Nanowires bending over backward from strain partitioning in asymmetric core-shell heterostructures

Strain has always been a double-edged sword for heterostructure design, on the one hand constraining which materials can be combined to form coherent structures, but on the other hand providing a means to modify materials properties by strain engineering. In contrast to conventional planar heterostructures, three-dimensional nanostructures such as nanowires are highly flexible, allowing them to accommodate large strains and to bend. These traits open up a wide range of possibilities for realizing novel nanostructures and for engineering unconventional spatially varying strain fields in heterostructures.

Figure 1. (a) Schematic of a bent nanowire consisting of a GaAs core with a lattice-mismatched Al0.5In0.5As shell on the outer side of the core. (b-c) Scanning electron micrographs of nanowires with the structure from (a) which are (b) bent completely over backward to contact the substrate and (c) controllably bent to contact a neighboring nanowire.

In this work, we realize arrays of extremely and controllably bent nanowires comprising lattice mismatched and highly asymmetric GaAs/Al0.5In0.5As core-shell heterostructures. Strain sharing across the nanowire heterostructures is sufficient to bend vertical nanowires over backward to contact either neighboring nanowires or the substrate itself, presenting new possibilities for designing nanowire networks and interconnects. Photoluminescence spectroscopy on bent nanowire heterostructures reveals that spatially varying strain fields induce charge carrier drift toward the tensilely strained outside of the nanowires, and that the polarization response of absorbed and emitted light is controlled by the bending direction. This unconventional strain field is employed for light emission by placing an active region of quantum dots at the outer side of a bent nanowire core to exploit the carrier drift and tensile strain. These results demonstrate how bending in nano-heterostructures opens up new degrees of freedom for strain and device engineering.

1 Author R. B. Lewis , P. Corfdir , H. Küpers , T. Flissikowski , O. Brandt , L. Geelhaar

Nanowires bending over backward from strain partitioning in asymmetric core-shell heterostructures

Source Nano Lett. , 18 , 2343 ( 2018 )
DOI : 10.1021/acs.nanolett.7b05221 | 2989 Cite : Bibtex RIS
R. B. Lewis, P. Corfdir, H. Küpers, T. Flissikowski, O. Brandt, and L. Geelhaar