AVS 53rd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA1
Comparative Molecular Surface Functionalization of Silicon Surface Structures

Monday, November 13, 2006, 2:00 pm, Room 2004

Session: Functionalization of Semiconductor Surfaces
Presenter: J.N. Russell, Naval Research Laboratory
Authors: D.E. Barlow, Naval Research Laboratory
S.C. Erwin, Naval Research Laboratory
A.R. Laracuente, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
J.N. Russell, Naval Research Laboratory
Correspondent: Click to Email
Methods and chemistries to covalently attach organic molecules to single crystal semiconductor surfaces are the subject of considerable interest. While past functionalization studies on silicon have focused primarily on the (001) surface, the Si(114), oriented 19.5° between (001) and (111), has an equilibrium surface reconstruction comprised of parallel rows of dimers, rebonded atoms, and tetramers, with all the rows oriented along the same crystallographic direction. These structures make Si(114) an ideal surface for elucidating relationships between surface structure and organic reaction mechanisms on silicon. We have investigated cyclopentene and ethylene chemisorption on Si(114) using transmission Fourier transform infrared (FTIR) spectroscopy, scanning tunneling microscopy (STM) and density-functional-theory (DFT) calculations. The FTIR spectra are consistent with di-sigma bonding. A detailed analysis of the strong angular and polarization dependence of the ethylene C-H stretching mode intensities indicates it chemisorbs with the C-C bond axis parallel to the structural rows oriented along the [(1)10] surface direction. Using atomic-resolution STM, we identified three common adsorption structures located at the dimer, rebonded atom, and tetramer sites. In correlation with the FTIR and DFT results, these structures can be identified as [2+2] cycloaddition products, bridged rebonded atoms, and [4+2] cycloaddition products, respectively. The order of surface site reactivity is found to be rebonded atoms > dimers > tetramers. We found each ethylene/Si(114) adsorption structure has a characteristic C-H vibrational signature, which we used to identify the ethylene molecules that are chemisorbed on the step edges of the 4° off-axis (single domain) Si(001) surface.