Regensburg 2000 – scientific program
O 11.56: Poster
Monday, March 27, 2000, 19:00–22:00, Bereich C
The Adsorption of Maleic Anhydride on Si(100)-2x1: A Combined HREELS and NEXAFS Study — •T. Heller1, A. Lopez2, T. Bitzer2, N.V. Richardson2, and D. Schmeißer1 — 1BTU Cottbus, LS Angewandte Physik - Sensorik, Erich-Weinert-Str.1, 03046 Cottbus, Germany — 2School of Chemsitry, St. Andrews University, KY16 9ST UK
Due to the growing range of applications for organic materials considerable interest has been focused on the controlled growth of films on silicon substrates. Recently, it has been shown that ultra-thin oligimide films can be grown on Si(100)-2x1 with a direct Si-C linkage to the substrate. In this study, we have focused on the chemisorption of maleic anhydride (C4O3H2) on Si(100)-2x1. The combined HREELS data indicate that the adsorption of maleic anhydride on Si(100)-2x1 at low dosages occurs mainly through cycloaddition of the C=C bond to the dangling bonds of the Si-Si dimer analogous to the behaviour of ethene. The Si-Si dimer bonds are not involved in the chemisorption, as the continued observation of a 2x1 pattern in LEED shows. In the NEXAFS spectra, a π* resonance indicative of a C=C bond is absent upon exposure of the silicon substrate to maleic anhydride. At higher dosages, we observe chemisorbed maleic anhydride species, which are bonded to the Si surface atoms via a single Si-C linkage with preservation of the C=C double bond. In this case, the dissociated hydrogen bonds to one of the neighbouring Si atoms. Possible adsorption geometries will be discussed.