Monochromatic soft X-ray-induced reactions of CCl2F2 adsorbed on Si(111)-7 × 7 near the Si(2p) edge

Abstract

Continuous-time photoelectron spectroscopy (PES) and continuous-time core-level photon-stimulated desorption (PSD) spectroscopy were used to study the monochromatic soft X-ray-induced reactions of CCl2F2 molecules adsorbed on Si(111)-7×7 at 30K (CCl2F2 dose=2.0×1014molecules/cm2, ~0.75 monolayer) near the Si(2p) core level. Evolution of adsorbed CCl2F2 molecules was monitored by using continuous-time photoelectron spectroscopy at two photon energies of 98 and 120eV to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120eV photons are ~1.4×10−18 and ~8.0×10−18cm2, respectively. Sequential F+ PSD spectra obtained by using continuous-time core-level photon-stimulated desorption spectroscopy in the photon energy range of 98–110eV show the variation of their shapes with photon exposure and depict the formation of surface SiF species. The dissociation of CCl2F2 molecules adsorbed on Si(111)-7×7, irradiated by monochromatic soft X-ray in the photon energy range of 98–110eV, is mainly due to dissociative electron attachment and indirect dipolar dissociation induced by photoelectrons emitted from the silicon surface.