ELECTRON-STIMULATED DESORPTION FROM CAF2 - PENETRATION DEPTH OF ELECTRONS AND SAMPLE CHARGING

Two aspects of electron stimulated desorption experiments are covered in this contribution, namely the energy deposition of low energy electrons in CaF2 and the charging of the surface during irradiation. The stopping power for electron energies in the range from 50 eV to 5 keV is calculated using optical absorption data. Energy deposition curves and penetration depth vs. electron energy curves are given based on stopping power values and a Monte Carlo simulation of elastic scattering. Charging of the surface is described by means of an equilibrium between primary and secondary electrons. The sensitivity of the surface charging to stoichiometric changes is shown by monitoring the kinetic energy of desorbing F+ ions during metallization of the surface.