scholarly journals Analyzing Dislocations with Virtual Dark Field Images Reconstructed from Electron Diffraction Patterns

2014 ◽  
Vol 20 (S3) ◽  
pp. 1456-1457 ◽  
Author(s):  
E.F. Rauch ◽  
M. Véron
Keyword(s):  
Electron Diffraction ◽  
Dark Field ◽  
Diffraction Patterns

EELS of colloids in Mg+ implanted MgAl2O4 spinel

1994 ◽  
Vol 52 ◽  
pp. 980-981
Author(s):  
N. D. Evans ◽  
S. J. Zinkle
Keyword(s):  
Electron Diffraction ◽  
Elevated Temperatures ◽  
Lattice Parameter ◽  
Dark Field ◽  
Phase Identification ◽  
Dislocation Loops ◽  
Void Swelling ◽  
Electron Energy Loss Spectrometry ◽  
Diffraction Patterns ◽  
Electron Energy Loss

Because magnesium aluminate spinel (MgAl2O4) shows a strong resistance to void swelling during neutron irradiation at elevated temperatures, it is a candidate material for specialized applications in proposed fusion reactors. During implantation at 25°C with 2 MeV Mg+ ions to ∼2.8 × 1021 Mg+/m2, dislocation loops are formed at midrange depths (∼0.5 - 1.0 μm) on {110} and {111}. The microstructurc in the implanted ion region (∼1.5 - 2.0 μm) is shown in cross-section in Fig. 1. Within this implanted ion region, small features (4 - 10 nm diam.) were observed in dark field (DF) images using a spinel 222 reflection (Fig. 2). No evidence was found in electron diffraction patterns to suggest these features are (hexagonal) metallic Mg. However, in an earlier study, similar features in Al+ implanted spinel were identified by parallel electron energy loss spectrometry (PEELS) as metallic Al colloids. Phase identification of metallic Al within this spinel by electron diffraction is complicated because the lattice parameter of spinel (0.8083 nm) is almost exactly twice that of aluminum (0.4049 nm) and the phases are oriented cube-on-cube.

Distortion of the oxygen sublattice in pure cubic-ZrO2

2004 ◽  
Vol 19 (5) ◽  
pp. 1315-1319 ◽  
Author(s):  
C.M. Wang ◽  
S. Azad ◽  
S. Thevuthasan ◽  
V. Shutthanandan ◽  
D.E. McCready ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Molecular Beam ◽  
Film Growth ◽  
Dark Field ◽  
Oxygen Sublattice ◽  
Dark Field Imaging ◽  
Selected Area Electron Diffraction ◽  
Diffraction Patterns ◽  
Field Imaging ◽  
The Ideal

Multilayer films of pure ZrO2 and CeO2 were grown using molecular beam epitaxy on a yttria-stabilized zirconia (YSZ) substrate. Distinctive forbidden diffraction spots of (odd, odd, even) type were observed on the selected-area electron-diffraction patterns of the film. Dark-field imaging clearly revealed that these forbidden diffraction spots were solely due to the ZrO2 layers. Comparison of the electron diffraction pattern with that simulated by dynamical calculations suggest that the pure ZrO2 layers possess a cubic structure of space with the group P4 3m oxygen sublattice being displaced diagonally, rather than along the c axis as suggested for YSZ. Our results further suggest that the displacement of the oxygen from the ideal (¼, ¼, ¼) position might have been introduced during the film growth process.

Complementary Structural Information from Diffraction Patterns in STEM: Accurate Thickness Measurement with Pattern Matching

2001 ◽  
Vol 7 (S2) ◽  
pp. 224-225
Author(s):  
J. M. Zuo ◽  
Y.F. Shi
Keyword(s):  
Electron Diffraction ◽  
Structural Information ◽  
Accurate Determination ◽  
Thickness Measurement ◽  
Dark Field ◽  
Full Account ◽  
Precise Position ◽  
Significant Difference ◽  
Electron Microscopes ◽  
Diffraction Patterns

In this paper, we discuss the advantage of combining STEM imaging with diffraction. in addition, we present a set of accurately calculated convergent beam electron diffraction (CBED) patterns for Si, which highlights the sensitivity of electron diffraction to structure. The calculation takes the full account of crystal bonding by including known experimental structure factors in simulation. Such calculated patterns can be used for accurate determination of the sample thickness, crystal orientation and polarity (for acentric crystals). Calculations with and without crystal bonding show significant difference in calculated intensities, equivalent to a change in thickness about several nanometers for thick samples.The annual dark field (ADF) imaging mode in scanning transmission electron microscopes offers the unique advantage of combining high-resolution electron imaging and spectroscopy with diffraction. The large cutoff angle used in ADF imaging allows simultaneous recording of diffraction patterns for quantitative structural information, while ADF imaging gives the precise position of the probe and the image of the sample.

