Influence of interfacial structure on bonding strength and thermoelectric transport properties of Cu6Sn5/Cu interface

Abstract

The bonding strength, electrical conductivity and thermal conductivity of Cu6Sn5/Cu interface with different interfacial structures, including Cu6Sn5 (001)/Cu (110) interface, Cu6Sn5 (110)/Cu (001) interface and Cu6Sn5 (110)/Cu (111) interface, were investigated by using density functional theory and semi-classical Boltzmann transport theory. The results indicate that, the chemical bonds were generated on the three interfaces, and maximum charge densities of Cu6Sn5 (001)/Cu (110) interface, Cu6Sn5 (110)/Cu (001) interface and Cu6Sn5 (110)/Cu (111) interface are 1.24 e/Å3, 2.51 e/Å3 and 2.43 e/Å3, respectively. This result leads that the bonding strength, electrical conductivity and thermal conductivity of Cu6Sn5 (001)/Cu (110) interface are all lower than the other two interfaces. Moreover, the interfacial chemical bonds exhibit ionic characteristic and covalence characteristic simultaneously. Both ionic characteristic and covalence characteristic of Cu6Sn5 (110)/Cu (001) interface are stronger than Cu6Sn5 (110)/Cu (111) interface. Therefore, although the charge densities on Cu6Sn5 (110)/Cu (001) interface and Cu6Sn5 (110)/Cu (111) interface are similar, the electron localization of Cu6Sn5 (110)/Cu (001) interface is much stronger, leading to the smaller number of free electrons. Therefore, the result that electrical conductivity and thermal conductivity of Cu6Sn5 (110)/Cu (001) interface are 1.48 times and 1.56 times those of Cu6Sn5 (110)/Cu (111) interface was achieved.