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

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

T.E. Huber¹, A. Nikolaeva², A. Gitsu², D. Konopko², M.J. Graf³

^{1 Howard University, Washington, DC 20059, USA
^{2 Institute of Solid State Physics, Academy of Sciences, Moldova
^{3 Department of Physics, Boston College, Chestmut Hill, MA, USA.}}}

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.