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
1Howard University, Washington, DC 20059, USA
2Institute of Solid State Physics, Academy of Sciences, Moldova
3Department 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 Heremansí results, we find that the compositesís 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.