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 CC 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 CC/CC 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.