The dissociative adsorption of unsaturated alcohols on Si(111)-7x7

High-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations were used to investigate the attachment of allyl and propargyl alcohols on Si(111)-7 x 7 under ultra-high vacuum conditions. The HREELS spectra of chemisorbed allyl alcohol (AA) show the concurrent appearance of characteristic stretching vibrations of Si-H (2104 cm(-1)) and Si-O (795 cm(-1)) coupled with the retention of vibrational features of C=C stretching (1657 cm(-1)) and (Sp(2))C-H stretching (3012 and 3102 cm(-1)). These results clearly demonstrate the dissociative reaction nature via the hydroxyl group for the chemisorption of AA on Si(111)-7x7, which was further supported by XPS and DFT studies. A similar reaction pathway was found for propargyl alcohol (PA) adsorbed on the same Si(111)-7x7 surface. Our studies suggest that OH dissociation is highly favorable compared to [2+2]-like cycloadditions via C=C/C C for organic reactions on silicon surfaces, which may be explained by the large spatial separation between the adjacent adatom-rest atom pair on Si(111)-7x7. (C) 2008 Elsevier B.V. All rights reserved.