Thermoelectric power of Bi and Bi(1-x)Te(x), x=0.0014,in porous Vycor glass

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Semiconductor quantum wires constitute a promising thermoelectric material because of the increase of the electronic density of states in low-dimensional materials. We studied the magnetic-field-dependent resistance and Seebeck coefficient of a high-density network of 6-nm-diameter wires of Bi and of Bi(1-x)Te(x), x=0.0014, in porous Vycor glass. The resistance R increases as temperature decreases from 300 K down to 0.3 K for both composites. However, in contrast to recent results that demonstrate the semiconducting behavior of the resistance and very large enhancements of the thermoelectric power of composites containing Bi nanowires with diameters of 9 and 15 nm, we find that the resistance is not thermally activated and that the thermoelectric power of the composites is of the same order of magnitude as the thermoelectric power of bulk Bi. Our results are consistent with the nanowires having carrier density that is enhanced by surface effects.