Spontaneous Polarization-Induced Nanohelixes, Nanosprings, and Nanorings of Piezoelectric Nanobelts

TLDR

Growth of facet‑dominated free‑standing ZnO nanobelts is hindered by divergent surface energies from intrinsic polarization, which induces a spontaneous polarization across the nanobelt thickness. The study aims to control growth kinetics to produce nanobelt‑based structures whose surfaces are dominated by polarized ±(0001) facets. Rolling up single‑crystal nanobelts produces right‑handed helical nanostructures and nanorings as a result of minimizing the total energy from spontaneous polarization and elasticity. These polar‑surface‑dominated ZnO nanobelts provide an ideal platform for studying nanoscale piezoelectricity and polarization‑induced ferroelectricity, and they hold promise as one‑dimensional nanoscale sensors, transducers, and resonators.

Abstract

Growth of (0001) facet-dominated, free-standing, piezoelectric zinc oxide (ZnO) nanostructures is challenged by the divergence of the surface energy due to intrinsic polarization. By controlling growth kinetics, we show the success of growing nanobelt-based novel structures whose surfaces are dominated by the polarized ±(0001) facets. Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated ±(0001) surfaces, respectively, a spontaneous polarization is induced across the nanobelt thickness. As a result, right-handed helical nanostructures and nanorings are formed by rolling up single-crystal nanobelts; this phenomenon is attributed to a consequence of minimizing the total energy contributed by spontaneous polarization and elasticity. The polar-surface-dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization-induced ferroelectricity at nanoscale; and they could have applications as one-dimensional nanoscale sensors, transducers, and resonators.