Theoretical Aspects of Phase Transitions in Ferroelectric Thin Films.

Phase transitions in ferroelectric thin films are discussed theoretically on the basis of the Tilley-Zeks model for the case where the transition is of the second order. A surface is characterized by an extrapolation length δ, which is a key concept of the model. For a positive δ the ferroelectric phase transition tends to be suppressed, with a decreasing transition temperature, while for a negative δ ferroelectricity tends to be enhanced, with an increasing transition temperature. Not only symmetric-surface cases, but also asymmetric-surface cases are discussed. [ABSTRACT FROM AUTHOR]