Size-driven phase transition in stress-induced ferroelectric thin films

We have developed a concise phenomenological theory to investigate phase transitions and dielectric properties of ferroelectric thin films under stress. When the polarization at the surface is greater than that in the interior of the film, competition between the ‘superpolarized’ surface and tensile stress leads to a ferroelectric–paraelectric transition above a critical stress. This model is appropriate for the data on stress-induced barium–strontium titanate (BST) thin-film ferroelectric memory devices [Jpn. J. Appl. Phys. 36 (1997) 5846]. Stress–thickness phase diagrams are presented for PbTiO3 and BaTiO3 ferroelectric thin films.