Abstract
Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs core/shell nanowires brought by precursor flow directionality in the growth chamber. We observe the increase of bending with decreased core diameter. We further analyze the composition of a single nanowire and show through supporting finite element simulations that strain accommodation following the lattice mismatch between InP and InAs dominates nanowire bending. The simulations show the interplay between material composition, shell thickness, and tapering in determining the bending. The simulation results are in good agreement with the experimental bending curvature, reproducing the radius of 4.3 µm (±10%), for the 2.3 µm long nanowire. The InP core of the bent heterostructure was found to be compressed at about 2%. This report provides evidence of shape control and strain engineering in nanostructures, specifically through the exchange of group-V materials in III–V nanowire growth.
Highlights
One-dimensional nanostructures have been studied in the past decades for efficient applications in electronics, optics [1,2], electromechanics, energy [3,4], and more
We further explore the effects of geometry and composition on the strain relaxation through finite element simulation and find high correspondence to the experimental NW curvature by accurately accounting for NW shape, tapering in particular
COMSOL 5.3a was used for finite element simulations
Summary
One-dimensional nanostructures have been studied in the past decades for efficient applications in electronics, optics [1,2], electromechanics, energy [3,4], and more. Advanced control over nanomaterial shape provides a useful route for improving its electronic or optical properties This has been manifested in semiconductor nanowires (NWs) through several routes: (i) the growth of NWs with asymmetric cross section [5,6], where the NW cross-sectional shape was found to direct the light emission from the NW [5]; (ii) growth direction switching [7]; (iii) guided planar growth [8,9], opening up possibilities for straightforward electronic and optoelectronic NW integration; (iv) formation of unintentional nanostructures, such as quantum wires on NW facets, introducing unique optical and charge transfer properties [10,11]; and (v) growth of nanoflags [12], flakes/membranes [13,14,15], and selective area nanostructures [16,17]. We further explore the effects of geometry and composition on the strain relaxation through finite element simulation and find high correspondence to the experimental NW curvature by accurately accounting for NW shape, tapering in particular
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