Using first-principles calculations based on density functional theory, we investigated the effects of surface functionalization on the energetic and electronic properties of hydrogenated and chlorinated silicon nanowires oriented along the <112> direction. We show that the band structure is strongly influenced by the diameter of the nanowire, while substantial variations in the formation energy are observed by changing the passivation species. We modeled an octane moiety absorption on the (111) and (110) surface of the silicon nanowire to address the effects on the electronic structure of the chlorinated and hydrogenated systems. We found that the moiety does not substantially affect the electronic properties of the investigated systems. Indeed, the states localized on the molecules are embedded into the valence and conduction bands, with no generation of intragap energy levels and moderated change in the band gap. Therefore, Si-C bonds can enhance protection of the hydrogenated and chlorinated nanowire surfaces against oxidation without substantial modification of the electronic properties. However, we calculated a significant charge transfer from the silicon nanowires to the octane moiety.
Keywords: band gap; charge density; density functional theory; electronic structure; octane moiety adsorption; passivation; silicon nanowire.