Desorption site-specificity and halogen minority sites on Si(1 1 1)

We identify the SiCl3 bonding geometry as the most desorptionactive site in x-ray photon-stimulated desorption (XPSD) of positive chlorine ions from chlorinated Si( 1 1 1) surfaces due to their much higher desorption cross-section in comparison to the on-top majority site. The novel combination of x-ray standing waves (XSW), XPSD and density functional theory (DFT) allows to quantitatively determine this trichloride adsorption geometry with high spatial resolution and to deduce the site-specific desorption cross-sections for Cl+ and Cl2+ ions, respectively. Additionally, these SiCl3 groups are shown to exhibit a preferential crystallographic orientation which is confirmed by both XSW and DFT. Moreover, the analoguous identification of desorption-active SiBr3 species for Br/Si(1 1 1) suggests a common physical origin of the site-specific desorption cross-sections.