First-Principles Study on Lattice Structures and Bonding Character of CoSb3/Ti Interface

Interfacial structure plays a critical role in the application of thermoelectric (TE) devices. To understand the bonding character of the CoSb3/Ti interface, we investigated its lattice structure, interface bonding energy, and electronic properties by first-principles calculations. Six possible models for CoSb3/Ti interfaces with an orientation relationship of [1 0 0](0 0 1)(CoSb3)//[2 0](0 1 0)(Ti) were considered. The atomic positions and bond lengths changed obviously on the interface after relaxation. Through calculations of adhesion energies of all the candidate interfaces, it was found that one-layer Sb-terminated CoSb3(0 0 1)/Ti(0 1 0) interface has the largest bonding energy. This indicates that the one-layer Sb-terminated interface is the most stable configuration. It was found that electrons are largely redistributed on the interface according to our analysis on partial density of states and interface difference charge density. The electrons of atoms near interface transfer toward the gap between the interfacial Ti and CoSb3 layer. Both electron transfer and orbital hybridization promote bonding between atoms and the interfacial bonds are mainly metallic. Little covalent bonding is involved at the interface as well.