Atomically Thin Films of Bismuth Telluride: ``Graphene-Like'' Exfoliation and Thermoelectric Applications

It follows from theoretical predictions that a drastic improvement in ZT can be achieved in low-dimensional structures where electrons and phonons are strongly confined in one or two dimensions. The latter would require carrier confinement in a quantum well with a width on the order of $\sim $1 nm and very high potential barriers. Conventional materials growth techniques are not capable of producing such crystalline structures. In this talk, we show that separate Bi-Te atomic layers can be mechanically exfoliated from bulk bismuth telluride crystal following a procedure similar to the exfoliation of graphene. The presence of the van der Waals bonds between five-fold layers allowed us to disassemble bismuth telluride crystals into films with the thickness of five atomic layers and less [1]. The resulting quasi-2-D crystals retain their good electrical conduction and poor thermal conduction properties important for thermoelectric applications. [1] Supplemental Info at: \underline {http://ndl.ee.ucr.edu}