The ability to manipulate the properties of Silicon nanowires (Si NWs) by controlling the chemistry of the Si surface is important for the realization of Si NW based devices for electronics and sensors. However, studies with 0D - 2D crystalline Si surfaces show that the presence of an insulating oxide overlayer is undesirable, because thick layers are electrically insulating and thin layers of the native oxide are electrically defective at the Si/Si-oxide interface.  Since a large proportion of the Si atoms of a NW are located at the surface compared to a 2D Si sample, the surface properties of the NWs are of a far greater importance in controlling the electron transport properties than for bulk Si samples.

Here, a two step chlorination / alkylation process was used to connect C1-C11 alkyl functionality to Si NW surfaces without intervening oxide.  The process functionalizes 50-100% of the Si sites on the Si NWs surface, most reasonably due to reduced steric effects.  The alkylated Si NW surfaces show high chemical stability in ambient conditions, as compared to similar molecules adsorbed on 2D substrates.  We attribute these observations to the lower steric hindrance effect on the Si NWs, as compared to 2D surfaces.  The alkylated Si NW surfaces show high stability against oxidation for more than one month under ambient conditions.  This fact is of practical importance when oxide free surfaces are required, e.g., for radial epitaxial on NWs to realize vertical P-N junctions for solar cells or radial Si/Ge super lattices for application in optoelectronics.

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