  Bismuth telluride (Bi2Te3) and its alloys are the best bulk thermoelectric
materials known today. The stacked quasi-two-dimensional (2D) layers of Bi2Te3
were also identified as topological insulators. In this paper we describe a
method for graphene-inspired exfoliation of crystalline bismuth telluride films
with a thickness of a few atoms. The atomically thin films were suspended
across trenches in Si/SiO2 substrates, and subjected to detail
characterization. The presence of the van der Waals gaps allowed us to
disassemble Bi2Te3 crystal into its quintuple building blocks - five
mono-atomic sheets consisting of Te(1)-Bi-Te(2)-Bi-Te(1). By altering the
thickness and sequence of atomic planes we were able to create designer
non-stoichiometric quasi-2D crystalline films, change their composition and
doping, as well as other properties. The exfoliated quintuples and ultra-thin
films have low thermal conductivity, high electrical conductivity and enhanced
thermoelectric properties. The obtained results pave the way for producing
stacks of crystalline bismuth telluride quantum wells with the strong spatial
confinement of charge carriers and acoustic phonons for thermoelectric devices.
The developed technology for producing free-standing quasi-2D layers of
Te(1)-Bi-Te(2)-Bi-Te(1) creates an impetus for investigation of the topological
insulators and their possible practical applications.
