Formation and characterization of Ni_xlnAs/lnAs nanowire heterostructures by solid source reaction

The formation of crystalline Ni_xnAs and Ni_xlnAs/InAs/ Ni_xlnAs heterostructure nanowires by the solid source reaction of InAs nanowires with Ni is reported for the first time. The fundamental kinetics of the Ni/lnAs alloying reaction is explored, with the Ni diffusion reported as the rate determining step. The diffusivity of Ni is independent of the nanowire diameter, with an extracted diffusion activation energy of ∼1 eV/atom. The metallic Ni_xlnAs exhibits a modest resistivity of ∼167 μΩ.cm for diameters >30 nm, with the resistivity increasing as the nanowire diameter is further reduced due to the enhanced surface scattering. The alloying reaction readily enables the fabrication of Ni_xInAs/InAs/ Ni_xlnAs heterostructure nanowire transistors for which the length of the InAs segment (i.e., channel length) is controllably reduced through subsequent thermal annealing steps, therefore enabling a systematic study of electrical properties as a function of channel length. From the electrical transport studies, an electron mean free path on the order of a few hundred nm is observed for InAs NWs with a unit length normalized, ON-state resistance of ∼7.5 kΩ/μm. This approach presents a route toward the fabrication for high performance InAs nanowire transistors with ohmic nanoscale contacts and low parasitic capacitances and resistances. © 2008 American Chemical Society.