Polarization Scaling in Ultra-thin Epitaxial Ferroelectric Heterostructures: Experimental Results

ORAL

Abstract

Scaling of the structural order parameter and the polarization was investigated in ultra-thin epitaxial PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ /SrRuO$_{3}$/SrTiO$_{3}$ model ferroelectric heterostructures. High Resolution Electron Microscopy and Synchrotron X-Ray studies show that a high tetragonality (c/a$\sim $1.06) is maintained down to 40 {\AA} thick films, suggesting indirectly that ferroelectricity is fully preserved at such ultrathin thicknesses. However, measurement of the switchable polarization ($\Delta P)$ using a novel pulsed probe setup revealed a systematic drop from $\sim 140\mu C/cm^2$ for a 150 {\AA} thick film to $11\mu C/cm^2$ for a 40 {\AA} thick film. This contradiction between the structural measurements and the measured switchable polarization is explained by an increasing presence of a strong depolarization field, which creates a pinned 180$^{o}$ polydomain state for the thinnest films. This work was supported by MRSEC Grant {\#} 00-8008, DOE Grant DE-FG02-01ER45937 and NSF-DFG Grant 02-44288.

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Authors

  • Ramamoorthy Ramesh

    • Dept. of Materials Science and Engineering, and Dept. of Physics, Univ. of California, Berkeley CA 94720
    • Dept of Materials Science and Physics, University of California, Berkeley CA 94720
    • Univeristy of California, Berkeley
    • U C Berkeley
    • University of California, Berkeley

  • V. Nagarajan

  • J.Q. He

  • C. Jia

  • H. Kohlstedt

  • R. Waser

    • Center of Nanoelectronic Systems for Information Technology, Dept IFF, FZ- Juelich D52425

  • S. Prasertchoung

  • T. Zhao

    • Dept of Materials Science and Dept of Physics, University of California, Berkeley CA 94720

  • K. Lee

  • Y.K. Kim

  • S. Baik

    • Dept. Materials Science and Engineering, Pohang University of Science and Technology,Pohang 790-7