Self-Assembled Nano Wires

We present a novel technique to fabricate self assembled nano wires on substrates, or channels of nano dimensions on thin films. The width of the wires or channels can be 50 nm and below, but their lengths can be 100s of micro meters. The technique is as follows: a substrate is coated by a film which is then strained either by applying load on the film-substrate system or by residual stress of the film itself. If the stress on the film exceeds that of its fracture stress, the film cracks with nano-dimensional opening to the substrate. The pattern of the cracks on the film depends on the type of stress (uniaxial or biaxial), strength of the interface between the substrate and the film, and the fracture strength of the film. Thus, the crack pattern can be controlled by tuning such parameters. The self assembled network of cracks can be used as nano channels, or the cracks can be filled by a metal that bonds with the substrate, which, after removal of the cracked film, gives a network of nano wires. We present the results of our initial experiments which have resulted Nickel wires on Si substrate. The wires are 300nm wide and millimeters long.