Electron momentum spectroscopy of surfaces

Electron momentum spectroscopy {[}binary (e,2e) spectroscopy] using transmission geometry is a unique experimental tool for imaging the electron momentum distribution in gas phase samples as well as in thin films. In a solid, the electron momentum distribution is related to the band structure. Development of the (e,2e) technique using a more versatile reflection geometry is attractive since a much wider range of surfaces could be studied. The design of a new reflection (e,2e) spectrometer is presented. It is based on a two-step scattering model in which an incident electron successively reflects and ejects a valence electron from the surface. The scattered and ejected electrons are detected in coincidence and their energies and momentum vectors are simultaneously determined using a high throughput 90 degrees truncated spherical electrostatic analyzer and position-sensitive detectors.