Evaluation of phonon scattering in electron diffraction using image plates and electron energy filtering

1995 ◽  
Vol 53 ◽  
pp. 134-135
Author(s):  
R. Høier ◽  
M.Y. Kim ◽  
J.M. Zuo ◽  
J.C.H. Spence ◽  
D. Shindo
Keyword(s):  
Electron Diffraction ◽  
Phonon Scattering ◽  
Imaging Plate ◽  
Phonon Modes ◽  
Thermal Diffuse Scattering ◽  
Energy Filtering ◽  
Specimen Holder ◽  
Kikuchi Lines ◽  
Electron Energy Filtering ◽  
Thermal Diffuse

There have been few studies of thermal diffuse scattering (TDS) by electron diffraction although this scattering is easily observed. The TDS intensity distribution is as a rule strongly anisotropic which can be ascribed to scattering from individual phonon modes. Results reported so far in the literature are all based on qualitative or semi-quantitative use of the observed intensity distributions. However, at present several new methods (energy filters, imaging plate, CCD, digitized film) are available to extract data for detailed quantitative interpretation. In the present work the Zeiss 912 Omega energy filtering microscope has been used, combined with the Fuji Imaging Plate and a low temperature specimen holder. This opens new possibilities both for the study of soft modes and other TDS phenomena related to phase transitions, and also static disorder and order-disorder effects. By comparison with synchrotron work on TDS , crystals may be very much smaller and count rates are much higher. However, multiple scattering and Kikuchi lines may complicate the interpretation unless thin samples are used.

Debye-Waller Factor Measurements by Quantitative Convergent Beam Electron Diffraction (CBED)

1997 ◽  
Vol 3 (S2) ◽  
pp. 1011-1012
Author(s):  
M. Saunders ◽  
A. G. Fox ◽  
P. A. Midgley
Keyword(s):  
Electron Diffraction ◽  
Waller Factor ◽  
Order Structure ◽  
Crystalline Materials ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Debye Waller Factor ◽  
Convergent Beam ◽  
Thermal Diffuse ◽  
Limited Accuracy

Quantitative CBED techniques are now capable of making low-order structure factor measure-ments with sufficient accuracy to study bonding effects in crystalline materials. The main limitation of these techniques has been identified as the accuracy with which one knows the Debye-Waller factor(s) (DWF(s)). Even where X-ray measurements exist, values have usually been determined at room temperature whereas we often want to perform our electron diffraction experiments at liquid nitrogen temperatures to reduce the effects of thermal diffuse scattering (TDS). Attempts to calculate theoretical DWF values have been shown to have limited accuracy when compared to experimental measurements.This has led to a search for new electron diffraction methods for DWF determination such as the use of HOLZ line segments, high-index systematic rows and electron precession patterns. The aim should be to measure the DWF(s) under identical conditions to those used for the charge density studies, e.g. the same sample thickness, temperature and microscope settings.

Electron spectroscopic diffraction at (111) silicon foils

1989 ◽  
Vol 47 ◽  
pp. 382-383
Author(s):  
L. Reimer ◽  
I. Fromm
Keyword(s):  
Energy Loss ◽  
Phonon Scattering ◽  
Bloch Wave ◽  
Foil Thickness ◽  
Energy Losses ◽  
Energy Filtering ◽  
Thin Foils ◽  
Kikuchi Lines ◽  
Lattice Planes ◽  
Electron Spectroscopic Diffraction

An electron diffraction pattern (EDP) consists of an overlap of patterns of all energy losses in the electron energy-loss spectrum (EELS). Electron spectroscopic diffraction (ESD) in an energy filtering electron microscope (EFEM) allows to separate the contributions of different energy losses to the unfiltered diagram observed in conventional TEM. We report about diffraction experiments with a Zeiss EM902 on (111) silicon foils which show how the EDP of single-crystal foils changes with increasing energy loss and foil thickness. An EDP normally contains the Bragg spots, diffuse streaks by electron-phonon scattering, excess and defect Kikuchi lines when the number of electrons striking the lattice planes is different from opposite sites, a system of excess (bright) Kikuchi bands with an intensity proportional to the probability ψψ⋆ of the Bloch wave field at the nuclei, and defect Ki-kuchi bands when the number of diffusely scattered electrons is equal on both sides of the lattice plane and the intensity becomes proportional to ΣIg.EDPs of thin foils show an increase of contrast of the Bragg spots and the thermal diffuse streaks when comparing an unfiltered (Fig.1a) and zero-loss filtered EDP (Fig.1b). Because the streaks are caused by elastic scattering, they can not be ob served with the plasmon loss (Fig.1c). Bragg spots are also observed at higher energy losses because all delocalized inelastic scattering processes with energy losses less a few hundred eV show intraband transitions which preserve the type of excited Bloch waves.

