Electron stimulated desorption: A critical review

Abstract

A critical review of the literature in the field of electron stimulated desorption is presented. The material is covered through December 1976. The literature on electron-induced ion desorption using bombarding electrons with energy <200 eV has been reviewed in detail several times. This review, therefore, concentrates on electron-induced desorption of ground state and excited state neutrals and the effect of electron bombarding energy in the energy range above several hundred eV. There is general agreement that ESD involves the direct interaction of the bombarding electron with the adsorbed species. Electronic transitions to anti-bonding modes result in the desorption of neutrals, excited state and ionic species. The cross sections are atomic in nature and vary from 10 -15 cm 2 to <10 -20 cm 2. The interactions and cross sections are relatively independent of the substrate material. The largest cross sections occur for weakly bound molecular species. Although there is agreement on the qualitative character of the interaction, there is very poor agreement on the quantitative cross section values. Very little information exists at all on direct measurements of neutral desorption and the effect of bombarding electron energy in the energy range above 500 eV. The material on neutral desorption is divided into three parts, namely experiments involving total pressure measurements, partial pressure measurements, and detection of desorbing excited state neutrals. The following section considers high energy data, independent of type of desorbing particle. Finally, new data concerning ion angular distributions in ESD is discussed.