Synthesis and Characterization of One-Dimensional Cu-Sn Nanowire Diffusion Couples for Nanowire Assembly and Interconnection

In this work, we show that Cu-Sn based nanowires can be used as a one-dimensional (1-D) diffusion couple to study the atomic diffusion. In order to control the nano-soldering process and form reliable nano-joints (nanoscale interconnects between nanowires), fundamental study of wetting and intermetallic diffusion at the small dimension is necessary. An electrodeposition method is used to synthesize multisegmented nanowires in nanoporous templates in the diameter range of 15-200 nm and length up to 20 μm. By choosing two-segment Sn-Cu nanowires and symmetric three-segment Sn-Cu-Sn nanowires as the model systems in which Sn acts as the solder element and Cu serves as a functional element, we aim to understand the nanoscale soldering reaction along the one-dimension. The morphological evolutions of Sn and Cu segments and Kirkendall void formation in the Cu segment during the oven based soldering process have been observed. The fundamental principles of diffusion kinetics, primarily at a phenomenological level, are discussed. These studies and results provide important understanding in the design, assembly and integration of functional nanowires into nanoelectronics and nanodevices.