Local ferroelectric domain switching phenomenon in PbTiO₃ thin films affected by the imprint effect and external force

We investigated the local ferroelectric domain switching phenomena in PbTiO₃ (PTO) thin films, which were affected by both the imprint effect and the flexoelectric effect. DPTO/PTO multilayer films, in which an oxygen-deficient PbTiO_3-<i>δ</i> (DPTO) layer was formed on a PTO layer, exhibited imprinted ferroelectric hysteresis loops. The DPTO/PTO thin films, which exhibit improved energy storage characteristics due to the imprint effect, showed a decrease in the local ferroelectric domain switching voltage when switched in a specific direction. The ferroelectric nanobits formed by local domain switching in the DPTO/PTO thin film at a relatively low voltage, with switching voltages reduced by the imprint effect of the DPTO/PTO thin film, showed a decrease in the diameter compared to those in the PTO thin film. Additionally, we confirmed through first-principles calculations that when an external force is locally applied, the activation energy in the local area is lowered by the flexoelectric effect in the DPTO/PTO thin film. It has been experimentally confirmed that the reduction in activation energy in the local area, induced by the flexoelectric effect resulting from an external force applied to DPTO/PTO thin films, helps lower the local domain switching voltage.