Ab initio atomistic prediction of charge separation in bent silicon nanostructures

Crystal lattice bending in which the lattice compresses and stretches differentially is a very common phenomenon that has frequently been observed in a variety of long nanostructures. The few studies carried out so far on this topic suggest that bending can significantly modify the properties of such nanostructures, and that they therefore deserve closer study. To explore such effects, we use a new strategy, named "cyclic replacement", to computationally produce bent silicon nanostructures. For these, ab initio density functional theory calculations predict charge separation with electrons and holes localized in different regions (varying with the lattice orientation), and a decreasing band gap is found with increasing curvature. We show that the underlying mechanism can be understood in terms of the different behavior of near-gap wave functions in the stretched and compressed atomic layers. Bent silicon nanostructures may be useful for solar-cell design where type II homojunctions are formed and charge separation could be facilitated by thermalization. © 2011 American Chemical Society.