Weakening of the Cu/Cu3Sn(100) Interface by Bi Impurities

Abstract

We have performed density functional theory calculations to examine the role of Bi impurities in modifying the structure and properties of the Cu/Cu(3)Sn(100) interface. Analysis of the heat of supercell formation reveals that Bi atoms preferentially replace Cu atom in the Cu slab. Substitution of Cu by Bi reduces the adhesion energy of the interface from 1.5 J/m(2) to 1.1 J/m(2), primarily due to the atomic size effect. The size effect leads to expansion of the interface, because surrounding Cu and Sn atoms are pushed away from the misfit Bi atoms. Analysis of electronic density indicates that the local charge density is dispersed around Bi atoms. The presence of a Bi atom makes surrounding atoms less active, which is attributed to the reduction of hybridizations.