The dissociative adsorption of unsaturated alcohols on Si(1 1 1)-7×7

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(1 1 1)-7×7 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{double bond, long}C stretching (1657 cm^-1) and (sp²)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(1 1 1)-7×7, which was further supported by XPS and DFT studies. A similar reaction pathway was found for propargyl alcohol (PA) adsorbed on the same Si(1 1 1)-7×7 surface. Our studies suggest that OH dissociation is highly favorable compared to [2+2]-like cycloadditions via C{double bond, long}C/C{triple bond, long}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(1 1 1)-7×7.