X-ray initiated molecular photochemistry of Cl-containing adsorbates on a Si(1 0 0) surface using synchrotron radiation

X-ray initiated molecular photochemistry for SiCl₄ and CCl₄ adsorbed on Si(1 0 0) at ∼90 K following Cl 2p core-level excitation is investigated by photon stimulated ion desorption and ion kinetic energy distribution measurements. The Cl excitation of solid SiCl₄ induces the significant enhancement (∼900%) of the Cl⁺ yield, while the Cl excitation of condensed CCl₄ leads to a moderate enhancement (∼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 CCl₄ adsorbed on Si(1 0 0) (20-L exposure), the Cl⁺ yields at 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 CCl₄-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.