Effects of dislocations with different locations, orientations and density on domain evolution of ferroelectric thin film: A phase field study

Abstract

The effects of dislocations on polarization distribution and switching in ferroelectric thin films are discussed based on a modified multi-field coupling theoretical framework that combining the flexoelectric effect and the strain field caused by dislocations. First, the correctness of the model is verified through a study about the effects of different flexocoupling types on domain structures around the dislocations. Then, effects of dislocations with different locations, orientations and density are systematically studied. Dislocations in the film will induce the appearance of a-domain. And the size of the new a-domain depends on the orientations and locations of dislocations. Among [001¯], [101¯] and [100] oriented single dislocations, the size of the new a-domain near the [101¯] oriented dislocation is the largest. It is essential to avoid generating [100] and [101¯] oriented dislocations since the [101¯] oriented dislocations can cause imprint failure and [100] oriented dislocations bring intense pinning effects. As the density of dislocations increases, the pinning effect and imprint behavior becomes stronger. The hysteresis loop of the film with [100] oriented multi-dislocations shows no ferroelectricity once the density reaches a certain limit. These dislocations induced imprint behavior and pinning effect can be eliminated by a larger applied electric field when the dislocation density is low. But when the dislocation density gets higher, the situation is different.