Polarization loop deformations of an oxygen deficient Pb(Zr0.25,Ti0.75)O3 ferroelectric thin film

Abstract

An epitaxial oxygen deficient Pb(Zr0.25,Ti0.75)O3 (PZT) thin film, which presented hysteresis loop with significant shift along the electric field axis and apparent polarization suppression, is investigated. Loop deformations are studied and entirely explained, both qualitatively and quantitatively by simulations including the effect of an ultrathin interfacial layer uniformly charged. The method developed in this paper is suitable to calculate not only the polarization due to the switching domains, but also all the characteristics of the space charge layer. The determination of the linear dielectric constant of the bulk ferroelectric layer does not require preparation of films with different thicknesses, unlike most of the methods proposed to date. Linear dielectric constant and thickness of the interfacial layer are in the range εil=80–130 and dil=8–12nm, respectively. On the other hand, a very large interfacial charge concentration (Nil of few 1026m−3) is obtained. For the studied PZT sample, hysteresis deformations are not attributable to pinning of domain walls, despite the large value of Nil, but rather to the interfacial space charge layer that screens the applied electric field and prevents the full switching of the ferroelectric domains.