AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS2-ThM

Paper SS2-ThM10
Infrared Spectroscopy Study of Adsorption of Maleic Anhydride on Si(100)

Thursday, November 3, 2005, 11:20 am, Room 202

Session: Functionalization of Semiconductor Surfaces
Presenter: M. Niwano, Tohoku University, Japan
Authors: Y. Kimura, Tohoku University, Japan
H. Ishii, Tohoku University, Japan
M. Niwano, Tohoku University, Japan
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The adsorption of maleic anhydride on Si(100)-2Ã-1 has been investigated using infrared absorption spectroscopy (IRAS) in the multiple internal reflection (MIR) geometry. Previously, it has been suggested on the basis of HREELS data that at low coverages the adsorption of maleic anhydride occurs through cycloaddition of the C=C bond to the dangling bonds of Si-Si dimers, and at high coverage, maleic anhydride dissociatively adsorbs on the Si(100) surface. In the latter case, the dissociated hydrogen is bound to the Si surface atoms to form the Si-H bond, and the remaining fragments are bound to the Si surface atoms via a single Si-C linkage with retention of C=C double bond. In this study, we observe that an intense absorption peak appears at 2125 cm-1, while the peak due to the C=O stretching vibration is relatively weak. Previously the 2125-cm-1 peak has been assigned as being due to the Si-H stretching vibration mode. However, this peak is positioned at a slightly higher frequency than the monohydride peak that shows up around 2080 cm-1. Furthermore, we observe that the 2125-cm-1 peak appears even when the Si(100) surface is dosed with deuterium-substituted maleic anhydride. From these observations, we suggest that upon adsorption the five-membered ring of maleic anhydride is broken to generate the C=C=O bond and the dissociated molecule is bound to the surface Si atoms via the C-O-Si linkage. Ab initio cluster calculations indeed predicts that the C=C=O bond exhibits a vibration mode around 2120 cm-1. The present results indicates that maleic anhydride dissociatively adsorbs on the Si(100) surface in a rather complicated manner.