Latest developments in (e,2e) on solids

Abstract

Recent progress in the application of the (e,2e) technique for elucidating the electronic structure of condensed matter is discussed. Particular emphasis is given to the description of a new third generation electron momentum spectrometer, which operates with an incident beam energy of 20-30 keV, uses asymmetric non-coplanar scattering kinematics with scattered electrons emerging at polar angles 8. = 14", and the ejected electrons emitted at 4e = 76". A range of scattered and ejected electron energies (20eV) and azimuthal angles (-18" 5 4, 5 18", -7 O < q5e -.rr 5 7O) are detected in parallel by means of two-dimensional position sensitive detectors. Software determines the energies and angles of the detected electrons, corrects for flight times through the analysers, and determines the separation energy and momentum for each event. With a 5nm amorphous carbon membrane, the true signal rate is 6Hz and the signal to background ratio is 1 with an incident current of 100nA. Without monocromation of the incident beam the energy resolution is l e v and the momentum resolution is 0.15au. The spectral momentum densities obtained for evaporated amorphous carbon are compared with theoretical results.

The (e,2e) spectroscopy, achievements and perspectives

“…For what concerns the application to solid targets, even though the first EMS experiment was performed on an amorphous carbon thin film (81, it is only recently (11112113) that it has been applied to the study of bands in solids. In particular, new multichannel spectrometers and improved energy resolution, recently achieved, have allowed for a complete reconstruction of the band structure in amorphous grafitic carbon (14). The presence of sp2 hybridisation accompanying the more usual sp3, was evidentiated by these measurements.…”