New aspects in electron-stimulated desorption from ionic crystals

Electron-stimulated desorption of 7Li+ and 6Li+ ions desorbed from the LiF/Si(1 0 0) system has been studied by a time-of-flight method. It is observed that the positions of the kinetic energy distribution (KED) maxima of 7Li+ and 6Li+ strongly depend on the LiF layer deposition temperature. This observation was correlated with the LiF islands formation on the Si(1 0 0) surface, for which depending on the deposition temperature, an Li+ ion located on the top surface has different Madelung-energy. Two desorption components were separated. The first, dominating one, is very well reproduced by a smooth, slightly asymmetric bell-shaped function. The second component is characterized by specific oscillations in the Li+ KEDs curves. This feature, not observed for other ions desorbed, was attributed to the wave packet squeezing desorption mechanism.