Ab Initio Study of Octane Moiety Adsorption on H- and Cl-Functionalized Silicon Nanowires

Abstract

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.

Light Trapping in Silicon Arrays of Deep Subwavelength Features for Absorption of the Solar Radiation

“…The 4 n 2 limit is based on geometrical optics, and it pursues surface decoration of both sides of the thin film in order to increase the optical power in the film. More recently, it was suggested and demonstrated that the 4 n 2 limit can be exceeded if surface decoration with subwavelength structures is employed. − Various light trapping mechanisms were identified to produce broadband absorption enhancement of the sun power with surface subwavelength arrays: low optical impedance using arrays of nanocones and black silicon, − forward scattering by surface Mie resonators, increase in local density of states, excitations of Bloch modes, light trapping driven by light concentration and the utilization of nanolenses and light funnels, − excitations of localized Mie resonances, ,, and so forth.…”