Unveiling orientation-driven asymmetrical mechanical properties and deformation mechanisms in wurtzite GaN nanowires

JMR Dhrubo and ASMJ Islam and MS Islam and J Park, PHYSICA SCRIPTA, 100, 075941 (2025).

DOI: 10.1088/1402-4896/ade1b7

Controlling the mechanical properties of wurtzite (WZ) GaN nanowires (NWs) is particularly important for their applications in nanoelectronics and nanoelectromechanical systems. However, an in-depth understanding of the mechanical properties and deformation mechanisms of GaN NWs is still missing because of the variety of shapes and crystal orientations in fabricated NWs. This work employs molecular dynamics simulations with Stillinger-Weber potentials to reveal the crucial roles of shape and crystal orientations in the tensile mechanical behavior and deformation processes of WZ GaN NWs. While there are changes in the shape of NWs from triangular to hexagonal, NWs with dominant surface facets exhibit distinct mechanical properties due to the activation of distinct inelastic deformation mechanisms. Moreover, due to the change in strain rate and temperature, there is an activation variation in different planes and the production of dissimilar interplanar distances, which further affect the strain rate sensitivity and produce slipping and/or twinning mechanisms responsible for the anisotropic mechanical behavior of WZ GaN NWs. Although all the NWs fail in a brittle manner without necking at low strain rates, necking phenomena are observed at higher strain rates. The <0001>-directed hexagonal shape NWs with 11 2 0 side facets show the highest fracture strength, elastic modulus, and fracture toughness, while the <1 1 00>-directed triangular shape NWs with 0001, 11 22 and 11 2 2 side facets show the lowest values. We find that failure in triangular-shaped NWs is due to deformation phenomena such as slipping along the 01 1 0 and 1 1 00 planes. On the other hand, failure in hexagonal-shaped NWs results from cleavage in the 0001 plane. Our research offers significant insights into regulating the mechanical properties of GaN NWs, thereby enhancing their effectiveness in nanoscale devices and systems.

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