Dresden 2006 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 2: Dielectric and Ferroelectric Thin Films and Nanostructures I

DF 2.2: Vortrag

Montag, 27. März 2006, 15:10–15:30, M{\"U}L Elch

Towards Ferroelectric Tunnel Junctions — •Alexander Kaiser, Adrian Petraru, Ulrich Poppe, Nicholas Pertsev, Hermann Kohlstedt, and Rainer Waser — Institut für Festkörperforschung (IFF-IEM) and Center of Nanoelectronic Systems for Information Technology (CNI), Forschungszentrum Jülich, 52425 Jülich

Experimental results showed evidence that ferroelectric phase is maintained even in a few nanometers thick ferroelectric films. If such an ultra-thin ferroelectric film is placed in between two electrodes, a so-called ferroelectric tunnel junction (FTJ) is obtained. Recent theories predict that the direct electron tunneling current through these ultra-thin ferroelectric films may be modified by the polarization state of the ferroelectric [1]. The piezoelectric effect, interface effects and the depolarization field may lead to a giant electroresistance (GER) [2] switching effect. For studying this behaviour we deposited SrRuO₃ (electrode)/BaTiO₃ (ferroelectric)/SrRuO₃ on SrTiO₃ (001) substrates by high-pressure sputtering. The film thickness of the ferroelectric BaTiO₃ was varied between 200 nm and 3 nm. AFM, XRD and TEM measurements show high cristalline quality with clear epitaxial BaTiO₃/SrRuO₃ interfaces. P−V and C−V measurements demonstrate ferroelectricity down to BaTiO₃ thickness of 5 nm. Tunnel junctions were fabricated in a four point geometry and I-V characteristics were measured between 300 K and 4.2 K. The I−V curves will be discussed in the framework of the I−V characteristics predicted by theory.

[1] Kohlstedt et al., Phys. Rev. B 72, 125341 (2005)

[2] Zhuravlev et al., Phys. Rev. Lett. 94, 246802 (2005)