Electron induced dissociation of the NaCl(111) surface

Thin NaCl films, epitaxially grown under ultra-high vacuum conditions, were electron bombarded and analyzed by reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES) and quadrupole mass spectrometry (QMS). A comprehensive analysis of the results indicates that the impinging electrons cause surface dissociation, and consequently desorption of neutral chlorine and sodium at a rate governed by an Elovich-type mechanism. Simultaneously, the increasing coverage of carbon-oxygen compounds seem to indicate that metallic sodium clusters are formed and oxidized by gas phase residuals, to form a disordered inert layer at the surface. A mechanism of this process is suggested and the implications to subsequent epitaxial growth are discussed.