Multiple Twinning and Stacking Faults in Silver Dendrites

Abstract

Detailed defect structure of dendrite formation was studied in order to connect the mesoscopic with the atomistic structure. It was demonstrated that twinning and stacking fault formation play a central role in the growth of electrodeposited Ag dendrites. The broad faces of Ag dendrites and the main trunk growth direction were found to be (1̅11) and [1̅12̅], respectively. Dendrite branches also formed and grew from the main trunk parallel to the [121̅] and [2̅1̅1̅] crystallographic directions. Twins and stacking faults were found to reside on the {111} crystallographic planes, as expected for a face centered cubic (FCC) Ag crystal. Using electron back scattered diffraction (EBSD) we found two variants of in-plane 60° rotational twin domains in the (1̅11) broad dendrite surface plane. The intersections of twins and stacking faults with dendrite arm surfaces are perpendicular to the ⟨112⟩ arm growth directions. However, occasionally twins on the {111} planes parallel to the ⟨112⟩ arm growth directions were also observed. Although defect assisted dendrite growth is facilitated by twinning and stacking fault formation on {111} planes, the growth directions of the trunk and branches are not of the ⟨111⟩ type, but rather close to ⟨112⟩. The ⟨112⟩ growth directions are maintained by breaking dendrite facets into thermodynamically stable 111 and 200 steps and structural ledges of different length.