AVS 47th International Symposium
    Semiconductors Tuesday Sessions
       Session SC+EL+OF-TuA

Paper SC+EL+OF-TuA7
A Comparative Study of the Bonding of N-Containing Heterocyclic Molecules to the Si(001) Surface

Tuesday, October 3, 2000, 4:00 pm, Room 306

Session: Organic Chemistry on Semiconductor Surfaces
Presenter: X. Cao, University of Wisconsin, Madison
Authors: X. Cao, University of Wisconsin, Madison
S.K. Coulter, University of Wisconsin, Madison
H. Liu, University of Wisconsin, Madison
J. Liu, University of Wisconsin, Madison
R.J. Hamers, University of Wisconsin, Madison
Correspondent: Click to Email
Recent studies of a variety of unsaturated hydrocarbons has lead to increased interest in understanding the factors controlling bonding of more complex organic molecules to silicon surfaces. By understanding the propensity for heterocyclic molecules to bond into various possible configurations, we are able to gain insight into the factors controlling selectivity in molecule-surface bonding. We have studied the adsorption of pyrrole and its partially-unsaturated analog, 3-pyrroline, onto the Si(001)-(2x1) surface using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy (STM). At 300 K, XPS spectra of pyrrole show a single, sharp N(1s) level, while FTIR spectra show that the molecule retains the high-frequency peaks that are characteristic of aromatic molecules; isotropic labeling studies show that attachment occurs through the N atom via cleavage of the N-H bond. These results show that pyrrole retains its aromatic character after bonding to the surface. In contrast, XPS and FTIR data for 3-pyrolline shows that it can bond through the N atoms or through its C=C bond via the surface equivalent of a [2+2] cycloaddition reaction. This study shows that molecules with aromatic rings show a strong preference for retention of this aromaticity, while molecules without aromaticity have more diverse chemical bonding configurations. Implications for understanding the attachment of other N-containing molecules to surfaces will be discussed.