Surface reconstruction and ferroelectricity in PbTiO3

M. SEPLIARSKY; M. G. STACHIOTTI; R. L. MIGONI

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

Año: 2005 vol. 72 p. 14110 - 14110

0163-1829

    Surface and ferroelectric properties of PbTiO3 thin fims are investigated using an interatomic potential approach with parameters determined from ï¬rst-principles calculations. We show that a model developed for the bulk describes properly the surface properties of PbTiO3. In particular, the antiferrodistortive surface reconstruction, recently observed with x-ray scattering, is correctly reproduced as a result of the change in the balance of long-range Coulombic and short-range interactions at the surface. The effects of the surface reconstruction on the ferroelectric properties of ultrathin ï¬lms are investigated. Under the imposed open-circuit electrical boundary conditions, the model gives a critical thickness for the ferroelectricity of four unit cells. The surface layer, which forms the antiferrodistortive reconstruction, participates in the ferroelectricity. A decrease in the tetragonality of the films leads to the stabilization of a phase with nonvanishing in-plane polarization. A peculiar effect of the surface reconstruction on the in-plane polarization profïle is found.