Attenuation of excited electrons at crystal surfaces

Attenuation of the electron current determines surface sensitivity of electron spectroscopies. Pronounced energy and directional dependencies of the electron attenuation in crystals differ strongly from those commonly used for amorphous solids. Quantum descriptions of the electron attenuation can be obtained from the complex band structure of crystal surfaces at energies above the vacuum level. Contributions, specific for concrete processes, are obtained from theoretical description of photoelectron spectroscopy and of electron diffraction.