AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS3+EM-FrM

Paper SS3+EM-FrM1
A Comparative Study of [2+2] Cycloaddition Reactions of Organic Alkenes on Group IV Semiconductor Surfaces

Friday, October 29, 1999, 8:20 am, Room 604

Session: Reactions on Semiconductors
Presenter: R.J. Hamers, University of Wisconsin, Madison
Authors: R.J. Hamers, University of Wisconsin, Madison
J.S. Hovis, University of Wisconsin, Madison
S.C. Coulter, University of Wisconsin, Madison
C.M. Greenlief, University of Missouri, Columbia
Correspondent: Click to Email
Organic alkenes such as cyclopentene can bond to Si(001) and Ge(001) surfaces to produce monolayer organic films that are chemically homogeneous and structurally ordered. The bonding of these molecules to the dimerized Si, Ge, and C (diamond) surfaces is analogous to a class of ring-forming reactions known in organic chemistry as [2+2] cycloaddition reactions. While the bulk reactions involve the reaction of two alkene groups to form a four-member ring, the surface reactions involves two electrons from the organic alkene and two electrons from the ? orbital of the surface Si=Si, Ge=Ge, or C=C dimers. Solution-phase reactions of organic compounds via [2+2] processes are forbidden by orbital symmetry considerations and are therefore extremely slow. In order to better understand the nature of the analogous surface reactions, we have used infrared spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, and quantum chemistry methods to investigate the adsorption of cyclopentene and other simple alkenes on Si and Ge(001) semiconductor surfaces. Our results show that reactions of simple alkenes on Si(001) and Ge(001) surfaces are facile, producing ordered monolayers. Ab initio calculations for Si, Ge, and C clusters indicate that the reactions on Si and Ge surfaces are facile because of the ability of these surface dimers to tilt, facilitating a low-energy, low-symmetry pathway to adsorption on these surfaces. This talk will summarize our recent experimental and computational studies aimed at understanding the nature of cycloaddition reactions of organic alkenes on Group IV semiconductor surfaces. @FootnoteText@ This work was supported in part by the U.S. Office of Naval Research and the National Science Foundation.