Theoretical phase diagram of ultrathin films of incipient ferroelectrics

A first-principles-based scheme is used to compute the temperature-versus-misfit strain Pertsev phase diagram of ultrathin films of incipient ferroelectric KTaO3. The results suggest that, at variance with the bulk material, KTaO3 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 BaTiO3. (c) 2007 American Institute of Physics.