How low-temperature welding affects the nanostructure of nanowire junctions

Depending on the synthesis methods employed, nanowires for flexible electronics are either single crystals or possess a penta-twinned nanostructure. This nanostructure, along with the relative crystallographic orientation of the nanowires and the welding temperature, determines the degree of interpenetration between wires and the nanostructure of the junction. This study tracks, by means of atomistic simulations performed at various temperatures, the formation and evolution of the joint between pairs of nanowires. The results show that penta-twinned nanowires generally yield the greatest interpenetration between wires and the most significant nanostructural changes, driven by atomic diffusion facilitated by the presence of twin boundaries. In contrast, single-crystal nanowires can form, in specific orientations, nearly defect-free yet poorly interpenetrated junctions. While surface curvature is an important parameter that drives atomic diffusion and thus promotes interpenetration, it is the presence of twin boundaries that has a dominant role in triggering nanostructural variation in the nanowires during welding.