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 °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 ∼2300 nm in length, ∼100 nm in diameter, and separated from each other with gaps varying between ∼10 and ∼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 ∼400 °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 ∼550 °C. The results of this work may be useful for low temperature soldering applications. [ABSTRACT FROM AUTHOR]