Crystal-face dependence of low-energy ion scattering signals

Low-energy ion scattering (LEIS) on tungsten single crystals with different crystallographic orientations showed that only for the closest packed crystal face, the ion scattering signal originates completely from the outermost atomic plane. For various crystallographic orientations, we derived the contributions from the deeper atomic planes to the ion scattering signal, and found that for more open surface structures the deeper planes contribute significantly to the signal. For example, for the W(111) face, only 50% of the ion scattering signal is due to ions scattering from the outermost atomic plane. The influence of ion bombardment on the signal intensity of well-ordered crystalline surfaces was also studied, and it was found that ion bombardment of close-packed high-melting materials (e.g. W) at room temperature leads to a signal decrease of approximately 30% due to the sputter-induced roughness and disorder. The mobility of low-melting materials (e.g. Ag) during ion bombardment at room temperature results in a smaller sputter-induced roughness and disorder, and a small change in the ion scattering signal (5-10%). Surface cleaning by ion bombardment is a widely applied method, but thus requires a correction for the signal loss due to roughness and disorder when a quantitative analysis is performed. (C) 2001 Elsevier Science B.V. All rights reserved.