BANDSTRUCTURE EFFECTS IN VeryLEED

In VeryLEED regime (below 30 eV) the spectra of electron reflection on the surfaces of crystals are dominated by the elastic effects of bulk E(k) above the vacuum level. This is revealed when the reflected intensity is found by matching on the surface the wave-function in vacuum (plane waves) and in the solid (Bloch waves). Following reflectivity features versus energy and incidence angle, one can extract accurate and explicit information on upper E(k): the energies of extremes of bands along any Brillouin zone direction, and even whole bands along symmetry lines. This is illustrated with a profusion of experimental examples. The theoretical background and the experimental technique are surveyed. Capabilities of VeryLEED to generate the upper bands for PES (IPES) are outlined.