Transmission infrared spectroscopy of methyl- and ethyl-terminated silicon(111) surfaces

Lauren J. Webb, Sandrine Rivillon, David J. Michalak, Yves J. Chabal, Nathan S. Lewis

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77 Citations (Scopus)


Transmission infrared spectroscopy (TIRS) has been used to investigate the surface-bound species formed in the two-step chlorination/alkylation reaction of crystalline (111)-oriented Si surfaces. Spectra were obtained after hydrogen termination, chlorine termination, and reaction of the Cl-Si(111) surface with CH3MgX or C2H5MgX (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 saturated solution of PCl5 in chlorobenzene were characterized by complete loss of the Si-H stretching and bending modes at 2083 and 627 cm-1, respectively, and the appearance of Si-Cl modes at 583 and 528 cm-1. TIRS of the CH 3-terminated Si(111) surface exhibited a peak at 1257 cm-1 polarized perpendicular to the surface assigned to the C-H symmetrical bending, or "umbrella" motion, of the methyl group. A peak observed at 757 cm-1 polarized parallel to the surface was assigned to the C-H rocking motion. Alkyl C-H stretch modes on both the CH3- and C 2H5-terminated surfaces were observed near 2900 cm -1. The C2H5-terminated Si(111) surface additionally exhibited broad bands at 2068 and 2080 cm-1, respectively, polarized perpendicular to the surface, as well as peaks at 620 and 627 cm-1, respectively, polarized parallel to the surface. These modes were assigned to the Si-H stretching and bending motions, respectively, resulting from H-termination of surface atoms that did not form Si-C bonds during the ethylation reaction.

Original languageEnglish
Pages (from-to)7349-7356
Number of pages8
JournalJournal of Physical Chemistry B
Issue number14
Publication statusPublished - Apr 13 2006

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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