Origin of the Characteristic Electron Energy Losses in Aluminum

Abstract

The characteristic electron energy loss spectrum of aluminum has been measured by analyzing the energy distribution of 760-, 1000-, 1520-, and 2020-ev electrons scattered by an evaporated specimen through 90\ifmmode^\circ\else\textdegree\fi{}. Twelve loss peaks were observed, made up of combinations of elementary 10.3- and 15.3-ev losses. The former, the low-lying loss, is identified with the lowered plasma loss proposed by Ritchie, and the latter with the plasma loss proposed by Bohm and Pines and previously observed by many other workers. In measurements made with very thin evaporated targets, it was found that the low-lying loss changed considerably in position, as well as in intensity relative to the 15.3-ev loss. These changes, which are interpreted in terms of Ritchie's theory, definitely indicate that the low-lying loss is influenced by the surface layers of the specimen. As targets of high surface and volume purity could be prepared, it is concluded that results obtained by the present reflection technique, when examining loss behavior affected by surface phenomena, are superior to measurements of the characteristic loss spectrum of electrons transmitted through thin films.