AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA9
Adsorption of Naphthalene on a Si(100)-2x1 Surface Investigated by Infrared Absorption Spectroscopy

Tuesday, November 4, 2003, 4:40 pm, Room 328

Session: Organic Functionalization of Semiconductor Surfaces
Presenter: M. Niwano, Tohoku University, Japan
Authors: K. Okamura, Tohoku University, Japan
H. Ishii, Tohoku University, Japan
Y. Kimura, Tohoku University, Japan
M. Niwano, Tohoku University, Japan
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Recently, adsorption of organic molecules on a Si surface has attracted a lot of interest in relation to possible application to organic-inorganic hybrid devices. Understanding of the adsorption process is required for the control of the structural and electrical properties of the interface between organic and inorganic materials. In this study, the adsorption of the naphthalene molecule, with two benzene-like rings fused together, onto the Si(100)-2x1 surface was investigated using infrared adsorption spectroscopy in the multiple internal reflection geometry. To determine the most preferred adsorption structure of naphthalene on Si(100)(2x1) at room temperature, we have carried out cluster calculations based on the hybrid density-functional theory (DFT), and compared the calculated C-H vibration frequencies with the experimental ones. The central result is that naphthalene adsorbs in different manners depending on the surface coverage of naphthalene, which is the same trend as observed for the adsorption of benzene on Si(100)(2x1). At low coverage the molecule adsorb in the bridging manner between two adjacent dimers. On the other hand, at high coverage the molecule adsorb on the Si surface so as to reduce the repulsive interaction between two adjacent naphthalene molecules adsorbed on the same dimer row. We discuss the reason why the adsorption structure depends on surface coverage, in comparison with the results of cluster calculations.