Surface effects and ferroelectric phase transitions in BaTiO 3 ultrathin films

TINTE, S.; STACHIOTTI, M. G.

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

AMER PHYSICAL SOC

Año: 2001 vol. 64

0163-1829

We present a finite-temperature study of ferroelectric phase transitions in BaTiO3 ultrathin films using anatomic-level simulation approach. This is based on a shell model for BaTiO3 with parameters obtained fromfirst-principles calculations. While transitions involving in-plane electric polarization are practically unper-turbed by the presence of the surface, surface atomic relaxations act as a strong perturbation on the ferroelectricorder perpendicular to the surface. However, a strain induced ferroelectric polydomain phase with an out-of-plane orientation of polarization is stabilized in a not short-circuited film as thin as 20 Å. A reduction of theout-of-plane polarization at the film surface is observed.