Formation Mechanism and Properties of CdS-Ag2S Nanorod Superlattices

The mechanism of formation of recently fabricated CdS-Ag2S nanorod superlattices is considered and their elastic properties are predicted theoretically based on experimental structural data. We consider different possible mechanisms for the spontaneous ordering observed in these 1D nanostructures, such as diffusion-limited growth and ordering due to epitaxial strain. A simplified model suggests that diffusion-limited growth partially contributes to the observed ordering, but cannot account for the full extent of the ordering alone. The elastic properties of bulk Ag2S are predicted using a first principles method and are fed into a classical valence force field (VFF) model of the nanostructure. The VFF results show significant repulsion between Ag2S segments, strongly suggesting that the interplay between the chemical interface energy and strain due to the lattice mismatch between the two materials drives the spontaneous pattern formation.