Surface atom migration-involved two-dimensional nucleation and growth of nanotwinned copper in DC electrodeposition

Direct-current (DC) Electrodeposited nanotwinned copper (nt-Cu) is a promising candidate for interconnection materials in integrated circuit for its excellent mechanical, electrical and thermal properties. However, the formation mechanism of nanotwins during DC electrodeposition of nt-Cu remains unclear. In this study, a two-dimensional nucleation and growth model of nt-Cu is established. The critical nucleation size and average twin spacing were evaluated theoretically. The results demonstrate a relatively high probability of twin nucleation through random stacking with the average twin spacing derived to be only ∼1 nm. The gap between theoretical and observed twinning probability can be ascribed to the surface migration-induced dissipation of nuclei. Molecular dynamics simulation further confirms the formation and subsequent dissipation of nuclei during deposition of Cu. By providing a clear illustration of nanotwin formation process, this study contributes to the understanding of nt-Cu electrodeposition.