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Surface topography dependent desorption of sodium chloride

Abstract Electron-stimulated desorption (ESD) of NaCl (001) surface was investigated in UHV by means of mass spectroscopy (MS) at various temperatures of the crystal. It was found that both atomic desorption components, i.e. Na and Cl atoms, show oscillatory dependence on the electron dose decaying gradually at the dose required for removal of several monolayers. These mass spectrometric measurements correspond well with periodically varying topography of the NaCl(001) cleavage faces during vacuum ultraviolet photon-stimulated desorption (PSD) observed previously by Höche et al. The analysis of our MS signal oscillations allowed us to study the dependence of the local desorption yield on the actual topography of the irradiated area. It is argued that the edges are acting as surface traps for the F-centres diffusing from the bulk to the surface of the irradiated crystal. The varying density of edges, therefore, can modulate the bulk and the surface defect density responsible for the efficiency of the desorption yield.