IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThP

Paper MI-ThP12
Formation of Barriers for Magnetic Tunneling: Ion Embedding vs Diffusion

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Magnetic Thin Films & Surfaces Poster Session
Presenter: S.O. Demokritov, University Kaiserslautern, Germany
Authors: S.O. Demokritov, University Kaiserslautern, Germany
B.F.P. Roos, University Kaiserslautern, Germany
P.A. Beck, University Kaiserslautern, Germany
B. Hillebrands, University Kaiserslautern, Germany
Correspondent: Click to Email
A novel type of oxidation technique, the ionized atom beam oxidation, was used to prepare ultrathin insulating aluminum oxide barriers for magnetic tunnel junctions. Thanks to high chemical reactivity of atomic oxygen combined with very low energy (30-50 eV) of the ions the oxide grows fast, homogeneous, and amorphous. The limited oxidation depth reduces the possibility of an overoxidation of the underlaying magnetic electrode. By means of in-situ techniques for monitoring the oxide growth during the oxidation, it was possible to identify two mechanisms which dominate the oxidation at different stages of the process. During the initial stage an ion embedding mechanism controls the oxidation. This mechanism describes the penetration of kinetic O-ions into the target metal layer until they are stopped on their way through the film by elastic and inelastic processes. The ions form chemical bindings with the surrounding metal atoms at their stopping place. The oxidation depth defined by this mechanism depends on the energy of the ions and reaches 1-2 nm. As the oxide layer grows, the incoming O-ions find less and less leftover metal atoms near their stopping place and a diffusion process starts to effect the oxidation. The further oxidation growth is determined by an electrical field controlled diffusion of metal and oxygen atoms. Monte-Carlo-simulations based on the developed "ion embedding with diffusion" model completely describe the formation of thin oxide barriers for magnetic tunnel junctions.