A very mild method was developed for the attachment of high-quality organic monolayers on crystalline silicon surfaces. By using visible light sources, from 447 to 658 nm, a variety of 1-alkenes and 1-alkynes were attached to hydrogen-terminated Si(100) and Si(111) surfaces at room temperature. The presence and the quality of the monolayers were evaluated by static water contact angles, X-ray photoelectron spectroscopy, and IR spectroscopy. Monolayers prepared by thermal, UV light, or visible light initiation were compared. Additionally, the ability of infrared reflection-absorption spectroscopy to study organic monolayers on silicon was explored. A reaction mechanism is discussed on the basis of investigations of the reaction behavior of 1-alkenes with silicon wafers with varying types and levels of doping. Finally, a series of mixed monolayers derived from the mixed solutions of a 1-alkene and an omega-fluoro-1-alkene were investigated to reveal that the composition of the mixed monolayers was directly proportional to the molar ratio of the two compounds in the solutions.

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This paper presents the first functionalization of silicon surfaces with well-defined, covalently attached monolayers containing saccharides. Two methods were used to this aim: a thermal method (refluxing in mesitylene) and a recently developed, extremely mild photochemical method (irradiation with 447 nm at room temperature). The results were analyzed by FT-IR and angle-resolved X-ray photoelectron spectroscopy. The use of a two-dimensional detector in ARXPS allows for unparalleled, subnanometer resolution in the determination of the elemental composition of monolayers. Even for monolayers with a total thickness of only approximately 1.5 nm, a clear elemental depth profile can be obtained. Such analyses display for sialic acid-containing monolayers that the mild photochemical attachment does not destroy the (rather fragile) sialic acid moiety and that the sugar is present at the top of the monolayer and thus available for biological interactions.