Electromechanical scale-bridging model for piezoelectric nanostructures

摘要

In past experimental studies, piezoelectric nanostructures have exhibited extraordinary behavior and unusual deformations. In order to establish the corresponding theoretical framework, a scale-bridging model, which takes into account surface piezoelectricity and the wave nature of electrons in ultra-narrow media by reflecting lattice distortions of atomic structures, has been proposed in this work. After applying this model to ZnO nanofilms with thicknesses ranging between 0.3 nm and 2.8 nm, asymmetric lattice distortions of the Zn- and O-terminated surfaces were observed and subsequently quantified using a lattice distortion factor. The material characteristics evaluated by using this model were found to be in good agreement with the results of first-principles calculations and corresponding experiments, and thus can be used for predicting the properties of thicker nanofilms. After bridging to the continuum scale, the data produced via finite element analysis significantly differed from the results obtained by the conventional model, owing to the unusual deformations caused by the nano-sized material properties and asymmetric surface characteristics. The obtained results help to achieve a better understanding of the properties of piezoelectric nanostructures with extraordinary characteristics and, therefore, can be used for the nanostructural design.