HREM of Electron Irradiated Quartz

1992 ◽  
Vol 279 ◽  
Author(s):  
L. C. Qin ◽  
L. W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Radial Distribution ◽  
Electron Irradiation ◽  
Crystalline State ◽  
Distribution Functions ◽  
Dynamic Evolution ◽  
Radial Distribution Functions ◽  
Transmission Electron ◽  
Electron Microscopes

ABSTRACTIn situ electron irradiation has been carried out in transmission electron microscopes to monitor the dynamic evolution of α-quartz during the transition to the metamict state from the crystalline state. Crystals of different orientations were examined. HREM images were digitized and Fourier transformed to monitor degradation of periodicities. The final uniform metamict structure was characterized by radial distribution functions obtained from energy-filtered electron diffraction.

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.

Estimation of radial distribution functions in electron diffraction experiments: physical, mathematical and numerical aspects

1999 ◽  
Vol 32 (5) ◽  
pp. 911-916 ◽  
Author(s):  
H. Nörenberg ◽  
R. Säverin ◽  
U. Hoppe ◽  
G. Holzhüter
Keyword(s):  
Electron Diffraction ◽  
Radial Distribution ◽  
Distribution Functions ◽  
Electron Diffraction Data ◽  
Radial Distribution Functions ◽  
Mathematical Methods ◽  
Interatomic Distances ◽  
Transmission Electron ◽  
Significant Difference ◽  
Polycrystalline Gold

Radial distribution functions (RDFs) can be obtained from transmission electron diffraction experiments. Polycrystalline gold specimens have been used to study how different mathematical methods extract the RDF information from electron diffraction data. Fourier transform (FT) and a maximum-entropy (ME) algorithm have been used in these calculations. Results obtained by the two methods are very similar and reproduce the interatomic distances accurately. Between the two methods, FT and ME, no significant difference could be found. ME calculations are very sensitive towards input parameters whereas the FT is a very robust algorithm. Calculations on reduced sets of experimental data with little error margin showed no improvement of resolution in the RDF calculated by ME.

Radiation-induced Chemical Disorder in Covalent Materials

2011 ◽  
Vol 1298 ◽  
Author(s):  
Manabu Ishimaru ◽  
Yanwen Zhang ◽  
William J. Weber
Keyword(s):  
Electron Microscopy ◽  
Crystalline State ◽  
Distribution Functions ◽  
Atomic Scale ◽  
Radial Distribution Functions ◽  
Transmission Electron ◽  
Chemical Disorder ◽  
Radiation Induced ◽  
Means Of Transmission ◽  
Amorphous Sic

ABSTRACTChemical disorder in ion-irradiated SiC and GaN has been examined by means of transmission electron microscopy. Radial distribution functions obtained by a quantitative analysis of electron diffraction intensities revealed that homonuclear bonds, which do not exist in the crystalline state, are formed in both ion-irradiated specimens. The origin of the homonuclear bonds is quite different between SiC and GaN. The constitute elements mix on the atomic-scale in amorphous SiC, while phase separation induced by irradiation is attributed to the formation of self-bonded Ga atomic pairs in amorphous/nanocrystalline GaN.

Energy-Filtered Electron Diffraction from Silica Thin Films

1992 ◽  
Vol 284 ◽  
Author(s):  
L. C. Qin ◽  
L. W. Hobbs
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Radial Distribution ◽  
Amorphous Materials ◽  
Scanning Transmission Electron Microscope ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Intensity Data ◽  
Scattered Electron ◽  
Silica Thin Films

ABSTRACTEnergy filtering has been applied to electron diffraction patterns to obtain electron scattering intensity data of single energy collected using a scanning transmission electron microscope. For amorphous materials, the technique permits reconstruction of radial distribution functions from elastically scattered electron intensity data; amorphous silica thin films have been analyzed in the present experiments. The radial distribution functions are characterized in terms of interatomic distances and are compared to neutron scattering results in the form of total correlation functions.

scholarly journals SUePDF: a program to obtain quantitative pair distribution functions from electron diffraction data

2017 ◽  
Vol 50 (1) ◽  
pp. 304-312 ◽  
Author(s):  
Dung Trung Tran ◽  
Gunnar Svensson ◽  
Cheuk-Wai Tai
Keyword(s):  
Electron Diffraction ◽  
Electron Scattering ◽  
Diffraction Data ◽  
Amorphous Materials ◽  
Fourier Transforms ◽  
Distribution Functions ◽  
Electron Diffraction Data ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Pair Distribution Functions

SUePDFis a graphical user interface program written in MATLAB to achieve quantitative pair distribution functions (PDFs) from electron diffraction data. The program facilitates structural studies of amorphous materials and small nanoparticles using electron diffraction data from transmission electron microscopes. It is based on the physics of electron scattering as well as the total scattering methodology. A method of background modeling is introduced to treat the intensity tail of the direct beam, inelastic scattering and incoherent multiple scattering. Kinematical electron scattering intensity is scaled using the electron scattering factors. The PDFs obtained after Fourier transforms are normalized with respect to number density, nanoparticle form factor and the non-negativity of probability density.SUePDFis distributed as free software for academic users.

Characterization of metamict and Glassy Lead Phosphates

1993 ◽  
Vol 321 ◽  
Author(s):  
A. N. Sreeram ◽  
L. W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Ion Implantation ◽  
Single Crystals ◽  
Field Emission ◽  
Radial Distribution ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Medium Range Order ◽  
Medium Range

ABSTRACTSingle crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence > 1027 e/M2 and an ionizing dose > 1014 Gy) were rendered Metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences between 5 × 1017/M2 - 2 × 1020/M2). Pb2P2O7 and PbO-P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions for metamict and glassy phosphates generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5) indicate significant alterations in the medium range order.

Convergent-beam electron diffraction at high spatial resolution

1992 ◽  
Vol 50 (2) ◽  
pp. 1152-1153 ◽  
Author(s):  
J W Steeds
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Bloch Wave ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Energy Filtering ◽  
Small Probe ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Convergent Beam

That the techniques of convergent beam electron diffraction (CBED) are now widely practised is evident, both from the way in which they feature in the sale of new transmission electron microscopes (TEMs) and from the frequency with which the results appear in the literature: new phases of high temperature superconductors is a case in point. The arrival of a new generation of TEMs operating with coherent sources at 200-300kV opens up a number of new possibilities.First, there is the possibility of quantitative work of very high accuracy. The small probe will essentially eliminate thickness or orientation averaging and this, together with efficient energy filtering by a doubly-dispersive electron energy loss spectrometer, will yield results of unsurpassed quality. The Bloch wave formulation of electron diffraction has proved itself an effective and efficient method of interpreting the data. The treatment of absorption in these calculations has recently been improved with the result that <100> HOLZ polarity determinations can now be performed on III-V and II-VI semiconductors.

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