Innovative Growth Technique
To overcome this problem, a group led by Yasuhiro Kimura at the Nagoya University Graduate School of Engineering used atomic diffusion in a solid phase state enhanced by ion beam irradiation to create aluminum NWs from single crystals.

Atomic diffusion is a process by which atoms or molecules move from areas of high concentration to areas of low concentration, through stress state change under heat. Using ion beams, the crystal grains were irradiated inside the thin aluminum film to coarsen them at the surface layer. This caused changes in stress distribution, guiding atomic flow, and was used as a means of supplying mass atomic feedstocks for NW growth to specific locations. In practice, when heat was applied, there was an upward flow of atoms through the gradient from the fine grains on the bottom to the coarse ones on top, resulting in mass growth of NWs.