Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 15: Thin Films and Nanostructures II

DF 15.4: Vortrag

Donnerstag, 26. März 2009, 11:40–12:00, WIL B321

Stabilization of out-of-plane polarization and head-to-head 180^∘ domain walls in ferroelectric materials — •Kourosh Rahmanizadeh, Gustav Bihlmayer, and Stefan Blügel — Institut für Festkörperforschung & Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany

Experimental studies suggest that defects play an important role in ferroelectric materials. Employing density functional theory calculations based on the full-potential linearized augmented planewave method as implemented in the FLEUR code (www.flapw.de), we studied the polarization perpendicular to the surface of thin films of the ferroelectric perovskites BaTiO₃ and PbTiO₃. Without an electric field that compensates the depolarization field a polarization perpendicular to the surface is not stable, but we can stabilize an out-of-plane polarization with different types of defects at the surface. This mechanism can also be at work at head-to-head and tail-to-tail 180^∘ domain walls, which can occur in these compounds. Although nominally a substantial extra charge is present at these surfaces or interfaces, the electronic properties are found to be very similar to the bulk of the perovskites.