THICKNESS DEPENDENCE OF THE DIELECTRIC SUSCEPTIBILITY OF FERROELECTRIC THIN-FILMS

From the phenomenological theory, the size effects on dielectric properties of ferroelectric thin films were calculated. When the spontaneous polarization is reduced in the surface layer, the mean susceptibility of the film increases with the decrease in film thickness and a size-driven phase transition will take place at a critical thickness. If the temperature-driven phase transition of the bulk is a second-order one, the size-driven transition will be accompanied by a dielectric divergence; if it is a first-order transition, a finite dielectric peak will appear. When the spontaneous polarization is enhanced in the surface layer, the mean susceptibility of the film decreases with the decrease in film thickness. No size-driven phase transition and hence no dielectric anomaly will occur in this case. © 1994 The American Physical Society.