In Situ Heat-Induced Replacement of GaAs Nanowires by Au

Here
we report on the heat-induced solid-state replacement of GaAs by Au
in nanowires. Such replacement of semiconductor nanowires by metals
is envisioned as a method to achieve well-defined junctions within
nanowires. To better understand the mechanisms and dynamics that govern
the replacement reaction, we performed in situ heating studies using
high-resolution scanning transmission electron microscopy. The dynamic
evolution of the phase boundary was investigated, as well as the crystal
structure and orientation of the different phases at reaction temperatures.
In general, the replacement proceeds one GaAs(111) bilayer at a time,
and no fixed epitaxial relation could be found between the two phases.
The relative orientation of the phases affects the replacement dynamics
and can induce growth twins in the Au nanowire phase. In the case
of a limited Au supply, the metal phase can also become liquid.