Electron-beam-induced decomposition of ion bombarded calcium fluoride surfaces

Abstract

The effects of electron beams on the composition of ion bombarded calcium fluoride surfaces have been studied with Auger electron spectroscopy (AES), electron loss spectroscopy (ELS), and x-ray photoelectron spectroscopy (XPS). It was found with AES that when using typical AES excitation electron-beam parameters (5 keV, 5 μA), the calcium fluoride surface decomposed, resulting in the desorption of fluorine. The ELS and XPS measurements suggest that simultaneous with the desorption of fluorine from the surface, is the accumulation of calcium in a metalliclike state. Threshold measurements for the onset of fluorine desorption showed that AES analysis could be made without significant electron-beam effects by rastering a 2.5-keV, 0.05-μA electron beam over an area of 6×10−4 cm2, corresponding to a current density of 0.082 mA/cm2.