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DS: Dünne Schichten

DS 2: Elektrische und optische Eigenschaften II

DS 2.3: Talk

Monday, March 11, 2002, 11:30–11:45, HS 31

Dielectric breakdown in AlO_x films on Co studied with a scanning tunneling microscope — •S. Czerkas, M. Justus, K. Rott, A. Thomas, H. Brückl, and G. Reiss — Universität Bielefeld, Fakultät für Physik, Universitätsstr.25, 33615 Bielefeld

Magnetic tunnel junctions consist of ferromagnetic electrodes separated by a thin oxide barrier. The properties of this insulating barrier are crucial for a proper operation of a junction. The main goal of our study was to induce locally a dielectric breakdown of aluminium oxide films grown on a ferromagnet (cobalt) and subsequently investigate the breakdown site with STM.

In an UHV system 10 nm Co and 0.3...1 nm Al were deposited onto a SiO₂ substrate. Al was then oxidized in O₂ atmosphere. A breakdown in the aluminium oxide film was forced by increasing the STM bias voltage under constant current feedback and indicated by a sudden distance change of the tip from the surface, i.e. the electrical
conductivity increases on top of the breakdown site. The onset of the breakdown voltage is about 3 V. The breakdown feature has a diameter of about 40 nm.