Developments in the measurement of spectral momentum densities with (e,2e) spectrometers

Abstract

The introduction of multiparameter high energy electron momentum spectroscopy (EMS) spectrometers, with high energy and momentum resolution and coincidence count rates, has made it possible to obtain detailed information on the electronic structure of condensed matter and surfaces. In particular it gives direct information on the spectral-momentum density of the material under study, which may be a single crystal, polycrystalline, or amorphous. The first such spectrometer, the Flinders University spectrometer, uses asymmetric kinematics in the measurement of the energies and momenta of the two outgoing electrons in the (e,2e) collision. The new ANU spectrometer uses symmetric kinematics and much higher energies. It is therefore less affected by deleterious multiple-scattering events. On the other hand the Flinders spectrometer is surface sensitive, whereas the ANU spectrometer is more bulk sensitive. Some aspects of EMS measurements of condensed-matter specimens and the performance of the two spectrometers are discussed.

Quantitative measurement of the spectral function of aluminum and lithium by electron momentum spectroscopy

“…1͒ that corresponds to the recoil momentum of the system ͑which, in the single particle picture, corresponds to minus the momen-tum of the struck electron.͒ The experimental apparatus and technique are described extensively elsewhere. 14,15 A thin (Ӎ30 Å) free-standing carbon substrate covering a number of 0.3 mm diameter holes in the target mount was sputtered by argon ion etching until some of the films broke. Polycrystalline metal specimens were prepared by evaporating aluminum and lithium onto these foils.…”

Direct measurement of spectral momentum densities of ordered and disordered semiconductors by high energy EMS

“…The experimental spectral function of crystalline Si has been measured by the solid state EMS group at the Australian National University for experimental information see Vos et al [6,7]. In Fig.…”

Influence of electron diffraction on measured energy-resolved momentum densities in single-crystalline silicon

“…It is described extensively elsewhere [8,12]. The spectrometer uses two-dimensional (energy and angle resolving) electrostatic energy analysers to measure efficiently the energy-resolved momentum densities.…”