IMPACT OF THE AMBIENT HUMIDITY ON THE KINETICS OF FORMATION OF FERROELECTRIC DOMAINS IN MONOCRYSTALLINE LiTaO3

In this communication, we study the role of the water layer present on the surface of a ferroelectric layer during the growth of ferroelectric domains in a single crystal of congruent LiTaO3, by comparing results from atomic force microscopes operating in controlled atmosphere and in air. The overall kinetics of growth of domains is clearly slower under low relative humidity ( RH), which suggests that the water layer present at the surface of the ferroelectric film plays an active role in the propagation of the domains. A finite element model is proposed in order to explain the differences, where the electric potential can propagate beyond the area of the tip in a conductive top layer adsorbed on the ferroelectric sample, this propagation being responsible for the switching of the polarization when the field is locally larger than the coercive field. According to this model, which describes fairly well the experimental observations, the growth of the domain can be described not only by a thermally activated process, but also using a purely electrical model, which strongly depends on the electrical properties of the layer covering the ferroelectric material.