Electron stimulated desorption of oxygen ions from tungsten carbide

Abstract

Results on the adsorption and electron stimulated desorption of oxygen from tungsten carbide (WC) are presented and discussed. Desorbed ions were analyzed by a quadrupole mass analyzer (QMA) or a cylindrical mirror analyzer (CMA), the CMA also being used for in situ Auger electron spectroscopy (AES). The absolute total disappearance cross section of the O + ESD signal could be determined and was found to increase with decreasing initial coverage. The cross sections at 2 keV primary energy are 2 × 10 −18 cm 2 at θ = 0.05 and 9 × 10 −19 cm 2 at θ = 1. From the comparison of the O + ESD signal and the simultaneously recorded O-KLL AES signal it could be shown that at least two different adsorption states are present at the surface and that there is also electron induced conversion to a state with low ESD cross section. The dependence of the ESD yield on the primary electron energy, determined in the range from 80 eV to 2.5 keV, shows a maximum at about 300 eV.