Observation of Soft Phonon Modes in 1T-TaS2 by means of X-ray Thermal Diffuse Scattering

2004 ◽  
Vol 73 (11) ◽  
pp. 3064-3069 ◽  
Author(s):  
Yo Machida ◽  
Takayasu Hanashima ◽  
Koichi Ohkubo ◽  
Kouji Yamawaki ◽  
Masahiko Tanaka ◽  
...  
Keyword(s):  
Diffuse Scattering ◽  
Phonon Modes ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Thermal Diffuse

scholarly journals Synchrotron x-ray thermal diffuse scattering probes for phonons in Si/SiGe/Si trilayer nanomembranes

MRS Advances ◽  
2016 ◽  
Vol 1 (48) ◽  
pp. 3263-3268
Author(s):  
Kyle M. McElhinny ◽  
Gokul Gopalakrishnan ◽  
Donald E. Savage ◽  
David A. Czaplewski ◽  
Max G. Lagally ◽  
...  
Keyword(s):  
Diffuse Scattering ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Elastic Anisotropy ◽  
Sige Layer ◽  
Reciprocal Space ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Recent Developments ◽  
Thermal Diffuse

ABSTRACTNanostructures offer the opportunity to control the vibrational properties of via the scattering of phonons due to boundaries and mass disorder as well as through changes in the phonon dispersion due to spatial confinement. Advances in understanding these effects have the potential to lead to thermoelectrics with an improved figure of merit by lowering the thermal conductivity and to provide insight into electron-phonon scattering rates in nanoelectronics. Characterizing the phonon population in nanomaterials has been challenging because of their small volume and because optical techniques probe only a small fraction of reciprocal space. Recent developments in x-ray scattering now allow the phonon population to be evaluated across all of reciprocal space in samples with volumes as small as several cubic micrometers. We apply this approach, synchrotron x-ray thermal diffuse scattering (TDS), to probe the population of phonons within a Si/SiGe/Si trilayer nanomembrane. The distributions of scattered intensity from Si/SiGe/Si trilayer nanomembranes and Si nanomembranes with uniform composition are qualitatively similar, with features arising from the elastic anisotropy of the diamond structure. The TDS signal for the Si/SiGe/Si nanomembrane, however, has higher intensity than the Si membrane of the same total thickness by approximately 3.75%. Possible origins of the enhancement in scattering from SiGe in comparison with Si include the larger atomic scattering factor of Ge atoms within the SiGe layer or reduced phonon frequencies due to alloying.

Differential quantitative analysis of background structure in energy-filtered convergent-beam electron diffraction patterns

2010 ◽  
Vol 43 (2) ◽  
pp. 280-284 ◽  
Author(s):  
Philip N. H. Nakashima ◽  
Barrington C. Muddle
Keyword(s):  
Electron Diffraction ◽  
Angular Frequency ◽  
Convergent Beam Electron Diffraction ◽  
Thermal Diffuse Scattering ◽  
Beam Electron ◽  
Background Structure ◽  
Diffuse Background ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Thermal Diffuse

Measurements of electronic structure in solids by quantitative convergent-beam electron diffraction (QCBED) will not reach their ultimate accuracy or precision until the contribution of the background to the reflections in energy-filtered CBED patterns is fully accounted for. Apart from the well known diffuse background that arises from thermal diffuse scattering of electrons, there is a component that has a much higher angular frequency. The present work reports experimental evidence that this component mimics the angular distribution of the elastically scattered electrons within each reflection. A differential approach to QCBED is suggested as a means of quantitatively accounting for the background in energy-filtered CBED data.

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