Low temperature melting of copper nanorod arrays

We report the melting of nanorod arrays of copper at temperatures much lower than its bulk melting point (1083 degrees C). The Cu nanorods were produced by an oblique angle sputter deposition technique through a physical self-assembly mechanism due to the shadowing effect. The as-deposited nanorods were similar to 2300 nm in length, similar to 100 nm in diameter, and separated from each other with gaps varying between similar to 10 and similar to 30 nm. The melting process was investigated through the analysis of scanning electron microscopy, transmission electron microscopy, and x-ray diffraction measurements. Start of premelting (or surface melting) has been observed to occur at annealing temperature similar to 400 degrees C under vacuum (10(-6) Torr). As the temperature was raised the arrays of Cu nanorods started to coalesce and formed a dense continuous film with a (111) texture at similar to 550 degrees C. The results of this work may be useful for low temperature soldering applications.