Berlin 2008 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Poster

DF 9.7: Poster

Tuesday, February 26, 2008, 15:00–18:00, Poster G

Probing nanoscale ferroelectricity by photoemission - the PbTiO₃ / Nb-SrTiO₃ (100) system — •Eike F. Schwier¹, Laurent Despont¹, Céline Lichtensteiger², Claude Monney¹, Corsin Battaglia¹, Matthew Dawber², Gunnar Garnier¹, Jean-Marc Triscone², and Philipp Aebi¹ — ¹Institut de Physique, Université de Neuchâtel, CH-2000 Neuchâtel, Switzerland — ²DPMC, Université de Genève, Switzerland

Ferroelectric thin films have become more and more important as possible substituents of ferromagnetic storage devices. To utilize these new materials within the lowered dimensionality of modern electronics, one has to investigate the limits of the films functionality. Two questions are especially important. Does a critical thickness for ferroelectricity exist? And what does the interaction of the electrodes with the film change inside the film?

We performed photoemission experiments on ultra thin PbTiO₃ films grown on Nb-SrTiO₃ (100) in order to probe the properties close to the surface and at the atomic scale. X-ray photoelectron diffraction maps are used to probe the intra-cell polar atomic distortion and tetragonality associated with ferroelectricity at the surface. Thickness and mean detection depth dependencies in X-ray photoelectron spectroscopy data lead to a semi-classical model which might be able to describe the electrostatic potential course across the system. To estimate the influence of sample charging versus the charge displacement created by the ferroelectricity, a time and intensity dependent shift in the photoelectron kinetic energy is exploited.