Abstract
Electron intensity versus energy curves from the ordered substitutional BiCu2(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 G10 and G11 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.
Highlights
Electron diffraction intensities at very low energies in low energy electron microscopy (LEEM) contain rich local information on the atomic positions and unoccupied electronic states [1,2,3]
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
When its correspondingly decreasing wavelength λ equals Λ, the condition given by equation (1) is fulfilled. This opens a new diffraction channel in which the electron resides in an eigenstate n of the image potential with an energy given by equation (1) depending on the energy εn(eV) = −0.85/(n + 0.21)2 [10], see figure 2. (For completeness we mention that the experimental locations of the image states on Cu(111) are at slightly lower energies [27]
Summary
Electron diffraction intensities at very low energies in low energy electron microscopy (LEEM) contain rich local information on the atomic positions and unoccupied electronic states [1,2,3]. This intensity dip located at about 13.5 eV is tentatively attributed to resonant scattering into the first and/ or second (or higher) order level(s) of the image potential via diffraction into the just opened G10 and equivalent channels with in-plane periodicity of 3.83 Å, see equation (1).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
