Thermoelectric power of a network of 6-nm Bi nanowires in a porous Vycor glass matrix

T.E. Huber^{1}, A. Nikolaeva^{2}, A. Gitsu^{2}, D. Konopko^{2}, M.J. Graf^{3}

Semiconductor quantum wires constitute a promising thermoelectric material because of the increase of the electronic density of states in low dimensional materials. Recently, Heremans *et al* (Phys. Rev. Lett. __88__ , 216801 (2002)) and reported semiconducting behaviour of the resistance and very large enhancements of the thermoelectric power of composites containing Bi nanowires with diameters of 9 nm and 15 nm embedded in silica and alumina matrices. We studied the magnetic field dependent resistance and Seebeck coefficient of a high density network of 6 nm diameter wires of Bi and Bi doped with 0.14 at.% of Te embedded in monolithic porous silica in order to observe the expected properties. R increases weakly for both composites. However, in contrast to Heremans’ results, we find that the composites’s thermoelectric power is metallic (> 0) and of the order of magnitude of the thermoelectric power of bulk Bi. Our results are interpreted in terms of a model of surface charges that spoil the semimetal-to-semiconductor transition of quantum wires.