Switching Mechanism in Triglycine Sulfate and Other Ferroelectrics

The reversal of the spontaneous polarization in a ferroelectric crystal is governed by two mechanisms: the nucleation of new domains and the growth of these domains by domain wall motion. We have investigated the switching properties of triglycine sulfate (TGS) as a function of applied electric field, temperature, and thickness of the samples.It is proposed that at low fields nucleation is the slower mechanism and hence dominates the switching process while at high fields domain wall motion determines the rate of switching. The former process leads to an exponential dependence of switching time on applied electric field and the latter to a linear dependence.A model for the nucleation and domain wall motion is treated mathematically and is compared with experimental observations. The shape of the switching current pulse was found to yield much information. The shape depends strongly on the applied electric field and is correlated with the nucleation time as well as the domain wall motion time. The asymmetry of the pulse increases with decreasing field and can be associated with the interaction between domains and domain nuclei. This interaction in various ferroelectrics is discussed and its relation to the switching is considered.