Relaxor ferroelectric thin-film heterostructures: Scaling of dielectric properties

Abstract

An experimental study of the dielectric behavior of relaxor ferroelectric (RFE) thin-film capacitor heterostructures and a separate analysis of the dielectric properties of the RFE films are presented. Epitaxial heterostructures of RFE PbMg_1/3Nb_2/3O₃, PbSc_0.5Nb_0.5O₃, PbMg_1/3Nb_2/3O₃-PbTiO₃ and PbSc_0.5Nb_0.5O₃-PbTiO thin films (100–500 nm) with La_0.5Sr_0.5CoO₃ bottom and Pt top electrodes were fabricated by in situ pulsed laser deposition on MgO (1 0 0) and LaAlO₃(1 0 0). Dielectric properties of the heterostructures were studied as a function of frequency (10²–10⁶ Hz), temperature (77–725 K), and amplitude of applied a.c. field (10²–10⁶ V m⁻¹). The contribution of the film/electrode interfaces to the properties of the heterostructures was evaluated using a model of a series capacitor connection of the film and passive interface layers. The characteristics of the interface layers were experimentally found from the temperature evolution of the dielectric response of the heterostructures, and the true properties of the films were reconstructed. In the films, all typical features of RFE were found to be essentially similar to those in single crystals. Also, it was shown that in heterostructures, both a “relaxor-like” behavior and an apparent dielectric nonlinearity can be determined by the film/electrode interface rather than by the films.