Reduction of contact resistance at terminations of bismuth wire arrays

Contact resistance at the terminations of bismuth wire arrays of 25-μm diam is reduced by ion plating of a titanium interlayer 100nm upon the wire ends. One-thousand (1000)-nm-thick copper electrodes are ion plated upon the titanium. Copper probe electrodes are then attached using Pb-Sn solder. The temperature dependences of the Seebeck coefficient and resistance are measured upon heating from 25to300K and the results compared with those for the polycrystalline bulk bismuth sample. The resistivity of the microwire array is found to be 1.37μΩm at 300K. Based on the similarities between the temperature dependences of resistivity and Seebeck coefficient for the wire and bulk samples, contact resistance of the wires is considered to have been completely eliminated. This technique makes it possible to simultaneously estimate the resistivity and Seebeck coefficient for nanowire arrays of thermoelectric materials.