X-ray initiated molecular photochemistry of Cl-containing adsorbates on a Si(100) surface using synchrotron radiation

Abstract

X-ray initiated molecular photochemistry for SiCl(4) and CCl(4) adsorbed on Si(100) at similar to 90 K following C1 2p core-level excitation is investigated by photon stimulated ion desorption and ion kinetic energy distribution measurements. The Cl 2p -> 8a(1)*, excitation of solid SiCl(4) induces the significant enhancement (similar to 900%) of the Cl(+) yield, while the Cl 2p -> 7a(1)* excitation of condensed CCl(4) leads to a moderate enhancement (similar to 500%) of the Cl(+) yield. The enhancement of Cl(+) yield at the specific core-excited states is strongly correlated to the ion escaped energy. Upon X-ray exposure for CCl(4) adsorbed on Si(100) (20-L exposure), the Cl(+) yields at 7a(1)* resonances decrease and new structures at higher photon energies are observed. Cl+ yields at these new resonances are significantly enhanced compared to those at other resonances. These changes are the results of desorption and surface reaction of the CCl(4)-Si surface complex due to X-ray irradiation. We have demonstrated that state-specific enhancement of ion desorption can be successfully applied to characterize the reaction dynamics of adsorbates adsorbed on surfaces by X-ray irradiation. (c) 2006 Elsevier B.V. All rights reserved.