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

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 30 K (CCl2F2 dose = 2.0 × 1014 molecules/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 120 eV to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120 eV photons are ~1.4 × 10− 18 and ~ 8.0 × 10− 18 cm2, respectively. Sequential F+ PSD spectra obtained by using continuous-time core-level photon-stimulated desorption spectroscopy in the photon energy range of 98-110 eV 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 98-110 eV, is mainly due to dissociative electron attachment and indirect dipolar dissociation induced by photoelectrons emitted from the silicon surface.

► Photolysis of CF2Cl2 molecules on Si by photons near the Si 2p edge was monitored. ► Excitation mechanisms for photolysis of CF2Cl2 molecules on Si are revealed. ► Photolysis cross section of the CF2Cl2-covered surface are determined. ► The surface fluorosilyl product during irradiation is SiF species.