Rotational tomographic reconstruction of multiple in-line holograms

2000 ◽  
Vol 78 (11) ◽  
pp. 1005-1016 ◽  
Author(s):  
M R.A. Shegelski ◽  
T A Rothwell
Keyword(s):  
Scattering Theory ◽  
Optical Axis ◽  
Tomographic Reconstruction ◽  
Depth Resolution ◽  
Low Energy ◽  
Atomic Resolution ◽  
Low Energy Electron ◽  
Almost All ◽  
Theoretical Results ◽  
Axis Passing

Calculated electron in-line holograms, for the low-energy electron point source (LEEPS) microscope and based on scattering theory, give reconstructions that exhibit atomic resolution perpendicular to the optical axis. The depth resolution is not as sharp, and spurious peaks also result. We show that overall atomic resolution in the reconstruction of LEEPS in-line holograms can be obtained by using a tomographic approach. We examine a few reconstructions for holograms obtained by rotating the object about an axis passing through the object and parallel to the screen. We show that the reconstructions obtained from a small number of such "rotational tomographic holograms" can be combined in a manner such that almost all spurious peaks are eliminated and almost all atomic peaks are retained. The experimental implications of our theoretical results are discussed. PACS No.: 61.14Nm

ANALYSIS OF THERMAL VIBRATIONS AND INCOMMENSURATE LAYERS BY LOW ENERGY ELECTRON DIFFRACTION

1997 ◽  
Vol 04 (03) ◽  
pp. 469-478 ◽  
Author(s):  
W. MORITZ ◽  
J. LANDSKRON ◽  
T. GRÜNBERG
Keyword(s):  
Multiple Scattering ◽  
Scattering Theory ◽  
Low Energy ◽  
Multiple Diffraction ◽  
Low Energy Electron Diffraction ◽  
Anharmonic Vibrations ◽  
Recent Developments ◽  
Low Energy Electron ◽  
Thermal Vibrations

The multiple scattering theory of LEED is briefly reviewed, and recent developments concerning the analysis of thermal vibrations with LEED and the analysis of lattice modulations in incommensurate layers are discussed. Usually only isotropic thermal vibrations have been considered in LEED structure analyses. This restriction can be overcome by an extension of the theory to anisotropic and anharmonic vibrations, allowing not only a higher precision in the determination of structure parameters but also the study of dynamical processes with LEED. In the case of incommensurate layers the satellite reflections arise from multiple diffraction as well as from modulations in the adsorbate or substrate lattice. It is shown that an approximation can be introduced in the multiple scattering formalism to calculate the satellite intensities. The method can be applied to incommensurate layers as well as to higher order commensurate layers.

Tomographic reconstruction of multiple in-line holograms for multiple scattering in low energy electron holography

2001 ◽  
Vol 79 (1) ◽  
pp. 37-48 ◽  
Author(s):  
M R.A. Shegelski ◽  
M B Whitwick ◽  
R Holenstein ◽  
T A Rothwell
Keyword(s):  
Point Source ◽  
Multiple Scattering ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Low Energy ◽  
Energy Electron ◽  
Electron Holography ◽  
Atomic Cluster ◽  
Low Energy Electron ◽  
Object Relative

We generate simulated holograms for low energy electron point source (LEEPS) microscopy. For a given object (atomic cluster) we construct a number of different holograms by varying the position or the orientation of the object relative to the screen. We then compare the three-dimensional structures of the reconstructions obtained from these holograms using methods developed and reported in previous works. In this investigation, we focus on clusters for which multiple scattering must be taken into account. We report results for bcc-type clusters, a spiral configuration, and some random arrangements. We find that the methods employed give vastly improved reconstructions even when multiple scattering is important. PACS No.: 61.14Nm

scholarly journals Elastic scattering of low-energy electrons by OCS molecules.

2000 ◽  
Vol 53 (3) ◽  
pp. 399 ◽  
Author(s):  
M. H. F. Bettega ◽  
M. A. P. Lima ◽  
L. G. Ferreira
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Ab Initio Calculation ◽  
Low Energy ◽  
Low Energy Electrons ◽  
Exchange Approximation ◽  
Low Energy Electron ◽  
Theoretical Results

We report results from an ab initio calculation of low-energy electron scattering by OCS molecules. We used the Schwinger multichannel method with pseudopotentials at the fixed-nuclei static-exchange approximation to calculate elastic integral, differential and momentum transfer cross sections in the energy range from 5 to 50 eV. We compare our results with available theoretical results and experimental data. Through the symmetry decomposition of our integral cross section and eigenphase sum analysis, we found structures in the cross sections that may be interpreted as shape resonances for ∑, ∏ and Δ symmetries. We compared the results for OCS with our previous results on the e––CS2 collision. In particular, we found a similar behaviour in the shape of the symmetry decomposed cross sections of OCS and of CS2 when, for the latter, we sum over the ‘g’ and ‘u’ contributions.

Atomic resolution in lensless low-energy electron holography

1991 ◽  
Vol 67 (12) ◽  
pp. 1543-1546 ◽  
Author(s):  
Hans-Werner Fink ◽  
Heinz Schmid ◽  
Hans Jürgen Kreuzer ◽  
Andrzej Wierzbicki
Keyword(s):  
Low Energy ◽  
Energy Electron ◽  
Atomic Resolution ◽  
Electron Holography ◽  
Low Energy Electron
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