Adsorption of 2,3-butanediol on Si(100)

The adsorption 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 andc0.97 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 -CHcgroups, in thecmolecule respectively. From the analysis of the valence band, the Si 2p, C 1s, and O 1s core-level spectra, we concludecthat the 2,3-butanediol molecule undergoes a cleavage of the O-H bonds, and is bonded to the surface by the oxygencatoms. The molecule shows no further fragmentation and probably forms a six-membered ring of the O-C-C-Osegment with the Si dimer atoms.