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

Paper SS2-MoM8
Adsorption of Chiral Enantiomers of 2,3 butanediol on Si(100)

Monday, November 15, 2004, 10:40 am, Room 210C

Session: Functionalization of Semiconductor Surfaces
Presenter: K. Horn, Fritz-Haber-Institute der MPG, Germany
Authors: J.W. Kim, Fritz-Haber-Institute der MPG, Germany
M. Carbone, Universita Tor Vergata, Italy
M. Tallarida, Fritz-Haber-Institute der MPG, Germany
J.H. Dil, Fritz-Haber-Institute der MPG, Germany
K. Horn, Fritz-Haber-Institute der MPG, Germany
M.P. Casaletto, Instituto per lo Studio die Materiali Nanostrutturati ISMN, Italy
R. Flammini, Istituto de Metodologie Inorganiche e dei Plasmi CNR, Italy
M.N. Piancastelli, Universita Tor Vergata, Italy
Correspondent: Click to Email
The adsorption of the chiral L,L- and R,R as well as the achiral R,L enantiomer of 2,3-butanediol on a Si(1 0 0) surface has been investigated by photoelectron spectroscopy. The valence band spectra show features assigned to molecular orbitals of 2,3-butanediol by comparison with calculations, and the surface states of clean Si are removed. The Si 2p reveals core-level shifts with two new components at 0.24 and 0.97 eV from the bulk, which are assigned to Si-H and Si-O bonds, respectively. The C 1s core-level spectrum consists of two major peaks separated by 1.3 eV, which are attributed to carbon atoms in -CHOH and -CH3 groups, in the molecule respectively. From the analysis of the valence band, the Si 2p, C 1s, and O 1s core-level spectra, we conclude that the 2,3-butanediol molecule undergoes a cleavage of the O-H bonds, and is bonded to the surface by the oxygen atoms. The molecule shows no further fragmentation and probably forms a six-membered ring of the O-C-C-O segment with the Si dimer atoms. By using circularly polarized x-rays we were able to observe a sizeable circular dichroism in the C1s core level emission from the different enantiomers. We discuss this finding in its potential to identify the presence of chiral centers in adsorbed molecules.