Site-specific ion desorption from condensed F3SiCD2CH2Si(CH3)3 induced by Si-2p core-level ionizations studied with photoelectron photoion coincidence (PEPICO) spectroscopy, Auger photoelectron coincidence spectroscopy (APECS) and Auger electron photoion coincidence (AEPICO) spectroscopy

Abstract

Ion desorption from condensed F3SiCD2CH2Si(CH3)3 induced by Si-2p core-level ionizations of the F3Si and the Si(CH3)3 sites (Si[F] and Si[Me]) was investigated using photoelectron photoion coincidence (PEPICO) spectroscopy, Auger photoelectron coincidence spectroscopy (APECS) and Auger electron photoion coincidence (AEPICO) spectroscopy. A Si-2p-F+ PEPICO peak appeared selectively in the Si[F]-2p region. Si-2p-H+ PEPICO peaks were, on the other hand, observed in both the Si[Me]- and Si[F]-2p regions. The structure of the Si-L23VV-Si[F]-2p Auger photoelectron coincidence spectrum (APECS) was quite different from that of the Si-L23VV-Si[Me]-2p APECS. Ab initio molecular orbital calculations qualitatively reproduced the measured APECSs. The peak positions in the Si-L23VV-F+ AEPICO spectrum were in good agreement with those in the Si-L23VV-Si[F]-2p APECS. The Si-L23VV-H+ AEPICO spectrum, on the other hand, showed no characteristic peaks. Based on these results we have concluded that the site-specific F+ desorption is stimulated by Si[F]-L23VV Auger processes, and that both the Si[Me]- and Si[F]-L23VV Auger decays are responsible for the non-site-specific H+ desorption.