Adsorbate-Induced Ferroelectricity in Nanostructures

We discuss recent progress in understanding the size-dependent evolution of ferroelectricity in perovskite nanostructures and ultrathin films obtained via variable-temperature scanning probe microscopy investigations of individual nanorods and other ferroelectric nanostructures. We propose a mechanism in which the surface polarization charge is passivated by molecular adsorbates. A combination of density functional theory simulations, modified phenomenological Landau theory, and thermodynamic analysis demonstrates that the experimental behavior is well described by this mechanism.