Thermoelectric materials have exciting low-temperature applications in waste recovery and refrigeration. One of the most promising thermoelectric materials to date is a superlattice of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3). These heterostructures have reportedly exhibited thermoelectric efficiencies at room temperature that are more than twice that of industrial thermoelectrics. The purpose of this thesis is to grow these superlattices by molecular beam epitaxy and independently verify these claims. We begin by developing a growth protocol to grow films on a thickness scale that would allow for the measurement of thermal transport through the film. A comprehensive characterization procedure for each sample was paramount to improving the quality of these films. By characterizing the samples with x-ray diffraction, x-ray reflectivity, and transmission electron microscopy, we demonstrate the growth of superlattices with well-defined interfaces and superlattice period.
After growth and characterization, we perform electrical and thermal transport measurements on the samples. We use the standard Hall bar geometry for electrical transport to determine resistivity, carrier concentration, and carrier mobility as a function of temperature. In addition, we also characterize the transport through topological surface states in these films. For thermal measurements, we implemented the 3ω method for measuring the thermal conductivity of electrically conducting films.
