Various Phenomena on PSI. Fundamental Processes Related to PSI. Physical Sputtering and Secondary Electron Emission.

Abstract

This paper describes the similarities and differences between physical sputtering and secondary electron emission from solids under ion bombardment. Emphasis is placed on the energy and angular distributions of emitted particles and particle emission statistics, as well as on total particle yield. The sputtering yield and secondary electron yield are strongly related to the nuclear stopping power and electronic stopping power of the solids for incident ions, respectively, whereas the energy distributions of sputtered atoms and secondary electrons are less influenced by these ions. Due to “collision cascade” and “electron cascade” before these atoms and electrons escape from the surface, both the energy distributions are similar to each other. However, the angular distribution of sputtered atoms shows under- and over-cosine distribution for low-energy and high-energy ions, respectively, whereas the angular distribution of secondary electrons is close to the cosine distribution, which results from the isotropic momentum distribution of secondary electrons inside the solids. For both, the statistical distribution for emission probabilities deviates from the Poission distribution in most cases.