Formation of self-organized nanodomain arrays in triglycine sulfate crystal by rapid cooling

Abstract

We have studied the formation of self-organized nanodomain arrays in nominally pure triglycine sulfate single crystals induced by cooling samples below phase transition. The initial striped domain structure was created by thermal pretreatment that consisted of annealing samples above the Curie temperature and subsequent cooling. It was shown that several quasi-regular arrays of submicron elongated domains appeared after cooling, consisting of up to four generations. The first generation of domain arrays appears at the center of the initial striped domain. The average length of isolated domains in these arrays decreases with the generation number by the power law. The domains of the arrays of the first generation demonstrate a lenticular shape for the initial domain width below 10 μm and a dashed shape for wider domains. The experimental results obtained were explained in terms of the kinetic approach based on consideration of the domain structure evolution as a result of nucleation governed by the polar component of the spatially nonuniform electric field consisting of two main inputs: a pyroelectric fieldinduced by temperature change and an uncompensated depolarization field that appeared as a result of domain formation. Calculations revealed the field maximum at the domain center leading to the formation of an unstable comb-like domain, which transforms into arrays of isolated domains under the action of the depolarization field. Further cooling leads to the formation of domain arrays of the second generation. The obtained results are important for understanding the general mechanisms of the formation of multiscale hierarchical domain structures in ferroelectrics. They pave the way toward the utilization of self-organization processes in domain engineering for the creation of functional quasi-regular domain structures.