Thermodynamic Stability of Ni/Sb2Te3 Interface by First-Principles Calculations

Solid-state thermoelectric devices have been attrac ting considerable attention for the applications of cool er and power generation. The high-performance crystalline Sb2Te3 and its solid solution with Bi substitution, (Sb xBi1x)2Te3, to enhance thermoelectric properties of ZT (=STσ/κ) has been proposed and demonstrated [1,2], where S is Seebeck coefficient, σ is electrical conductivity and κ is thermal conductivity. A low-cost Ni has been utilized as a diffusion barrier between Cu and thermoelectric elements. However, a pending issue r elated to poor thermo-stability on thermoelectric material still remains unsolved. To address this issue, we made a systematic comparison of calculating interface form ation energy for Ni/Sb2Te3 samples with different terminated surfaces to discover the energetic favorable interf ac configurations. To clarify the interface stability at Ni/Sb2Te3 interfaces, the Sband Te-terminated Sb 2Te3 in direct contact with Ni barrier was computed by rela xing 2x2x1 supercell with constrained Sb 2Te3, where unit cell was defined to contain six Sb and nine Te atoms as shown in Figure 1. The interfaces were modeled by a super lattice including one interface and a 17 Å vacuum layer on top. Subsequently, the first principles calculations usi ng the total energy plane-wave basis code VASP [3] were performed to investigate the impact of various configurations of Sb and Te termination. In equation 1, the interface formation energies as a function of tellurium chemical potentials can be de fin d as [4]: