Tapered BiTe nanowires synthesis by galvanic displacement reaction of compositionally modulated NiFe nanowires

Tapered BiTe nanowires with controlled periodicity and composition were synthesized by galvanic displacement reaction (GDR) of compositionally modulated NiFe nanowires. The Fe content in NiFe nanowires was controlled by sweeping the applied deposition potentials where more negative cathodic potential resulted in Fe-rich NiFe nanowires. Although the Bi/Te ratio at the shell of nanowires was uniform, the Bi/Te ratio altered from ∼0.7 to ∼1.5 as the Fe content of sacrificial NiFe increased from 22% to 78%. The periodicity with the BiTe nanowire was precisely controlled from 1.15 μm to 2.30 μm by adjusting the sweep rate from 2 mV/s to 0.5 mV/s. This work demonstrates the ability to create complex shaped semiconducting nanowires by engineering the sacrificial nanowires.