Elastic vs. plastic strain relaxation in coalesced GaN nanowires: an x-ray diffraction study

TL;DR

This study investigates how GaN nanowires relax strain during coalescence, showing that plastic deformation via dislocation formation significantly reduces elastic bending energy, as confirmed by x-ray diffraction analysis.

Contribution

It provides a theoretical and experimental comparison of elastic and plastic strain relaxation mechanisms in coalesced GaN nanowires.

Findings

Dislocations at coalescence joints relax bending energy.

Plastic deformation reduces elastic strain in nanowires.

Residual bending causes extended diffraction profile tails.

Abstract

The coalescence in dense arrays of spontaneously formed GaN nanowires proceeds by bundling: adjacent nanowires bend and merge at their top, thus reducing their surface energy at the expense of the elastic energy of bending. We give a theoretical description of the energetics of this bundling process. The bending energy is shown to be substantially reduced by the creation of dislocations at the coalescence joints. A comparison of experimental and calculated x-ray diffraction profiles from ensembles of bundled nanowires demonstrates that a large part of the bending energy is indeed relaxed by plastic deformation. The residual bending manifests itself by extended tails of the diffraction profiles.