Modification and chemical transformation of Si(1 1 1) surface

Modification of hydrogen-terminated Si(1 1 1) surfaces by hydrosilylation of activated alkenes and further chemical transformation of the modified surfaces is reported. A Si(1 1 1)–H surface was reacted with activated alkenes such as acrylate esters, acrylonitrile, and maleic anhydride under mild conditions to give modified surfaces with terminal functional groups. A modified surface with a terminal ester group was reduced by LiAlH4 to give a hydroxy-terminated surface, and the hydroxy-terminated surface was transformed to a bromo-terminated surface. XPS analysis revealed that the brominated surface (Si(1 1 1)–CH2CH2CH2Br) had 32% coverage with the 3-bromopropyl group. Ester and amide formation reactions were carried out on hydroxy- and carboxy-terminated Si surfaces by reaction with tert-butoxycarbonyl glycine, glycine tert-butyl ester, 2,2,2-trifluoroethanol and 4-trifluoromethylbenzyl alcohol in the presence of carbodiimide. XPS characterization indicated that the esters and amide were successfully formed with coverage ranging from 16% to 58%. Coverage ratios of octadecyl ester modified surfaces were also estimated by combination of surface reduction and gas chromatography analysis to be 25–35%.

Graphical abstractA Si(1 1 1)–H surface was reacted with activated alkenes under mild conditions to give modified surfaces with terminal functional groups. Further chemical transformation of the modified surfaces was reported. Coverage ratios of ester modified surfaces were estimated by combination of surface reduction and gas chromatography analysis.Figure optionsDownload full-size imageDownload as PowerPoint slide