Site-specific phenomena in Si:2p core-level photoionization of X3Si(CH2)nSi(CH3)3 (X=F or Cl, n=0–2) condensed on a Si(111) surface Original Research Article

We used photoelectron spectroscopy and the energy-selected-photoelectron photoion coincidence (ESPEPICO) method to study site-specific phenomena in the Si:2p photoionization of X3Si(CH2)nSi(CH3)3 (X=F or Cl, n=0–2) condensed on a Si(111) surface. The site-specific excitation and the occurrence of different chemical shifts at two Si sites were revealed in the total electron-yield spectra and the photoelectron spectra of F3Si(CH2)nSi(CH3)3 (n=1, 2), although they were not clearly revealed in those of Cl3SiSi(CH3)3. We conclude that these site-specific phenomena are easily observed in molecules in which the two Si sites are located far apart and in which electron migration between the two Si-containing groups does not occur. This was supported by our ab initio calculation. Site-specific fragmentation was revealed in the ESPEPICO spectrum of F3SiCH2CH2Si(CH3)3, although it was negligible for Cl3SiSi(CH3)3 and was less remarkable in F3SiCH2Si(CH3)3 than in F3SiCH2CH2Si(CH3)3. Site-specific fragmentation also occurred when the two Si sites were located far apart.