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

Paper SS2-ThM11
Formation of Unsaturated Hydrocarbon Moieties on Hydrogen-terminated Si(111) by Grignard Reaction

Thursday, November 3, 2005, 11:40 am, Room 202

Session: Functionalization of Semiconductor Surfaces
Presenter: T. Yamada, RIKEN, Japan
Authors: T. Yamada, RIKEN, Japan
K. Shirasaka, RIKEN, Japan
M. Noto, RIKEN, Japan
H.S. Kato, RIKEN, Japan
M. Kawai, RIKEN and The University of Tokyo, Japan
Correspondent: Click to Email
Unsaturated hydrocarbon moieties, such as CH@SUB 2@=CHCH@SUB 2@-, CH:::C-,CH@SUB 3@CH=CHCH@SUB 2@- and CH@SUB 2@=CH- was deposited on hydrogen-terminated H:Si(111) by using the corresponding Grignard reagents (CxHyMgBr or CxHyMgCl) dissolved in tetrahydrofuran, followed by rinsing in CF@SUB 3@COOH solution. The product adsorbates were examined by vibrational methods with HREELS and internal multiple infrared reflection-absorption spectroscopy. It is anticipated that the unsaturated bonds within moieties may directly react with H:Si(111)@footnote 1@ and may be destroyed besides the desired bond shifting of C-Mg to C-Si. The CH@SUB 2@=CHCH@SUB 2@:Si(111) adsorbate was detected as the H-C= stretching and out-of-plane bending signals after the reaction in CH@SUB 2@=CHCH@SUB 2@MgBr/THF at 35°C for 5 min. The uptake of hydrocarbon moieties was 10% of surface Si with the remainder of originally terminating H atoms. The existence of C-Si stretching signal was revealed by using D:Si(111). Similarly in the cases of CH:::C- and CH@SUB 3@CH=CHCH@SUB 2@-, the unsaturated bonds were reserved. The double bond within CH@SUB 2@=CH- adsorbate was never observed, presumably because the C=C part would be close enough to the H-Si sites to undergo the direct adsorption. A notable result for better understanding of mechanism is that Grignard deposition just need one single H-Si site with no need for adsorption of MgX species in all cases. This was examined by isotope labeling in the rinsing procedure. Reservation of unsaturated bonds provides an approach to functionalized hydrocarbon moieties by addition reactions. Addition of NH@SUB 2@-, OH- or -COOH groups is prospective in surface modification with biochemical polymers with well-controlled adsorbate structure.@footnote 2@ @FootnoteText@ @footnote 1@M. R. Linford et al., J. Am. Chem. Soc. 117 (1995) 2145.@footnote 2@T. Yamada, et al., J. Chem. Phys. 121 (2004) 10660.