Designing Diameter-Modulated Heterostructure Nanowires of PbTe/Te by Controlled Dewetting

Heterostructures
consisting of semiconductors with controlled morphology
and interfaces find applications in many fields. A range of axial,
radial, and diameter-modulated nanostructures have been synthesized
primarily using vapor phase methods. Here, we present a simple wet
chemical routine to synthesize heterostructures of PbTe/Te using Te
nanowires as templates. A morphology evolution study for the formation
of these heterostructures has been performed. On the basis of these
control experiments, a pathway for the formation of these nanostructures
is proposed. Reduction of a Pb precursor to Pb on Te nanowire templates
followed by interdiffusion of Pb/Te leads to the formation of a thin
shell of PbTe on the Te wires. Controlled dewetting of the thin shell
leads to the formation of cube-shaped PbTe that is periodically arranged
on the Te wires. Using control experiments, we show that different
reactions parameters like rate of addition of the reducing agent,
concentration of Pb precursor and thickness of initial Te nanowire
play a critical role in controlling the spacing between the PbTe cubes
on the Te wires. Using simple surface energy arguments, we propose
a mechanism for the formation of the hybrid. The principles presented
are general and can be exploited for the synthesis of other nanoscale
heterostructures.