Molecular orientations of condensed Si(CH3)nCl4-n (0

Abstract

Near-edge X-ray absorption fine structure (NEXAFS) has been applied to the elucidation of the geometrical structures for condensed layers of Si(CH3)nCl4-n (0<or=n<or=4). For compounds containing both methyl and chlorine groups (n=1,2,3), it was observed that the NEXAFS at the Si K edge split into two sigma * resonances which correspond to the excitations from Si 1s to the unoccupied molecular orbitals of the S-Cl and Si-C bonds, respectively. The polarization dependence of the intensity of the two resonances was observed only for Si(CH3)3Cl. On the basis of the incidence-angle dependences of NEXAFS peak intensities, it was concluded that the Si-Cl bond in Si(CH3)3Cl is parallel to the surface and the average angle between surface normal and three Si-C bonds is about 43 degrees .