Abstract
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${}^{\ensuremath{\circ}}$ 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.
Highlights
Understanding the underlying formation mechanisms, controlling the morphologies, exploring their emergent properties, as well as exploiting their technological potentials are the central aspects of materials discovery of novel nanostructures.1–5 As an important class of specific materials examples, ZnO semiconductor nanorods typically possess hexagonal cross sections, and can be exploited for development of a rich variety of new generation optoelectronic devices
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
We present for the first time the remarkable contribution of stacking-fault-induced repeated polytypism on the formation of a unique hierarchical structure of ZnO nanorods, characterized by a hexagonal central trunk decorated with thin blades
Summary
Understanding the underlying formation mechanisms, controlling the morphologies, exploring their emergent properties, as well as exploiting their technological potentials are the central aspects of materials discovery of novel nanostructures. As an important class of specific materials examples, ZnO semiconductor nanorods typically possess hexagonal cross sections, and can be exploited for development of a rich variety of new generation optoelectronic devices. It has been predicted decades ago that screw dislocations in an ultrathin crystalline rod may induce a torque, lead to an elastic twist of the crystalline lattice, and eventually form a chiral pattern if one end of the rod is free to rotate.. It has been predicted decades ago that screw dislocations in an ultrathin crystalline rod may induce a torque, lead to an elastic twist of the crystalline lattice, and eventually form a chiral pattern if one end of the rod is free to rotate.14 Our detailed structural analysis shows that the blades are epitaxially initiated through reentrant-corner-mediated nucleation This finding demonstrates a previously unknown example of self-assembly process of hierarchical nanostructures controlled by polytypism, an intriguing new mechanism that may find broader applicability. We explore the novel optical properties of such hierarchical nanostructures
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