Electron emission holography at keV energies: Estimates of accuracy and limitations

Abstract

We consider the accuracy of holographic inversions of electron emission data at ~10 3 eV to yield atomic positions. Theoretical calculations for small clusters of 2-5 atoms in both single and multiple scattering show that self-interference effects may be present, and that forward-peaked scattering tends both to shift peaks by as much as 0.5-1.0 A from the true positions and to elongate images along forward-scattering directions. However, eliminating forward-peaked intensities before inversion significantly improves image quality.

The Study of Surface Structures by Photoelectron Diffraction and Auger Electron Diffraction

“…Additional spurious features that may arise in images due to the strength of the electronatom scattering and resultant self-interference effects have been pointed out by Thevuthasan et at. 162 By contrast, the multiple scattering defocusing illustrated in…”

“…Methods have been proposed for eliminating the observed distortions in atomic images due to both the anisotropic nature of the electron-atom scattering and the phase shift associated with the scattering by Saldin et al, 160 Tong et at., 161 and Thevuthasan et al 162 Preliminary tests of these methods are encouraging, but more applications to experimental data are needed to assess them fully. Further image distortions due to anisotropies in the electron emission process have been discussed,16o,161 and corrections for these also appear to be useful.…”

Photoelectron Diffraction and Synchrotron Radiation

“…The images so obtained indeed show structures near known atomic positions. However, considerable stucture is also observed at non-physical sites, and various procedures for improving image resolution and fidelity were introduced [29][30][31].…”

“…Radial distribution curves of the reconstucted real-space image are shown along the [011] nearest-neighbour direction, both as a function of distance in λ (right) and of the number of wavelengths (r/λ, left). The scattered-wave-included Fourier transform (SWIFT) method [30] was used in order to suppress the disturbing effects of the strong anisotropy in the complex scattering factor, which is known to affect both peak position and shape [29][30][31]. The right panel of Fig.…”

Fourier transform photoelectron diffraction and its application to molecular orbitals and surface structure

“…We computed the ARPEI?S theoretkal x curves with a cluster-model mukiplescattering code [32,33] using the Rehr-Albers separable propagator [34], and the phase shifts for electrons scattering Pt atoms are calculated with FEFF 7.0 [35,36] which considers relativistic effects, important for heavy elements like Pt. The Pt lattice constant was fixed at 3.923A.…”