
Nuclear Materials ◽  
Crystalline Fraction ◽  
Selected Area Electron Diffraction ◽  
Pyrochlore Compounds ◽  
Diffraction Patterns

AbstractSelected area electron diffraction patterns are routinely used to determine the effects of irradiation damage in nuclear materials. Using zone axis orientations, the intensities of Bragg beams change from a dynamical to kinematic-like state due to the presence of amorphous domains in the material. Such changes in beam intensities, together with the increased diffuse scattering from the increasing amorphous fraction, present a major obstacle to the determination of cation or anion disorder in the crystalline fraction.

Diffuse x-ray scattering from InGaAs/GaAs quantum dots

2003 ◽  
Vol 799 ◽  
Author(s):  
Rolf Köhler ◽  
Daniil Grigoriev ◽  
Michael Hanke ◽  
Martin Schmidbauer ◽  
Peter Schäfer ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Synchrotron Radiation ◽  
Diffuse Scattering ◽  
Data Evaluation ◽  
X Ray ◽  
X Ray Scattering ◽  
Gaas Matrix ◽  
Wetting Layers ◽  
Ray Scattering

ABSTRACTMulti-fold stacks of In0.6Ga0.4As quantum dots embedded into a GaAs matrix were investigated by means of x-ray diffuse scattering. The measurements were done with synchrotron radiation using different diffraction geometries. Data evaluation was based on comparison with simulated distributions of x-ray diffuse scattering. For the samples under consideration ((001) surface) there is no difference in dot extension along [110] and [-110] and no directional ordering. The measurements easily allow the determination of the average indium amount in the wetting layers. Data evaluation by simulation of x-ray diffuse scattering gives an increase of Incontent from the dot bottom to the dot top.

A High-Energy Monochromatic Laue (MonoLaue) X-ray Diffuse Scattering Study of KMnF3 using an Image Plate

1997 ◽  
Vol 30 (1) ◽  
pp. 16-20 ◽  
Author(s):  
A. Gibaud ◽  
D. Harlow ◽  
J. B. Hastings ◽  
J. P. Hill ◽  
D. Chapman
Keyword(s):  
Diffuse Scattering ◽  
High Energy ◽  
Experimental Conditions ◽  
X Ray ◽  
Image Plate ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Diffraction Patterns ◽  
Ray Scattering

The technique of high-energy monochromatic Laue X-ray scattering using image plates to record the diffraction patterns is presented. A tunable wiggler beamline is used as an X-ray source. It is shown that such experimental conditions present many advantages over conventional tube sources and photographic films. A study of diffuse scattering in the perovskite compound KMnF3 is presented to illustrate this in a qualitative way.

scholarly journals Disorder in pentachloronitrobenzene, C6Cl5NO2: a diffuse scattering study

2007 ◽  
Vol 63 (4) ◽  
pp. 663-673 ◽  
Author(s):  
Lynne H. Thomas ◽  
T. Richard Welberry ◽  
Darren J. Goossens ◽  
Aidan P. Heerdegen ◽  
Matthias J. Gutmann ◽  
...  
Keyword(s):  
Diffuse Scattering ◽  
Short Range ◽  
Scattering Data ◽  
X Ray ◽  
Monte Carlo Computer Simulation ◽  
X Ray Scattering ◽  
Scattering Study ◽  
The Mean ◽  
Diffraction Patterns ◽  
Local Relaxation

Monte Carlo computer simulation has been used to interpret and model observed single-crystal diffuse X-ray scattering data for pentachloronitrobenzene, C6Cl5NO2. Each site in the crystal contains a molecule in one of six different basic orientations with equal probability. However, no short-range order amongst these different orientations has been detected. The strong, detailed and very distinctive diffraction patterns can be accounted for almost entirely on the assumption of random occupancy of each molecular site, but with very large local relaxation displacements that tend to increase the neighbouring distances for contacts involving NO2...NO2 and NO2...Cl with a corresponding reduction for those involving Cl...Cl. The results show that the mean NO2...NO2 distance is increased by ∼ 0.6 Å, compared with that given by the average structure determination.

A study of the high-Cu Al–Cu–Co decagonal phase

1993 ◽  
Vol 8 (7) ◽  
pp. 1473-1476 ◽  
Author(s):  
B. Grushko
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Diffraction ◽  
Diffuse Scattering ◽  
Nonequilibrium State ◽  
Zone Axis ◽  
Decagonal Phase ◽  
Diffraction Patterns ◽  
Scanning Electron

The decagonal phase was studied by transmission and scanning electron microscopy in an Al62Cu24Co14 alloy annealed at 550–850 °C. The electron diffraction patterns of the decagonal phase exhibited weak quasiperiodic odd-n reflections in the [1-2100] zone axis corresponding to the equilibrated structure. The relative intensities of these reflections were significantly lower in the Al62Cu24Co14 than in the Al68Cu11Co21 decagonal phase. Diffuse scattering observed previously at the same positions can be related to a nonequilibrium state of the decagonal phase.

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