Modelling the growth of ZnO nanocombs based on the piezoelectric effect

F Fattahi Comjani,U Willer,W Schade,S Kontermann

doi:10.1063/1.4824616

Abstract

In this work a model for the growth of ZnO nanocombs based on the piezoelectric character of ZnO is presented that explains the periodic growth of nanowire branches on the polar +(0001) surface of a ZnO nanobelt as a self catalytic growth process. In this model the perturbation and elasticity theory are applied to approximate the induced mechanical strain and piezoelectric potential distribution in the nanobelt under the growth kinetics. To implement a quantitative simulation of the periodic growth of ZnO nanobranches the induced piezoelectric charges in the ZnO nanostructure are calculated. These are responsible for the structural transformation from a nanobelt into a nanocomb. A comparison with nanocombs that are synthesized using the vapor-liquid-solid method shows good agreement between experimental and theoretical results.

Highlights

ZnO with abundant configurations of nanostructures such as nanowires,1–3 nanaohelices,4,5 nanobelts,4–6 nanoplates,7 nanobridges,8 nanonails,8 nanosails,9 and nanocombs,10–13 is one of the most important functional semiconductor nanomaterials
In this work a model for the growth of ZnO nanocombs based on the piezoelectric character of ZnO is presented that explains the periodic growth of nanowire branches on the polar +(0001) surface of a ZnO nanobelt as a self catalytic growth process
It follows that the top polar +(0001) surface of the nanobelt has no homogenous Zn2+ ion density (see Fig. 6(b)).This suggests a self catalytic growth of ZnO nanowire branches on the polar +(0001) surface at the regions with higher positive charge density and more metal content compared to its vicinity

Summary

INTRODUCTION

ZnO with abundant configurations of nanostructures such as nanowires, nanaohelices, nanobelts, nanoplates, nanobridges, nanonails, nanosails, and nanocombs, is one of the most important functional semiconductor nanomaterials. In previous studies mechanisms for the growth of ZnO nanocombs have been proposed, which relate the formation of nanocombs with the self catalytic effect possibly due to the Zn cluster at the defective site on the polar +(0001) surface of the ZnO nanobelt or the enrichment of Zn at the growth front +(0001).. In previous studies mechanisms for the growth of ZnO nanocombs have been proposed, which relate the formation of nanocombs with the self catalytic effect possibly due to the Zn cluster at the defective site on the polar +(0001) surface of the ZnO nanobelt or the enrichment of Zn at the growth front +(0001).28 These mechanisms cannot explain the growth of parallel and evenly spaced nanowire branches of a nanocomb on the polar +(0001) surface of the backbone nanobelt, which may be important to control the growth process of nanocombs and to develop the nanoscale functional devices based on them. Our approach to explain the periodic geometrical shape of the ZnO nanocombs is given below

The perturbation theory

Theory of elasticity

Result of the electromechanical coupling in the ZnO nanobelt

MODEL OF GROWTH

CONCLUSIONS