The Symmetry of Ordered Cubic γ-Fe2O3 Investigated by TEM

2006 ◽  
Vol 61 (6) ◽  
pp. 665-671 ◽  
Author(s):  
Klemens Kelm ◽  
Werner Mader
Keyword(s):  
Electron Diffraction ◽  
Spinel Structure ◽  
Intermediate Phase ◽  
Dark Field ◽  
Continuous Group ◽  
Cubic Phase ◽  
Bright Field ◽  
Space Groups ◽  
Octahedral Sites ◽  
Diffraction Patterns

Well-crystallized particles of cubic and tetragonal γ -Fe2O3 embedded in a Pd matrix were produced besides other oxides by internal oxidation of a Pd-Fe alloy in air. Particles of tetragonal γ -Fe2O3 consist of orientation domains with the c axes normal to each other. Particles of the ordered cubic γ -Fe2O3 appear single crystalline in bright field and in dark field images with reflections of the basic spinel structure. In dark field images enantiomorphous domains were observed using reflections of the ordered phase. From the analysis of electron diffraction patterns in the principal zone axes the description of ordered cubic γ -Fe2O3 in the enantiomorphous space groups P4132/P4332 follows without further presumptions. In the sequence from space group Fd3m of disordered cubic γ -Fe2O3 via P4132/P4332 of the ordered cubic phase to the pair P41212/P43212 of tetragonal γ -Fe2O3 a continuous group-subgroup relation can be derived. This relation shows that ordered cubic γ -Fe2O3 is an intermediate phase upon ordering of vacant octahedral sites towards tetragonal γ -Fe2O3

D-STEM: A Parallel Electron Diffraction Technique Applied to Nanomaterials

2010 ◽  
Vol 16 (5) ◽  
pp. 614-621 ◽  
Author(s):  
K.J. Ganesh ◽  
M. Kawasaki ◽  
J.P. Zhou ◽  
P.J. Ferreira
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Dark Field ◽  
Transmission Electron ◽  
Electron Diffraction Technique ◽  
Scanning Transmission ◽  
Stem Image ◽  
Diffraction Imaging ◽  
Diffraction Patterns

AbstractAn electron diffraction technique called D-STEM has been developed in a transmission electron microscopy/scanning transmission electron microscopy (TEM/STEM) instrument to obtain spot electron diffraction patterns from nanostructures, as small as ∼3 nm. The electron ray path achieved by configuring the pre- and postspecimen illumination lenses enables the formation of a 1–2 nm near-parallel probe, which is used to obtain bright-field/dark-field STEM images. Under these conditions, the beam can be controlled and accurately positioned on the STEM image, at the nanostructure of interest, while sharp spot diffraction patterns can be simultaneously recorded on the charge-coupled device camera. When integrated with softwares such as GatanTMSTEM diffraction imaging and Automated Crystallography for TEM or DigistarTM, NanoMEGAS, the D-STEM technique is very powerful for obtaining automated orientation and phase maps based on diffraction information acquired on a pixel by pixel basis. The versatility of the D-STEM technique is demonstrated by applying this technique to nanoparticles, nanowires, and nano interconnect structures.

Observation of Domains and Phase Separation in Hydrated Lipid Bilayers

1975 ◽  
Vol 33 ◽  
pp. 496-497
Author(s):  
S. W. Hui ◽  
D. F. Parsons
Keyword(s):  
Phase Separation ◽  
Transition Temperature ◽  
Electron Diffraction ◽  
Lipid Bilayers ◽  
Dark Field ◽  
Selective Area ◽  
Observation Area ◽  
Field Electron Microscopy ◽  
Diffraction Patterns ◽  
Selective Area Electron Diffraction

The domain structure and phase separation in lipid single bilayers were observed directly by selective area electron diffraction (SAED) and selected reflection dark field electron microscopy (SRDFEM), using an environmental stage for a Siemens Elmiskop IA. The specimens were viewed in a fully hydrated state in the temperature range between 0°C and 50°C. Below the transition temperature, three orders of a hexagonal pattern were recorded, whereas diffuse rings only were seen above the transition temperature.Selective area electron diffraction were done by restricting the illumination area to few micrometers in diameter, using a pointed filament and a 10 μm second condenser aperture. Below the transition temperature of dipalmitoylphosphatidylchoiine bilayers, differentially oriented diffraction patterns were distinguishable between adjacent membranes areas (domains) five micrometers apart. Occasionally, two or more superimposed patterns were recorded from the same area, indicating the observation area covered several domains.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

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