scholarly journals Local structure analysis of amorphous materials by angstrom-beam electron diffraction

Microscopy ◽  
2020 ◽  
Author(s):  
Akihiko Hirata
Keyword(s):  
Electron Diffraction ◽  
Structure Analysis ◽  
Local Structure ◽  
Amorphous Materials ◽  
Rotational Symmetry ◽  
Diffraction Method ◽  
Beam Electron ◽  
Structure Information ◽  
Amorphous Structures ◽  
Global And Local

Abstract The structure analysis of amorphous materials still leaves much room for improvement. Owing to the lack of translational or rotational symmetry of amorphous materials, it is important to develop a different approach from that used for crystals for the structure analysis of amorphous materials. Here, the angstrom-beam electron diffraction method was used to obtain the local structure information of amorphous materials at a sub-nanometre scale. In addition, we discussed the relationship between the global and local diffraction intensities of amorphous structures, and verified the effectiveness of the proposed method through basic diffraction simulations. Finally, some applications of the proposed method to structural and functional amorphous materials are summarized.

Three-phase structure invariants and structure factors determined with the quantitative convergent-beam electron diffraction method

1999 ◽  
Vol 55 (2) ◽  
pp. 188-196 ◽  
Author(s):  
R. Høier ◽  
C. R. Birkeland ◽  
R. Holmestad ◽  
K Marthinsen
Keyword(s):  
Electron Diffraction ◽  
Phase Structure ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Structure Factors ◽  
Refinement Method ◽  
Three Phase ◽  
Phase Sensitive ◽  
Convergent Beam

Quantitative convergent-beam electron diffraction is used to determine structure factors and three-phase structure invariants. The refinements are based on centre-disc intensities only. An algorithm for parameter-sensitive pixel sampling of experimental intensities is implemented in the refinement procedure to increase sensitivity and computer speed. Typical three-beam effects are illustrated for the centrosymmetric case. The modified refinement method is applied to determine amplitudes and three-phase structure invariants in noncentrosymmetric InP. The accuracy of the results is shown to depend on the choice of the initial parameters in the refinement. Even unrealistic starting assumptions and incorrect temperature factor lead to stable results for the structure invariant. The examples show that the accuracy varies from 1 to 10° in the electron three-phase invariants determined and from 0.5 to 5% for the amplitudes. Individual phases could not be determined in the present case owing to spatial intensity correlations between phase-sensitive pixels. However, for the three-phase structure invariant, stable solutions were found.

Characterization of Amorphous Materials by Electron Diffraction and Atomistic Modeling

2000 ◽  
Vol 6 (4) ◽  
pp. 329-334 ◽  
Author(s):  
D.J.H. Cockayne ◽  
D.R. McKenzie ◽  
W. McBride ◽  
C. Goringe ◽  
D. McCulloch
Keyword(s):  
Molecular Dynamics ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Amorphous Materials ◽  
Atomistic Modeling ◽  
Amorphous Structures

AbstractThe technique of energy selected electron diffraction gives information about amorphous structures which can be used to characterize amorphous materials in terms of their structure. The diffraction data can be used to refine models obtained using molecular dynamics, resulting in physically reasonable models consistent with the diffraction data.

Enantiomorph identification of crystals belonging to the point groups 321 and 312 by convergent-beam electron diffraction

2007 ◽  
Vol 40 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Haruyuki Inui ◽  
Akihiro Fujii ◽  
Hiroki Sakamoto ◽  
Satoshi Fujio ◽  
Katsushi Tanaka
Keyword(s):  
Electron Diffraction ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
The Other ◽  
Zeroth Order ◽  
Beam Electron ◽  
First Order ◽  
Point Groups ◽  
Convergent Beam

The recently proposed CBED (convergent-beam electron diffraction) method for enantiomorph identification has been successfully applied to crystals belonging to the point groups 321 and 312. The intensity asymmetry of zeroth-order Laue zone and/or first-order Laue zone reflections of Bijvoet pairs is easily recognized in CBED patterns with the incidence along appropriate zone-axis orientations for each member of the enantiomorphic pair. The intensity asymmetry with respect to the symmetry line is reversed upon changing the space group (handedness) from one to the other. Thus, enantiomorph identification can be easily performed in principle for all crystals belonging to the point groups 321 and 312.

Convergent-beam electron diffraction studies of domains in tetragonal phase of lead zirconate titanate ceramics

1987 ◽  
Vol 45 ◽  
pp. 26-27
Author(s):  
M.L.A. Dass
Keyword(s):  
Electron Diffraction ◽  
Lead Zirconate Titanate ◽  
Tetragonal Phase ◽  
Diffraction Method ◽  
Rhombohedral Phase ◽  
Lead Zirconate ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Zirconate Titanate ◽  
Convergent Beam

Lead zirconate titanate Pb(ZrxTi(1-x))O3 (PZT) ceramics are ferroelectrics formed as solid solutions between PbTiO3 and PbZrO3. Among the different phases in the ferroelectric state, the primary ones are the Ti+4 rich tetragonal phase and the Zr+4 rich rhombohedral phase. The coexistence of both T and R phases at the boundary composition has been reported using the convergent beam electron diffraction method. In an attempt to characterize the ferroelectric domains in the different phases, a study on the tetragonal phase is reported here, as such an analysis is useful in identifying the phases at the phase boundary.The ceramic used in this study was prepared by conventional ceramic processing and the composition of the sample examined was Pb(Zr0.55Ti0.45)O3. The structure has been found to be tetragonal with lattice parameters a=4.0155Å and c=4.1033Å using X-ray diffraction studies of powder samples.

Radial distribution functions from diffracted electron intensities

1989 ◽  
Vol 47 ◽  
pp. 502-503
Author(s):  
J. Bentley ◽  
P. Angelini ◽  
P. S. Sklad ◽  
A. T. Fisher
Keyword(s):  
Electron Diffraction ◽  
Radial Distribution ◽  
Amorphous Materials ◽  
Dynamic Range ◽  
Diffraction Method ◽  
Distribution Functions ◽  
Amorphous Semiconductors ◽  
Radial Distribution Functions ◽  
Hydrogenated Silicon ◽  
Electron Microscopes

Many previous studies have shown the benefits of electronically recorded intensity profiles of electron diffraction patterns obtained with a transmission electron microscope (TEM). The technique, which is based on the scanning diffraction method developed by Grigson et al., avoids the complex procedures involved in making densitometer traces from film, greatly expands the dynamic range, and allows energy filtering to remove inelastically scattered electrons that have lost more than a few eV. Early applications to amorphous materials employed TEMs fitted with scanning systems and electrostatic filters below the projector lens. The main emphasis of the work of Graczyk et al. was on structural models for amorphous semiconductors such as silicon and germanium. However, a treatment for binary materials was developed and measurements were made for SiO2 and Ge-Te alloys. Cockayne et al. have recently extended these early techniques to modern 100 and 300 kV analytical electron microscopes, which when equipped with energy loss spectrometers and energy-dispersive x-ray analysis systems, do not require further major modification. Applications for which radial distribution functions have been determined from online measurements of energy-filtered selected area electron diffraction pattern intensity profiles have included amorphous thin films of carbon (a-C), germanium (a-Ge), boron nitride (a-BN), hydrogenated silicon (a-Si:H), silicon-carbon (a-Si1-xCx:H), and phosphorus- and boron-doped hydrogenated silicon.

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