Highly-strained coherent interfaces, between rhombohedral-like (R) and tetragonal-like (T) phases in BiFeO3 thin films, often show enhanced electrical conductivity in comparison to non-interfacial regions. In principle, changing the population and distribution of these interfaces should therefore allow different resistance states to be created. However, doing this controllably has been challenging to date. Here, we show that local thin film phase microstructures (and hence R-T interface densities) can be changed in a thermodynamically predictable way (predictions made using atomistic simulations) by applying different combinations of mechanical stress and electric field. We use both pressure and electric field to reversibly generate metastable changes in microstructure that result in very large changes of resistance of up to 108%, comparable to those seen in Tunnelling Electro-Resistance (TER) devices.

Strained bismuth ferrite thin films unite a wealth of functional properties 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 behaviour 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 R/T 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, which also leads to initially uniform T phases 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.

Correction for ‘Giant resistive switching in mixed phase BiFeO3via phase population control’ by David Edwards et al., Nanoscale, 2018, 10, 17629–17637.

The localized crystallography of conducting and non-conducting phase boundaries in mixed-phase BiFeO3 is directly compared using scanning transmission electron microscopy techniques.