Dynamics and control of gold-encapped gallium arsenide nanowires imaged by 4D electron microscopy

TL;DR

This study uses 4D electron microscopy to directly image and control the phase reaction dynamics of gold-encapped gallium arsenide nanowires, revealing transient states and thermodynamic parameters with high spatial and temporal resolution.

Contribution

It introduces a non-destructive method for real-time imaging and control of phase reactions in nanowires, advancing understanding of alloy formation at the nanoscale.

Findings

Visualization of nucleation, growth, and solidification processes

Determination of thermodynamic parameters of alloy phases

Observation of phase reaction at lower temperatures than melting points

Abstract

Eutectic related reaction is a special chemical/physical reaction involving multiple phases, solid and liquid. Visualization of phase reaction of composite nanomaterials with high spatial and temporal resolution provides a key understanding of alloy growth with important industrial applications. However, it has been a rather challenging task. Here we report the direct imaging and control of the phase reaction dynamics of a single, as-grown free-standing gallium arsenide nanowire encapped with a gold nanoparticle, free from environmental confinement or disturbance, using four-dimensional electron microscopy. The non-destructive preparation of as-grown free-standing nanowires without supporting films allows us to study their anisotropic properties in their native environment with better statistical character. A laser heating pulse initiates the eutectic related reaction at a temperature much lower than the melting points of the composite materials, followed by a precisely time-delayed electron pulse to visualize the irreversible transient states of nucleation, growth and solidification of the complex. Combined with theoretical modeling, useful thermodynamic parameters of the newly formed alloy phases and their crystal structures could be determined. This technique of dynamical control and 4D imaging of phase reaction processes on the nanometer-ultrafast time scale open new venues for engineering various reactions in a wide variety of other systems.