Growth of metal and metal oxide nanowires driven by the stress-induced migration

High quality Al and CuO nanowries are fabricated by simply heating the Al and Cu samples in air. Although the experimental operations and the stress-induced migration processes are quite similar, the causes of the driving forces and the growth mechanism are completely different. For the growth of Al nanowires, the driving force is determined to be the compressive stresses caused by the thermal expansion mismatch between Al film and Si substrate, and the growth mechanism is proposed to be the extrusion of atoms from the bases of nanowires (EAFB). For the growth of CuO nanowires, the driving force is determined to be the compressive stresses caused by the formation of Cu oxide layers, and the growth mechanism is proposed to be the formation of oxide molecules on surfaces of the nanowires (FOOS). The direct experimental observations of both EAFB and FOOS are presented. It is also demonstrated that stress distribution on the macroscopic level, which is caused by thermal or mechanical manipulation, can also influence the growth of CuO nanowires, which makes it prospective to control the growth of metal oxide nanowires by designing the stress distribution within the sample from which the nanowires are generated.