Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 11: Interfaces III

MM 11.4: Talk

Monday, March 26, 2007, 15:30–15:45, H6

Investigation of Fe/MgO interfaces by Atom Probe Tomography (APT) — •Alexander Mackel, Talaat Al-Kassab, and Reiner Kirchheim — Institut für Materialphysik, Friedrich-Hund-Platz 1, D-37077 Göttingen

Modern magnetic storage devices such as Magneto-resistive RAM (MRAM) devices are generally built up from a stack of thin layers, in which one of these layers is an oxide-barrier. The effect of Tunnelling Magneto-Resistance (TMR), governing the function of these devices, is strongly dependent on the electron transmission, in particular, at the Oxide/Metal interface. Therefore, it becomes important to characterize these interfaces on the nano-scale concerning their geometrical and chemical roughness. With this objective, we investigated the stacking of an ideal Fe/MgO/Fe sandwich type by means of APT.

The layers were prepared by ion beam sputtering on tungsten substrate-tips of 30 to 50nm radius of curvature as well as on Si-posts with a planar surface. Using a Focused Ion Beam, these posts were formed into a needle-like shaped tip to enable APT investigation.

The model system has been analyzed successfully for barrier thicknesses smaller than 2nm. So far, we found a FeO-peak in the time-of-flight mass spectrum of the interface indicating that Fe is partly oxidized already in the as-prepared state. The origin and presence of the FeO will be discussed as well as a comparison between the results obtained from both types of samples.

Financial support by the Deutsche Forschungsgemeinschaft, SFB602/B1 is gratefully acknowledged.