Organic functionalization of silicon surfaces with alcohols, ketones and isothiocyanates

Abstract

The purpose of this thesis is to investigate organic functionalization of two silicon surfaces, Si(100)-2C 1 and Si(111)-7C 7, with three kinds of compounds, including alcohols, ketones, and isothiocyanates using HREELS, XPS and DFT theoretical calculations under UHV conditions. The interactions of allyl and propargyl alcohols with Si(111)-7C 7 were chosen as model systems to understand the selectivity and competition of unsaturated alcohols on silicon surfaces. The HREELS and XPS experimental results demonstrate that both allyl and propargyl alcohols are dissociatively bonded on Si(111)-7C 7 through the hydroxyl group, which are further supported by DFT theoretical calculations. These studies suggest that the OH dissociation reaction is highly favorable compared to [2+2]-like cycloadditions via C=C/Cb !C for organic reactions on silicon surfaces. The adsorption of several unsaturated ketones on silicon surfaces was investigated to explore the effect of molecular structures on the reaction selectivity. The different chemisorption activities for diacetyl and acetylacetone attached on Si(100)-2C 1 suggest that the surface reaction selectivity of multifunctional compounds can be controlled by precisely tailoring molecular structures of adsorbates, offering a great flexibility in organic functionalization of silicon surfaces. The binding of ethyl vinyl ketone on Si(111)-7C 7 was found to undergo [4+2]-like cycloaddition in a highly selective way. Methyl and allyl isothiocyanates are two typical molecules containing the N=C=S functional group. For their adsorption on Si(111)-7C 7, a [2+2]-like C=N cycloaddition is preferred over other competing cycloadditions via the C=S or C=C bond. The results shown in this thesis demonstrate that silicon surfaces can be efficiently modified by the attachment of various chemical functionalities, creating molecular templates for the fabrication of new hybrid organic/silicon devices. The incorporation of myriad and tunable organic functionalities to silicon surfaces gives much potential applications in semiconductor industries and many newly emerging areas.