Investigation of the interdiffusion of Sb and Bi in [Bi/sub 2/Te/sub 3/]/sub x/{Sb/sub 2/Te/sub 3/]/sub y/ superlattices

[Bi2Te3]x[Sb2Te3]y superlattices have been shown to have decreased thermal conductivities as compared to bulk alloys, resulting in enhanced thermoelectric efficiency. A key to the preparation of these kinetically stable superlattices has been the use of low temperature epitaxial growth techniques. We are exploring the use of modulated elemental reactants to synthesize [Bi2Te3]x[Sb2Te3]y superlattices by controlling the diffusion distance through modulated layers of the elemental reactants. The modulated elemental reactants are made by depositing thin alternating layers of Bi and Te followed by alternating thin layers of Sb and Te onto ambient substrates to yield a series of superlattice precursors with varying periods. X-ray reflectivity, x-ray diffraction and Time of FlightSecondary Ion Mass Spectrometry have been used to characterize the superlattice precursors and their evolution as a function of temperature. For various x and y formation of the desired superlattice competes with interdiffusion of the Bi2Te3 and Sb2Te3 layers at elevated temperatures. This competition has been explored as a function of annealing temperature and time and will be discussed.