Improving the morphological stability of a polycrystalline tungsten nanowire with a carbon shell.

Polycrystalline tungsten nanowire is studied for its potential as an interconnect for nanodevices. At elevated temperatures arising from Joule heating at high current densities, a bare 40 nm nanowire was observed in situ in a transmission electron microscope to undergo grain grooving that eventually led to its breakage. By overcoating a carbonaceous layer onto the nanowire surface, the tungsten-carbon core-shell structure was found to sustain a much higher current density of about 3 x 10(7) A cm( - 2) before failure, despite significantly higher peak temperature as a result of Joule heating. Failure occurred as a result of a different form of morphological transformation leading finally to breakage by electromigration. These findings suggest that the metal-carbon core-shell structure provides a solution to circumvent morphological instability and increase the current-carrying capability of metallic polycrystalline nanowires.