Reduction of contact resistance at terminations of bismuth wire arrays

Contact resistance at the terminations of bismuth wire array of 25 mum diameter is reduced by ion plating of a titanium interlayer 100 nm upon the wire ends. 1,000 nm-thick copper electrodes are ion plated upon the titanium. Copper probe electrodes are then attached using Pb-Sn solder. The temperature dependence of the Seebeck coefficient and resistance are measured upon heating from 25 K to 300 K and the results compared with those for the polycrystalline bulk bismuth sample. The resistivity of the micro-wire array is found to be 1.37 muOmega m at 300 K. 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 nano-wire arrays of thermoelectric materials