Ultra-flat BaTiO3 epitaxial films on Si(001) with large out-of-plane polarization

Abstract

Ferroelectric BaTiO3 is rarely used in monolithic Si devices due to the low quality of BaTiO3 films on Si, as polycrystallinity, degradation of bottom Pt electrodes, low polarization, and high roughness. Here, we overcome these limitations by using a buffer structure that combines yttria-stabilized zirconia, CeO2, and conducting LaNiO3. BaTiO3 films on the multilayered buffer, with total thickness of the buffer below 100 nm, are epitaxial, display remnant polarization of 6–10 μC/cm2, and have roughness of a few Å. These unprecedented properties pave the way to integrate ferroelectric BaTiO3 into Si platforms.