Pseudo-Superlattices of Bi₂Te₃ Topological Insulator Films with Enhanced Thermoelectric Performance

Abstract

It was recently suggested theoretically that atomically thin films of Bi₂Te₃ topological insulators have strongly enhanced thermoelectric figure of merit. We used the “graphene-like” exfoliation process to obtain Bi₂Te₃ thin films. The films were stacked and subjected to thermal treatment to fabricate pseudo-superlattices of single crystal Bi₂Te₃ 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.