2, Manhattan College, Riverdale, New York, United States
3, Sandia National Laboratories, Albuquerque, New Mexico, United States
4, Sandia National Laboratories, Albuquerque, New Mexico, United States
It is of particular interest to understand the factors that dominates the interface diffusion of metallic contacts on thermoelectric power devices during operation due to the loss of heat-to-electric power conversion efficiency. Au is the metal of choice due to its chemical inertness and high electrical and thermal conductivities. However, Au slowly diffuses into the van der Waals gaps of BiSbTe at operating temperatures degrading the efficiency, which is undesirable for medium to long-term applications. Intermetallic barriers such as nickel and cobalt are currently employed to prevent Au diffusion, but Au is still permeable resulting in a larger contact resistance and a minimal loss of material. Furthermore, the thermoelectric characteristics of such systems have not been reported yet. In this work, a GeNi alloy barrier is explored. We found that GeNi barrier does not alter the electrical conductivity even after long-term studies. EDS studies showed that GeNi effectively stop Au diffusion into the thermoelectric material. BiSbTe nanowire (NW) studies are also presented. In our work, we measured the thermoelectric properties of BiSbTe NW from 25 K to 310 K with Ge/Ni/Au contact and Ni/Au, Au contacts for comparison. The properties of BiSbTe NW remain the same after long thermal aging (8 h annealing at 250 in forming gas) while with only Ni as barrier or without barrier, the electrical conductivity and Seebeck coefficient both degraded. The formation of GeTe barriers the metal diffusion. Ni forms an Ohmic contact with BiSbTe and prevents the eutectic formation of GeAu.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.