It was noted that recent time-resolved scanning tunneling microscopic studies of the modification of the (111) 7 x 7 surface at the atomic scale had revealed the role which was played by field-assisted diffusion in this process. A summary was made here of the experimental evidence for field-assisted diffusion in terms of a simple qualitative model which involved both direct pulse-induced field evaporation of material between the tip and sample, as well as field activation of atoms near to the tunnel junction, followed by field-assisted diffusion into the tunnelling region. These resulted in changes that occurred up to 600ms after the application of a voltage pulse. It was concluded that the control of such diffusion processes was essential in order to achieve reproducible atomic-scale fabrication. The results suggested that reduction of the applied field after the pulse was one means of eliminating unwanted diffusion events.

D.Huang, F.Grey, M.Aono: Japanese Journal of Applied Physics, 1995, 34[I-6B], 3373-5