Microscopic view of the role of repeated polytypism in self-organization of hierarchical nanostructures

In this article we report our experimental observations that the repeated polytypism of wurtzite (WZ) and zinc-blende (ZB) phases induced by the fluctuation of the density of stacking faults can lead to the self-organized formation of ZnO hierarchical nanostructures characterized by a hexagonal central trunk decorated with thin blades. The blades epitaxially nucleate on the ZB stripes assisted by the reentrant corners at the ZB-WZ interfaces. Consequently, the blades keep a fixed angle with respect to the central trunk and resemble two sets of mutually intercalated propellers, each set possessing its own threefold rotational symmetry and being rotated for 60 degrees with respect to each other. We also study the optical properties of such novel structures, and show through numerical simulations that the blades provide the essential boundary conditions to establish the resonant electromagnetic responses in the hierarchical nanostructures. DOI: 10.1103/PhysRevB.87.085306