Phase-field study on controlling R-phase domain structure in BiFeO3 thin films via scanning tip: effects of film thickness, tip bias and scanning speed

Abstract

BiFeO₃ (BFO) thin films at room temperature and moderate misfit strains favor to form rhombohedral phase (R-phase) ferroelastic domain patterns, and the coupling between the ferroelastic domain and antiferromagnetism makes it crucial to gain a deterministic control of the ferroelastic domain pattern in BFO thin films. So far, scanning tip electric field has been experimentally proven to effectively manipulate the ferroelastic domain pattern in BFO thin films. However, due to the complexity of the switching dynamics, the factors affecting the ferroelastic domain switching of BFO thin films under scanning tip electric field are still not completely understood. In this work, a comparative study based on phase-field simulations is made to reveal the effects of three factors including film thickness, tip bias and scanning speed on the switching of 71° R-phase ferroelastic stripe domain patterns in BFO thin films. It shows that the volume fractions of the tip-field-induced nucleated domain variants are modified by all the three factors and affect the subsequent spatial–temporal domain evolution during tip scanning, but their impacts on the final switching paths can be quite different. Specifically, the effect of decreasing the film thickness is similar to that of increasing the tip bias, with consistent switching paths. The tip scanning speed affects the size of domain nuclei but has a minor influence on the final switching path, consistent with our experimental observation. These results extend our current understanding of the domain switching in BFO thin films and should be instructive for practical applications.