Abstract

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Silicon is by far the most important semiconductor material in the microelectronic industry mostly due to the high quality of the Si/SiO₂ interface. Consequently, applications requiring chemical functionalization of Si substrates have focused on molecular grafting of SiO₂ surfaces. Unfortunately, there are practical problems affecting homogeneity and stability of many organic layers grafted on SiO₂, such as silanes and phosphonates, related to polymerization and hydrolysis of Si–O–Si and Si–O–P bonds.

These issues have stimulated efforts in grafting functional molecules on oxide-free Si surfaces, mostly with wet chemical processes. This review focuses therefore directly on wet chemical surface functionalization of oxide-free Si surfaces, starting from H-terminated Si surfaces. The main preparation methods of oxide-free H-terminated Si and their stability are first summarized. Functionalization is then classified into indirect substitution of H-termination by functional organic molecules, such as hydrosilylation, and direct substitution by other atoms (e.g. halogens) or small functional groups (e.g. OH, NH₂) that can be used for further reaction.

An emphasis is placed on a recently discovered method to produce a nanopattern of functional groups on otherwise oxide-free, H-terminated and atomically flat Si(1 1 1) surfaces. Such model surfaces are particularly interesting because they make it possible to derive fundamental knowledge of surface chemical reactions.