Electromechanical-mnemonic effects in BiFeO3 for electric field history-dependent crystallographic phase patterning

Strained bismuth ferrite thin films unite a wealth of functional properties Published online: including ferroelectricity, ferromagnetism, electrooptic coupling and interface-mediated conductivity. The coexistence of rhombohedral (R) and tetragonal (T) phases in these films further contributes to their versatility, as structural transitions can modify functional behavior and be leveraged to engineer properties such as electrochromism, magnetic characteristics, electromechanical response and charge transport. However, potential device applications necessitate precise control of the location and size of R and T phases and associated microstructures. Here, distinct RT phase patterns of different spatial expanse are obtained by appropriately pre-poling the film by applying an electric field with an atomic force microscope tip during scanning, as well as through local application of a certain sequence of voltage pulses. Moreover, the impact of field history on ferroelectric characteristics is investigated, providing further opportunities to tailor functional behavior.