A scanning tunnelling microscope tip-induced migration of di-vacancies was observed on the (110) surface of n-doped material. Such motion occurred only for a negative polarity of the tunnelling voltage, and was directed along the [1¯10] direction; regardless of the scanning orientation. It was therefore purely non-thermal. It was suggested that a field-induced reduction of the barrier to migration initiated the motion. A quantitative analysis of the migration indicated the existence of long-lived excited states. This was consistent with charged trap states in doped semiconductors.

P.Ebert, M.G.Lagally, K.Urban: Physical Review Letters, 1993, 70[10], 1437-40