Dresden 2003 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 8: Dielektrische und ferroelektrische Schichten, Nanostrukturen und Rastermethoden

DF 8.2: Vortrag

Donnerstag, 27. März 2003, 10:10–10:30, HSZ/403

Current Transport and Size-Effects in ultra-thin Ferroelectric Barriers — •Hermann Kohlstedt¹, Julio Rodriguez Contreras¹, Ulrich Poppe¹, Juergen Schubert², and Rainer Waser¹ — ¹Forschungszentrum Jülich, Institut für Festkörperforschung (IFF-EKM), 52425 Jülich, Germany — ²Forschungszentrum Jülich, Institut für Schichten und Grenzflächen (ISG-1), 52425 Jülich, Germany

Non-volatile memories based on ferroelectric polarization reversal are currently under development for applications. There is an ongoing debate concerning the superparaelectric limit in ferroelectricity. Recent theoretical work, either with ab-initio techniques or by using the mean-field approach predict ferroelectricity in films down to a few number of unit cells ( 1−5 nm), for compressively strained thin films.

In this talk we review our development of so-called ferroelectric tunnel junctions with the following layer sequence: SrTiO₃ (substrate)/ SrRuO₃ (electrode)/ BaTiO₃ or PbZrxTi_1−xO₃ (ferroelectric)/ SrRuO₃ or Pt as a top electrode. These heterostructures have been investigated by XRD, RBS, scanning probe techniques and high-resolution TEM. The aim of our work is to study fundamental aspects of electron tunnelling and electron transport through a ferroelectric material as well as the influence of the transport current on the ferroelectric polarization state of the barrier material.

After fabricating tunnel junctions with areas down to 4 µ m² we studied the current transport. At voltages of approximately 600 mV clear switching events were observed. The origin of these switching will be discussed.