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MM: Fachverband Metall- und Materialphysik

MM 41: Interfaces II

MM 41.5: Vortrag

Donnerstag, 26. März 2009, 12:45–13:00, IFW D

Interface width of immiscible layered elements — •Patrick Stender, Guido Schmitz, Constantin Ene, and Henning Galinski — Institute of Material Physics, WWU Münster

Based on the thermodynamics of inhomogeneous systems, it is expected that the chemical transition at an interface between two immiscible components cannot be atomically sharp. Recently, we could demonstrate by atom probe tomography that interfaces of metallic multilayers are indeed of finite chemical width and that this width depends systematically on temperature in thermal equilibrium. Thus, the observed effect becomes especially important for multilayer periodicities in the nanometer range. In the case of GMR devices, it can be made responsible for thermal degradation.

In our work, the temperature dependence of the chemical width of layer interfaces of the binary systems Ag/Cu and Fe/Cr and the ternary system Cu/Ni81Fe19 is studied by atom probe tomography. Metallic triple and multilayers were deposited using ion beam sputter deposition technique. For all samples, an isochronal annealing was performed. Owing to the outstanding resolution of the atom probe tomography, a significant broadening of the interface is demonstrated on the depth scale between 1 and 2 nm.

Because all three systems are immiscible from a thermodynamic point of view and the derived activation energies are way too small to allow an interpretation by conventional interdiffusion, Cahn-Hilliard theory is used to explain the observed temperature dependence.