Pseudo-Superlattices of Bi_2Te_3 Topological Insulator Films with Enhanced Thermoelectric Performance

摘要

It was recently suggested theoretically that atomically thin films of Bi_2Te_3 topological insulators have strongly enhanced thermoelectric figure of merit. We used the "graphene-like" exfoliation process to obtain Bi_2Te_3 thin films. The films were stacked and subjected to thermal treatment to fabricate pseudo-superlattices of single crystal Bi_2Te_3 films. Thermal conductivity of these structures was measured by the "hot disk" and "laser flash" techniques. The room temperature in-plane and cross-plane thermal conductivity of the stacks decreased by a factor of～2.4 and 3.5 respectively as compared to that of bulk. The strong decrease of thermal conductivity with preserved electrical properties translates to ～140-250% increase in the thermoelectric figure if merit. It is expected that the film thinning to few-quintuples, and tuning of the Fermi level can lead to the topological insulator surface transport regime with the theoretically predicted extraordinary thermoelectric efficiency.