Anomalous electron absorption effects in metal foils: theory and comparison with experiment

1962 ◽  
Vol 269 (1336) ◽  
pp. 80-103 ◽  
Keyword(s):  
Fourier Coefficients ◽  
Stacking Faults ◽  
Formal Theory ◽  
Dynamical Theory ◽  
Anomalous Absorption ◽  
Physical Explanation ◽  
Absorption Effect ◽  
Metal Foils ◽  
Comparison With Experiment ◽  
Transmission Electron

The two-beam dynamical theory of electron diffraction in absorbing crystals has been applied to explain features of bend and thickness extinction contours and of images of stacking faults observed on transmission electron micrographs of metal foils. Inelastic scattering processes affect the intensities of the elastically scattered waves and give rise to 4 anomalous ’ transmission (Borrmann) effects. The formal theory takes account of these effects phenomenologically by the use of a complex lattice potential but ignores the contribution of the inelastically scattered electrons to the image. In the theory absorption is described by certain parameters ξ' 0 and ξ' g with dimensions of length. These parameters are determined by Fourier coefficients of the imaginary part of the potential in the same manner as the extinction distance ξ g is determined by the Fourier coefficient of the real part. A simple physical explanation of the ‘anomalous’ absorption effect is developed in terms of the two crystal wave fields. This explanation is particularly helpful in understanding details of bend and thickness contours and of images of stacking faults. The theory is at present phenomenological because the detailed mechanism of the absorption process is not understood. Nevertheless, comparison of the theory with observations enables the absorption parameters to be roughly estimated.

Characterization of Crystalline Defects Using CBED Techniques

1990 ◽  
Vol 48 (2) ◽  
pp. 520-521
Author(s):  
R. Pérez
Keyword(s):  
Fourier Coefficients ◽  
Stacking Faults ◽  
Small Region ◽  
Dynamical Theory ◽  
Convergent Beam Electron Diffraction ◽  
Zero Order ◽  
Image Contrast ◽  
Convergent Beam ◽  
Theoretical Simulations

Convergent beam electron diffraction (CBED) is a technique widely used for obtaining crystallographic information from a small region in a specimen. In recent years CBED technique have been mainly used for the symmetry characterization of perfect crystals. However, the study of crystals containing defects by CBED have received little attention in the literature1-4. The results presented in this communication explore some of the image contrast characteristics obtained in theoretical simulations of zero-order laue zone (ZOLZ) reflections. These calculations have been carried out for crystalline specimens wich contain dislocations or stacking faults. The theoretical simulations are based on the multibeam form of the dynamical theory using ato mic scattering factors reported by Doyle and Turner5. The Fourier coefficients of the lattice pottential were Debye-Waller corrected in all cases. Some of the most important parameters which have strong influence on image contrast have been explored. These include, the thickness of the specimen, the depth of defect in the specimen, the multibeam effects, the nature of the defects etc.

Structure of stacking faults in pyrite using TEM techniques

1992 ◽  
Vol 50 (1) ◽  
pp. 358-359
Author(s):  
Raja Subramanian ◽  
Kenneth S. Vecchio
Keyword(s):  
Lattice Structure ◽  
Stacking Faults ◽  
Covalent Bond ◽  
Group Symmetry ◽  
Iron Pyrite ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Contrast Analysis ◽  
Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

Atomic structure of stair rod misfit dislocations at the GaAs on Si(100) interface

1990 ◽  
Vol 48 (4) ◽  
pp. 342-343
Author(s):  
D. Gerthsen
Keyword(s):  
Lattice Constant ◽  
Atomic Structure ◽  
Spherical Aberration ◽  
Stacking Faults ◽  
Misfit Dislocations ◽  
Gaas On Si ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Intersection Line ◽  
Oriented Parallel

The prospect of technical applications has induced a lot of interest in the atomic structure of the GaAs on Si(100) interface and the defects in its vicinity which are often studied by high resolution transmission electron microscopy. The interface structure is determined by the 4.1% lattice constant mismatch between GaAs and Si, the large difference between the thermal expansion coefficients and the polar/nonpolar nature of the GaAs on Si interface. The lattice constant mismatch is compensated by misfit dislocations which are characterized by a/2<110> Burgers vectors b which are oriented parallel or inclined on {111} planes with respect to the interface. Stacking faults are also frequently observed. They are terminated by partial dislocations with b = a/6<112> on {111} planes. In this report, the atomic structure of stair rod misfit dislocations is analysed which are located at the intersection line of two stacking faults at the interface.A very thin, discontinous film of GaAs has been grown by MBE on a Si(100) substrate. Fig.1.a. shows an interface section of a 27 nm wide GaAs island along [110] containing a stair rod dislocation. The image has been taken with a JEOL 2000EX with a spherical aberration constant Cs = 1 mm, a spread of focus Δz = 10 nm and an angle of beam convergence ϑ of 2 mrad.

Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

1993 ◽  
Vol 51 ◽  
pp. 936-937
Author(s):  
Z. L. Wang ◽  
R. Kontra ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
L.F. Allard
Keyword(s):  
Volume Fraction ◽  
Local Density ◽  
Stacking Faults ◽  
Image Resolution ◽  
Defect Structures ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Point Image ◽  
Related Defect ◽  
Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

scholarly journals Oxidation-induced stacking faults in nitrogen-doped czochralski silicon investigated by transmission electron microscope

2004 ◽  
Vol 53 (2) ◽  
pp. 550
Author(s):  
Xu Jin ◽  
Yang De-Ren ◽  
Chu Jia ◽  
Ma Xiang-Yang ◽  
Que Duan-Lin
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Stacking Faults ◽  
Nitrogen Doped ◽  
Czochralski Silicon ◽  
Transmission Electron

Dislocations and stacking faults in stainless steel

1957 ◽  
Vol 240 (1223) ◽  
pp. 524-538 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Thin Sections ◽  
Partial Dislocations ◽  
Transmission Electron

Further experiments by transmission electron microscopy on thin sections of stainless steel deformed by small amounts have enabled extended dislocations to be observed directly. The arrangement and motion of whole and partial dislocations have been followed in detail. Many of the dislocations are found to have piled up against grain boundaries. Other observations include the formation of wide stacking faults, the interaction of dislocations with twin boundaries, and the formation of dislocations at thin edges of the foils. An estimate is made of the stacking-fault energy from a consideration of the stresses present, and the properties of the dislocations are found to be in agreement with those expected from a metal of low stacking-fault energy.

Defects in Germanium Nanocrystals Produced by Ion Implantation

2013 ◽  
Vol 709 ◽  
pp. 148-152
Author(s):  
Yu Juan Zhang ◽  
Lei Shang
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Implantation Dose ◽  
Defect Structures ◽  
High Temperature Annealing ◽  
Planar Defects ◽  
Transmission Electron ◽  
Microstructural Defects ◽  
Germanium Nanocrystals

Germanium nanocrystals (Ge-nc) were produced by the implantation of Ge+ into a SiO2 film deposited on (100) Si, followed by a high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) has been used to investigate the defect structures inside the Ge-nc produced by different implantation doses (1×1016, 2×1016, 4×1016 and 8×1016 cm-2). It has been found that the planar defects such as nanotwins and stacking faults (SFs) are dominant in Ge-nc (60%) for the samples with implantation doses higher than 2×1016 cm-2, while for the sample with an implantation dose lower than 1×1016 cm-2, fewer planar defects are observed in the Ge-nc (20%). The percentages of nanotwins in the planar defects are 87%, 77%, 67% and 60% in four samples, respectively. The twinning structures include single twins, double twins and multiple twins. We also found that there are only SFs in some nanocrystals, and in others the SFs coexist with twins. These microstructural defects are expected to play an important role in the light emission from the Ge-nc.

The mechanisms of plastic deformation of rapidly solidified Al3Ti and Al67Ni8Ti25 intermetallic compounds.

1988 ◽  
Vol 133 ◽  
Author(s):  
Vijay K. Vasudevan ◽  
Robert Wheeler ◽  
Hamish L. Fraser
Keyword(s):  
Room Temperature ◽  
Considerable Increase ◽  
Stacking Faults ◽  
Temperature Deformation ◽  
Deformation Microstructure ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
The Mean ◽  
Rapidly Solidified ◽  
Mechanisms Of Plastic Deformation

ABSTRACTThe dislocation structures in rapidly solidified Al3Ti with the DO22 structure and the ternary Al-25Ti-8Ni (at.%) alloy with the L12 structure deformed in compression in the temperature range of 25 to 800°C have been studied by transmission electron microscopy. The room temperature deformation microstructure of the Al3Ti compound is characterized by the presence of stacking faults/order twins on {111} planes bounded by partial dislocations with Burgers vector b=1/6<112], as reported by others. At intermediate temperatures, besides the stacking faults, slip is also observed as bands on the {001] plane delineated by dislocations with b=1/2<110] which bound APB's. At 600°C, the reported increase in ductility is associated here with additional slip on the {001)<110], {001)[100] and {001)[010] systems. Dislocations with b=<110] exist as pairs of partial dislocations with b=1/2<110] connected by APB's. The mean separation between the partials was measured to be 30 nm, corresponding to an APB energy of ≍32 mJ.m-2 on the (001) plane. Observations also indicate that the APB energy is anisotropic, i.e., is considerably higher on the {111} planes compared to the {001) plane. The deformation microstructure of the Al-25Ti-8Ni L12 alloy is characterized by slip of dislocations with b=<110> gliding on {111} planes, a major fraction of which exist as dipoles. Following deformation at 300°C, there is essentially no evidence of dissociation of these dislocations, although some dissociated dislocations on (001) having b=l/2<110> are also observed. With an increase in temperature, there is a considerable increase in dislocation activity and strong evidence for 1/2<110> dissociated dislocations is present.

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