Theoretical phase diagram of ultrathin films of incipient ferroelectrics

Abstract

A first-principles-based scheme is used to compute the temperature-versus- misfit strain "Pertsev" phase diagram of ultrathin films of incipient ferroelectric KTa O3. The results suggest that, at variance with the bulk material, KTa O3 ultrathin films cannot be described as quantum paraelectrics. Rather, the behavior of the films is largely determined by surface/interface effects that favor ferroelectricity and the imperfect screening of the depolarizing fields. This leads to Pertsev phase diagrams that are qualitatively similar to those of normal ferroelectrics such as BaTi O3. © 2007 American Institute of Physics.