Electron interactions

Electron-surface interactions

Scattering events

Elastic with atomic cores, DE=0

nearly isotropic at low energies (s -wave)

Inelastic Ž scattering with energy loss DE > E_gap

Bremstrahlung Ž contimuum photon emission

Excitation of core electrons Ž Auger electrons, characteristic X-rays. DE ł E_binding

Excitation of valence electrons Ž

Plasmons, low energy secondary electrons. DE(plasmons) = 7 - 25 eV (bulk), ť 0.7 E_bulk (surface)

Phonon excitation Ž heat

DE = n kT (n 25 meV at room temperature)

Excited valence electrons - secondary electron emission -useful in electron multipliers and photomultipliers

Keys to the use of electron spectroscopies

	Use characteristic energies to identify element
	Use short inelastic mean free paths for surface sensitivity

Mean escaped depth of electrons in solids and "universal" curve.

Further class notes on electron scattering

Updated October 3, 2000