In-situ X-ray analysis of misfit strain and curvature of bent polytypic GaAs-In(x)Ga(1-x)As core-shell nanowires

TL;DR

This study uses in-situ X-ray diffraction to analyze how asymmetric shell growth causes bending and strain release in GaAs-InGaAs core-shell nanowires, revealing substrate-dependent bending behavior.

Contribution

It provides the first in-situ X-ray analysis of strain and curvature evolution during asymmetric shell growth in bent nanowires.

Findings

Bending direction depends on substrate oxide type.

Strain develops and relaxes during shell deposition.

Bending correlates with in-situ X-ray diffraction data.

Abstract

Misfit strain in core-shell nanowires can be elastically released by nanowire bending in case of asymmetric shell growth around the nanowire core. In this work, we investigate the bending of GaAs nanowires during the asymmetric overgrowth by an In(x)Ga(1-x)As shell caused by avoiding substrate rotation. We observe that the nanowire bending direction depends on the nature of the substrate's oxide layer, demonstrated by Si substrates covered by native and thermal oxide layers. Further, we follow the bending evolution by time-resolved in-situ X-ray diffraction measurements during the deposition of the asymmetric shell. The XRD measurements give insight into the temporal development of the strain as well as the bending evolution in the core-shell nanowire.