Ferroelectric Bi3.25La0.75Ti3O12 Films of Uniform a-Axis Orientation on Silicon Substrates
Ho Nyung Lee,
Dietrich Hesse,
Nikolai Zakharov,
Ulrich Gösele
The use of bismuth-layered perovskite films for
planar-type nonvolatile ferroelectric random-access memories requires
films with spontaneous polarization normal to the plane of growth.
Epitaxially twinned a axis-oriented La-substituted
Bi4Ti3O12 (BLT) thin films whose spontaneous polarization is entirely along the film normal were
grown by pulsed laser deposition on yttria-stabilized zirconia-buffered Si(100) substrates using SrRuO3 as bottom electrodes. Even
though the (118) orientation competes with the (100) orientation,
epitaxial films with almost pure (100) orientation were grown using
very thin, strained SrRuO3 electrode layers and kinetic
growth conditions, including high growth rates and high oxygen
background pressures to facilitate oxygen incorporation into the
growing film. Films with the a-axis orientation and having
their polarization entirely along the direction normal to the film
plane can achieve a remanent polarization of 32 microcoulombs per
square centimeter.
Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120
Halle/Saale, Germany.
