Strain relaxation by dislocation glide in ZnO/ZnMgO core-shell nanowires

TL;DR

This study investigates how dislocation glide relaxes strain in ZnO/ZnMgO core-shell nanowires, revealing mechanisms that enable plastic relaxation in both core and shell, which is crucial for device applications.

Contribution

It demonstrates that dislocation glide relaxes strain in both the core and shell of ZnO/ZnMgO nanowires, a novel insight for nanowire strain management.

Findings

Dislocation half-loops glide from free surfaces to relax strain.

Dislocations are observed within the nanowire core, unlike in 2D structures.

Both core and shell can undergo plastic relaxation.

Abstract

Plastic relaxation of the misfit stress in core-shell semi-conducting nanowires can lead to structural defects, detrimental to applications. Core-shell Zn{0.7}Mg{0.3}O/ZnO quantum well heterostructures were deposited on ZnO nanowires. Strain along the a and c axes of the wurtzite structure is relaxed through the glide of dislocation half-loops from the free surfaces, within pyramidal and prismatic planes. Some half-loops are closed up in the barriers to accommodate the misfit at two consecutive interfaces of the quantum well stack. Dislocations are also observed within the nanowire core: contrary to two-dimensional structures, both the core and the shell can be plastically relaxed.