Chemical selectivity in photon-stimulated desorption of fluorine from silicon

Photon-stimulated desorption of ${\mathrm{F}}^{+}$ from Si(111) was studied with use of photon energies in the region of the Si 2p core level. Fluorinated surfaces with variable amounts of ${\mathrm{SiF}}_{\mathrm{x}}$ groups were prepared, and distinct photon-stimulated–desorption thresholds in the Si 2p region were observed for ${\mathrm{F}}^{+}$ desorption from SiF vs ${\mathrm{SiF}}_3$ surface groups. In addition, the angular distributions of the ejected ${\mathrm{F}}^{+}$ showed variations with respect to the Si(111) surface normal dependent on the bonding configuration, which were used to obtain local 2p absorption spectra for the individual ${\mathrm{SiF}}_{\mathrm{x}}$ groups.