In an examination of the chemical structures of the AlOx Co90 Fe10 interface, we confirmed that thermal treatment affects the redistribution of oxygen at the interface and that this leads to an increase in the tunneling barrier height of magnetic tunnel junctions. The as-deposited Al oxide barrier with a thickness of ~13 Å was oxygen-deficient AlOx, but most of it turned into Al2 O3, the thermodynamically stable stoichiometric phase, through annealing. This enrichment of oxygen is likely responsible for the observed improvement. The near-edge x-ray absorption fine structure spectra of Co and Fe proved the fact that after bonding with Co and Fe in the underlying CoFe layer, the oxygen diffused back into the barrier and thereby enriched the barrier to the point where it mostly consisted of Al2 O3. Our results confirm that controlling the chemical structures at the interface is a key to modify the properties of magnetic tunnel junctions.
Bibliographical noteFunding Information:
This work was supported by The National Research Program for the 0.1 Terabit Non-Volatile Memory Development sponsored by Korea Ministry of Science & Technology. Authors gratefully acknowledge T. J. Regan for fitting of XAS. Table I. Curve-fitted result for the Fe and Co L III -edge spectra of the as-deposited and annealed MTJs. Fe L III edge Co L III edge FeO α - Fe 2 O 3 CoO As-deposited Fraction (%) 34 66 100 MTJ Thickness (Å) 8.6 8.6 8.6 Annealed Fraction (%) 69 31 100 MTJ Thickness (Å) 4.6 4.6 2.1 FIG. 1. I ‐ V curves for (a) the as-deposited MTJ and (b) the annealed MTJ. FIG. 2. The curve-fitting analyses for the Al 2 p XPS spectra of (a) as-deposited film and (b) annealed film. FIG. 3. The curve-fitting analyses for Co L III -edge XAS of (a) as-deposited film and (b) annealed film. FIG. 4. The bilayer model for (a) Co and (b) Fe L -edge spectra of the as-deposited and annealed films. FIG. 5. The curve-fitting analyses for Fe L M -edge XAS of (a) as-deposited film and (b) annealed film.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)