The electromigration-induced dynamics of surface dislocations in flame-annealed films were studied by using scanning tunnelling microscopy. The emergence of new dislocations appeared to be strongly correlated with the onset of current stressing, and their direction was correlated with that of the current. The emergence rate decreased with the elapsed time since flame-annealing. The temporal evolution of the dislocations was usually more stable under electromigration than were normal atomic steps. The fact that dislocation emergence created such stable surface structures was considered to be important in itself. The results also indicated that the current onset played such a special role in the formation of dislocations perhaps because of the associated current and voltage spikes. No new dislocations appeared during (slow) current turn-off. Most of the current-induced surface dislocations ran in the <110> direction that was closest to that of the current flow; with no observable dependence upon the direction of pre-existing dislocations. It was not clear whether bulk dislocations migrated to the surface, or whether the dislocations were formed by current-triggered relaxation of strains within a few atomic sub-surface layers. No correlation between the density of pre-existing dislocations and the formation rate of new dislocations was found over a large density range.

Electromigration Induced Dynamics of Surface Dislocations and Atomic Steps. N.Shimoni, O.Biham, O.Millo: Journal of Vacuum Science and Technology A, 1999, 17[4], 1693-6