Bending of core-shell nanowires by asymmetric shell depositionFreestanding semiconductor nanowires have opened up new possibilities for
semiconductor devices, enabling geometries, material combinations and strain
states which were not previously possible. Along these lines, spontaneous
bending in asymmetric core-shell nanowire heterostructures has recently been
proposed as a means to realize previously unimagined device geometries, novel
strain-gradient engineering and bottom-up device fabrication. The synthesis of
these nanostructures exploits the nanowire geometry and the directionality of
the shell deposition process. Here, we explore the underlying mechanisms of
this bending process by modeling the evolution of nanowires during asymmetric
shell deposition. We show how bending can lead to dramatic local shell
thickness, curvature and strain variations along the length of the nanowire,
and we elucidate the dependence of shell growth and bending on parameters such
as the core and shell dimensions and materials, and angle of incidence of the
deposition source. In addition, deposition shadowing by neighboring nanowires
is explored. We show that shadowing can easily be employed to connect nanowire
pairs, which could be used to fabricate novel nanowire sensors. Model results
are compared with GaAs-InP and GaAs-(Al,In)As core-shell nanowire growth
experiments. These results can be used to guide future experiments and to help
pave the way to bent nanowire devices.
arxiv.org