| Abstract
| - Transmission infrared spectroscopy (TIRS) has been used to investigate the surface-bound species formed inthe two-step chlorination/alkylation reaction of crystalline (111)-oriented Si surfaces. Spectra were obtainedafter hydrogen termination, chlorine termination, and reaction of the Cl−Si(111) surface with CH3MgX orC2H5MgX (X = Cl, Br) to form methyl (CH3)- or ethyl (C2H5)-terminated Si(111) surfaces, respectively.Freshly etched H-terminated Si(111) surfaces that were subsequently chlorinated by immersion in a saturatedsolution of PCl5 in chlorobenzene were characterized by complete loss of the Si−H stretching and bendingmodes at 2083 and 627 cm-1, respectively, and the appearance of Si−Cl modes at 583 and 528 cm-1. TIRSof the CH3-terminated Si(111) surface exhibited a peak at 1257 cm-1 polarized perpendicular to the surfaceassigned to the C−H symmetrical bending, or “umbrella” motion, of the methyl group. A peak observed at757 cm-1 polarized parallel to the surface was assigned to the C−H rocking motion. Alkyl C−H stretchmodes on both the CH3- and C2H5-terminated surfaces were observed near 2900 cm-1. The C2H5-terminatedSi(111) surface additionally exhibited broad bands at 2068 and 2080 cm-1, respectively, polarized perpendicularto the surface, as well as peaks at 620 and 627 cm-1, respectively, polarized parallel to the surface. Thesemodes were assigned to the Si−H stretching and bending motions, respectively, resulting from H-terminationof surface atoms that did not form Si−C bonds during the ethylation reaction.
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