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.

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.

On the Determination of Partial RDFs for Amorphous Materials

1993 ◽  
Vol 321 ◽  
Author(s):  
L. C. Qin ◽  
L. W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Amorphous Materials ◽  
Vitreous Silica ◽  
Scanning Transmission Electron Microscope ◽  
Distribution Functions ◽  
Electron Diffraction Data ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTRadial distribution functions (RDFs) for vitreous silica (V-SiO2) have been obtained from energy-filtered electron diffraction data obtained in the HB5 scanning transmission electron Microscope. Results have been compared with those obtained from high-resolution neutron diffraction experiments, and are in good agreement within experimental errors. It was found to be impractical to obtain partial RDFs for this material from combined neutron, X-ray and electron diffraction data, because the similarities in characteristics of X-ray and electron scattering cause indeter-Minacies. A criterion equation has been given to determine feasibility.

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.

Theory and practice of energy-filtered electron diffraction using the HB5 STEM

1992 ◽  
Vol 50 (1) ◽  
pp. 350-351
Author(s):  
L.C. Qin ◽  
A.J. Garratt-Reed ◽  
L.W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Amorphous Materials ◽  
Distribution Functions ◽  
Theory And Practice ◽  
Background Intensity ◽  
Intensity Data ◽  
Electron Diffraction Technique ◽  
Aperiodic Structure ◽  
Fast Electron Beam ◽  
Diffraction Patterns

Electron diffraction patterns obtained in TEM have long been an important part of microstructural characterizations. Certain materials, such as crystalline silicas, are amorphized in the fast electron beam of the TEM, and their aperiodic (metamict) structure is of interest. For amorphous materials, both elastically and inelastically scattered electrons contribute to the diffuse diffraction pattern. Analysis of aperiodic structure, however, requires intensity data from only elastically scattered electrons, and it is therefore it is necessary to obtain energy-filtered electron diffraction patterns. With the energy-filtered electron diffraction technique, the background intensity that is mainly due to inelastically scattered electrons is removed. This makes possible the derivation of radial distribution functions (RDFs) from collected electron diffraction intensity data for uniform aperiodic structures.

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.

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.

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