Adsorption of some carbonyl and related compounds on Si(111)-7x7 surface

Abstract

The adsorption of some carbonyl (acetaldehyde, acetone, p-benzoquinone) and structurally related compounds (propargyl chloride, isopropyl isocyanide) on Si(111)-7C 7 was investigated by combining experimental (High-Resolution Electron Energy Loss Spectroscopy, HREELS; X-ray Photoelectron spectroscopy, XPS) and theoretical (Density Functional Theory, DFT) methods. Acetaldehydes were polymerized by the initiation of silicon surface dangling bonds, forming molecular chains containing ethane-1,1-dioxy blocks. Both acetone and propargyl chloride underwent an ene-like reaction, resulting in surface-bound enolate and terminal allene, respectively. p-Benzoquinone was attached to the surface by forming two Si-O covalent bonds. The binding mode was named [6+2]-like cycloaddition. Isopropyl isocyanide was adsorbed on Si(111)-7C 7 in two end-on configurations, with one bent and one linear molecular skeletons. The bent one is a radical species. Formation of donor-acceptor complexes between these two configurations were suggested by the anomalous vibrational peak shift.