Mechanically-Exfoliated Stacks of Thin Films of Bismuth Telluride Topological Insulators with Enhanced Thermoelectric Performance

TL;DR

This paper demonstrates that mechanically exfoliated Bi2Te3 thin films form stacks with significantly reduced thermal conductivity, enhancing thermoelectric performance, and suggests tuning Fermi levels to reach topological-insulator surface transport for even better efficiency.

Contribution

It introduces a mechanical exfoliation method for Bi2Te3 films and shows how stacking reduces thermal conductivity while maintaining electrical properties, boosting thermoelectric performance.

Findings

Thermal conductivity decreases by up to 3.5 times in stacks.

Electrical properties are preserved despite reduced thermal conductivity.

Potential to achieve topological-insulator surface transport with optimized Fermi level.

Abstract

We report on "graphene-like" mechanical exfoliation of single-crystal Bi2Te3 films and thermoelectric characterization of the stacks of such films. Thermal conductivity of the resulting "pseudo-superlattices" was measured by the "hot disk" and "laser flash" techniques. The room-temperature in-plane (cross-plane) thermal conductivity of the stacks decreases by a factor of ~2.4 (3.5) as compared to bulk. The thermal conductivity reduction with preserved electrical properties leads to strong increase in the thermoelectric figure of merit. It is suggested that the film thinning to few-quintuples and tuning of the Fermi level can help in achieving the topological-insulator surface transport regime with an extraordinary thermoelectric efficiency.