Cross sections of electron stimulated desorption under technical vaccum conditions and 1 to 3 keV electron energies

Abstract

Cross sections are determined from the time constant of the decaying desorbed ion intensities. The vacuum chamber is evacuated with a sputter ion pump and a Ti getter pump to the 10 -6 Pa order. The target materials are Al, Fe and Cu. Incident electron energies are 1 to 3 keV. The experimental results show that (1) the energies of the emitted ions are about 4 eV, (2) the components are similar to residual gases in the vacuum chamber, and (3) the cross sections are in the 1.1x10 -17 to 2.1x10 -17 cm 2 range and are almost independentof incident electron energy and target material. These values are one or more orders of magnitude higher than those previously published by many researchers. These high cross section values are caused by the high adsorption rate on the target surface and by the thick adsorption layers resulting from the high residual gas pressure under technical vacuum conditions.