The microstructure and mechanical properties of twinned copper-bismuth films obtained by DC electrodeposition

Abstract

The engineering of grain boundaries (GB) by controlled twin boundaries introduction in the copper matrix is a promising way to achieve higher strength coupled with sufficient ductility and conductivity of copper materials being in a high demand for modern electronics. In the work, the oversized Bi atoms were introduced in the copper film using two step direct current (DC) electrodeposition technique. Via XRD, SEM and EBSD techniques it was shown that the fraction of twinned boundaries and the orientation of Cu and (100-x)Cu-xBi (x = 0.1, 0.5, 0.75 mol.%) films highly depend on the Bi(NiO3)3 concentration in the bath solution. Copper films possess both remarkably high hardness of 1.9 ± 0.2 GPa and Elastic modulus of 67 ± 7 GPa The 99.5Cu-0.5Bi (mol.%) film possesses the moderate hardness of 1 ± 0.1 GPa and Elastic modulus of 94 ± 9 GPa. Possible mechanisms of bismuth incorporation in the structure and its effect on mechanical properties of the copper based films are discussed.