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

Changes in the coercive field of ferroelectric materials translate into variations in the operating power consumptionof ferroelectric devices. Here, we have used partial ion substitution to reduce the coercive field inBiFeO3 films deposited by the pulsed laser technique. We have also used mechanical loads without interruptionduring switching events at the nanoscale to follow the changes in the coercive field. Furthermore, we haveanalyzed the dependence of the coercive field concerning the injected charges during the writing process. Thepartial ion substitution of Ba, Ta, and Cr in the BiFeO3 structure causes a reduction of ~50% in the coercive fielddue to a weakening in the Asites-O bonds. The mechanical load experiments show that linearly increasing mechanicalloading from ~50 nN to ~600 nN tends to increase the signal amplitude of the piezoresponse and movethe coercive field locations. The linear unloading reduces the amplitude and returns the coercive field to valuesclose to before the force experiment, pointing out a reversible process. Such behavior can be explained byconsidering that the piezoelectric response is supported and enhanced by the electric field created by theflexoelectric effect during the mechanical loading process due to the small tip radius. Finally, the application ofnegative (positive) voltage during the writing process caused the loops to shift to the left (right), changing thelocations of the coercive field.