X-ray standing wave study of alkali-metal/silicon interfaces

Abstract

The authors have investigated the adsorption of Rb and Cs on high-symmetry Si faces ((100)2*1, (111)7*7, (110)16*2 and (211)2*1) using the X-ray standing wave technique. Several substrate Bragg reflections were employed to locate the adsorbate using a triangulation method. Hollow-type sites are preferred at coverages close to saturation, although adsorbate-adsorbate interactions play an important role in some cases, and give rise to a coverage-dependent adsorption site change. In particular, in the cases of Si(111) and Si(211) the adsorption site changes with coverage (threefold hollow at saturation and on top at low coverages).