Coercive field modified via partial ion substitution, mechanical load and charge injection in (Ba, Ta, Cr) doped BiFeO3 films

Abstract

Changes in the coercive field of ferroelectric materials translate into variations in the operating power consumption of ferroelectric devices. Here, we have used partial ion substitution to reduce the coercive field in BiFeO3 films deposited by the pulsed laser technique. We have also used mechanical loads without interruption during switching events at the nanoscale to follow the changes in the coercive field. Furthermore, we have analyzed the dependence of the coercive field concerning the injected charges during the writing process. The partial ion substitution of Ba, Ta, and Cr in the BiFeO3 structure causes a reduction of ∼50% in the coercive field due to a weakening in the Asites-O bonds. The mechanical load experiments show that linearly increasing mechanical loading from ∼50 nN to ∼600 nN tends to increase the signal amplitude of the piezoresponse and move the coercive field locations. The linear unloading reduces the amplitude and returns the coercive field to values close to before the force experiment, pointing out a reversible process. Such behavior can be explained by considering that the piezoelectric response is supported and enhanced by the electric field created by the flexoelectric effect during the mechanical loading process due to the small tip radius. Finally, the application of negative (positive) voltage during the writing process caused the loops to shift to the left (right), changing the locations of the coercive field.