AVS 49th International Symposium
    Surface Science Thursday Sessions
       Session SS+EL+OF-ThM

Paper SS+EL+OF-ThM11
Infrared Study of Adsorption of C@sub 6@H@sub 6@ onto Si(100)(2x1)

Thursday, November 7, 2002, 11:40 am, Room C-112C

Session: Reactions and Patterning of Organics on Silicon
Presenter: M. Niwano, Tohoku University, Japan
Authors: M. Shinohara, Tohoku University, Japan
H. Watanabe, Tohoku University, Japan
Y. Kimura, Tohoku University, Japan
H. Ishii, Tohoku University, Japan
M. Niwano, Tohoku University, Japan
Correspondent: Click to Email
The interaction of benzene with the (100) and (111) surfaces of silicon has proven to be an interesting model system for molecular adsorption on semiconductor surfaces. The adsorption of benzene on the Si(100)(2x1) surface has been expensively studied in recent years both experimentally and theoretically. Previous elaborate theoretical calculations predicted that adsorption of benzene onto the Si(100)(2x1) surface leads to two different adsorption structures: One corresponds to benzene adsorbed on top of a dimer row between two adjacent Si dimers. This structure has four C atoms of benzene bonded to four Si atoms from two adjacent dimers. The other corresponds to the benzene molecule that sticks on top of the dimer row and has two of its C atoms bonded to two Si atoms of a single surface dimer. However, there still is a controversy regarding which structure is more favored. In this study, we have investigated the adsorption of benzene C@sub 2@H@sub 6@ on the Si(100)(2x1) surface using infrared absorption spectroscopy (IRAS) in the multiple internal reflection geometry (MIR) and the so-called hybrid density-functional theory (DFT) to determine the most preferred adsorption structure of benzene on Si(100)(2x1) at room temperature. IRAS-MIR provides us with valuable information about the hydrogen bonding configurations on semiconductor surfaces. We analyzed IRAS spectra in the C-H stretching vibration region to determine the detailed adsorption structure of benzene. The central result is that benzene adsorbs in different manners depending on the surface coverage of benzene: at low coverage the molecule adsorb on the surface to favor the formation of benzene adsorbed on two adjacent dimers. On the other hand, at high coverage the molecule adsorb on the Si surface to generate benzene adsorbed on a single dimer. We also discuss the reason why the adsorption structure depends on surface coverage.