STM-induced reversible switching of local conductivity in thin Al2O3 films- art. no. 153407

The local electron transport properties of thin aluminum oxide layers used for magnetic tunnel junctions were studied in situ by scanning tunneling mi croscopy (STM) and spectroscopy under ultrahigh-vacuum conditions. The STM images of the oxide films reveal a granular structure, down to atomic resol ution. A reversible switching of the conductive properties of grains, attri buted to a charge redistribution, is observed during scanning. We demonstra te the possibility of intentionally switching a grain to the low-resistance state by exposing it to a high current density. We conjecture that the obs erved switching behavior may be considered as the precursor of an electric breakdown in tunnel junctions.