Ordinary and supernumerary resonant scattering of low energy electrons from the BiCu₂(111) surface alloy

Abstract

Electron intensity versus energy curves from the ordered substitutional BiCu 2 (111)-surface alloy, obtained with low energy electron microscopy (LEEM), show distinct unexpected intensity dips under normal incidence conditions. The dips above 10 eV are found to be characteristic of ordinary resonant scattering of electrons. Their positions represent resonant scattering into image potential states, involving scattering along G 10 and G 11 reciprocal lattice vectors. A detailed analysis of additional specular intensity dips at energies below 10 eV demonstrates that these originate from supernumerary resonant scattering, now also along lower symmetry directions, that should be forbidden in this energy range for the perfect crystal. LEEM is highly sensitive to detect these often neglected features which, if not properly disentangled or discarded, hamper its potential to extract the rich information about atomic positions and unoccupied electronic states encoded in very low energy electron scattering.

Quantum size stabilization of Ge3Pt nanofilms on Ge(001)

“…The pronounced minimum at 9.4 eV is at a too high energy for attribution to intensity losses due to inelastic excitations, including plasmon excitations. We rather assign the intensity loss to a natural consequence of bound-state resonances [20]. These resonances can occur when the following conditions are fulfilled:…”

“…The electron can travel along the surface below the vacuum level until it undergoes a reverse diffraction process which returns it into the specular beam. On its way along the surface, it may be scattered by defects or undergo inelastic losses, which both give rise to a loss of coherent intensity and, thus, to a minimum in the specular intensity [20]. Such processes are most prominent at low energies and during interaction with highly corrugated surfaces with an inherently high diffractive power.…”

Momentum-resolved photoelectron absorption in surface barrier scattering on Ir(111) and graphene/Ir(111)

“…The precise spatial dependence of the surface potential barrier plays an important role for the occurrence of two-dimensional electronic surface states. Surface barrier scattering of photoelectrons with low kinetic energy provides a very efficient tool for the investigation of details of the surface potential barrier [1]. By measuring interference patterns for photoelectrons in the momentum domain, Winkelmann et al [2] resolved specific quantum-mechanical effects of the surface barrier region of a Cu(001) surface.…”

Collective phenomena on metallic surfaces studied with scanning tunneling microscopy and low energy electron microscopy

“…Therefore, we alternatively looked at the Bi-modified Ni (111) surface. Bi deposition on the Ni (111) and Cu (111) surfaces has already shown to lead to a variety of dynamic processes [2][3][4][5][6][7]. Therefore, the Bi/Ni system was a perfect playground for our study, with the added value that we can further expand our knowledge of its surface phase diagram.…”

“…To observe the sample, we sometimes shine light through the vacuum system look-through windows, the lamp (5) has extended LED sources for easier illumination of the desired area. A valve (6) separates the preparation chamber from the main STM chamber (7), where the measurements are performed. The sample is positioned on a stage, controlled with a feed-through knob (8).…”