Effect of secondary electrons on the yield of electron-stimulated desorption of neutral atoms under differently localized core-level excitations in a substrate

Abstract

This paper reports on the results of a comparative analysis of the changes in the electron-stimulated desorption (ESD) yield of neutral particles from layers of alkali metal and Ba atoms deposited on the surface of a metal atop an oxygen (O/W, O/Mo) or germanium (Ge/W) film as a function of the incident electron beam energy E. The atomic yield q(E) is compared with the ionization cross sections of the core levels whose ionization potentials coincide with the ESD yield thresholds of the atoms. Three types of dependences q(E) are discussed, and the role of the secondary electrons generated in the electron-bombarded substrate for each type of the dependence of the ESD yield on E is elucidated. The analysis is based on the experimental studies performed by the authors in the recent years, starting from 1991. It is shown that the actual type of dependence q(E) is determined both by the actual localization of the atom excited by the electron beam and by the extent of localization of the core excitation resulting in ESD.