Dresden 2014 – scientific programme

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DS: Fachverband Dünne Schichten

DS 6: Thin Film Characterization: Structure Analysis and Composition (XRD, TEM, XPS, SIMS, RBS,...)

DS 6.5: Talk

Monday, March 31, 2014, 16:00–16:15, CHE 89

Epitaxial MgO/GaAs(001) studied by in-situ X-ray diffraction — •Thomas Hentschel, Michael Hanke, Oliver Bierwagen, Andre Proessdorf, and Jens Herfort — Paul-Drude-Institut Berlin, Hausvogteiplatz 5-7, 10117 Berlin, Germany

The integration of Magnesiumoxide MgO into magnetic tunnel junctions or ferromagnet/semiconductur-hybrid structures acting as a potential tunnel and diffusion barrier has drawn much attention in the last years. Although the growth of MgO by different procedures is well established and used in various applications, its structural properties and growth mechanisms apparently have not been of much interest yet.

This contribution presents in-situ X-ray diffraction measurements carried out during molecular beam epitaxy of 5 to 30 nm thick MgO films on GaAs(001). All samples were grown at a substrate temperature of T_S=350 ^∘C by evaporating metallic Mg from an effusion cell with a sapphire crucible and providing additional molecular oxygen at a partial pressure of 10⁻⁶ mbar. It is observed that the in-plane orientation of MgO depends on the growth rate, while the ouf-of-plane orientation remains unchanged with MgO_[001]||GaAs_[001]. For a growth rate of 1 Å/min the cubic rocksalt structure-like MgO with a misfit of about 25% to GaAs grows directly cube-on-cube on top of the substrate with an in-plane orientation of MgO_[110]||GaAs_[110]. If the growth rate is increased by a factor of 4 the in-plane orientation rotates by 45^∘. The resulting orientation is MgO_[100]||GaAs_[110]. We attribute this in-plane rotation to unoxidized Mg clusters formed at the GaAs interface.