AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM11
Ideal Methyl Termination of the Si(111) Surface

Monday, November 15, 2004, 11:40 am, Room 210C

Session: Functionalization of Semiconductor Surfaces
Presenter: T. Yamada, RIKEN, Japan
Authors: T. Yamada, RIKEN, Japan
M. Kawai, RIKEN, Japan
A. Wawro, Polish Academy of Sciences, Poland
S. Suto, Tohoku University, Japan
A. Kasuya, Tohoku University, Japan
Correspondent: Click to Email
Si(111) surface ideally terminated by methyl (CH@sub 3@-) groups with a (1x1) periodicity was realized by Grignard reaction of Cl:Si(111)-(1x1). STM discerned a well-ordered (1x1) adlattice covering the Si(111) monoatomic step/terrace features as well as 3-fold-symmetric internal structure of protrusions corresponding to the CH@sub 3@ adsorbates. Reservation of all CH@sub 3@ internal bonds and formation of C-Si bond were confirmed by HREELS.@footnote 1@ Scanning tunneling spectroscopy (STS) exhibited diode-like I-V characteristics involving a new surface-originated occupied density of state at -1.6 eV. This unique electronic structure seems to be reflected on the electrochemical behavior in aqueous solutions. Measurement of vibrational decay time by laser sum-frequency generation is now in process for the internal modes. This finding of (1x1) adstructure led us to consider about the conditions of 2-dimensional ordering of organic moieties. Due to the C-Si covalent bonding, the adsorbates can hardly be mobile and self-assembling by inter-adsorbate interaction cannot be expected. Ordering should basically be originated by one-by-one termination of surface Si, and the adspecies should be accommodated within a hexagonal (1x1) unit cell of Si(111).@footnote 2@ We plan to deposit small moieties, such as CH:::C-, N:::C- and CF@sub 3@- by novel organic reagents. We also critically consider about deposition of long-chain alkyl adsorbates usually studied for purposes of application. The anchoring part of a long alkyl moiety sticks out of the (111) unit cell, and some of the neighborhood Si atoms should be terminated by small adsorbates (such as H and fragmented hydrocarbons). We attempted to approach this problem by investigating the surfaces formed by Grignard reaction with linear-chain alkyl groups (C4 and less). @FootnoteText@ @footnote 1@ T. Yamada et al., J. Am. Chem. Soc. 125 (2003) 8039.@footnote 2@ P. Allongue et al., J. Electroanal. Chem. 550 (2003) 161.