Dynamic strain-induced giant electroresistance and erasing effect in ultrathin ferroelectric tunnel-junction memory

Strain engineering plays a critical role in ferroelectric memories. In this work, we demonstrate dynamic strain modulation on tunneling electroresistance in a four-unit-cell ultrathin BaTiO₃ metal/ferroelectric/semiconductor tunnel junction by applying mechanical stress to the device. With an extra compressive strain induced by mechanical stress, which is dynamically applied beyond the lattice mismatch between the BaTiO₃ layer and the Nb : SrTiO₃ substrate, the ON/OFF current ratio increases significantly up to a record high value of 10⁷, whereas
a mechanical erasing effect can be observed when a tensile stress is applied. This dynamic strain engineering gives rise to an efficient modulation of ON/OFF ratio due to the variation of BaTiO₃ polarization. This result sheds light on the mechanism of electroresistance in the ferroelectric tunnel junctions by providing direct evidence for polarization-induced resistive switching, and also provides another stimulus for memory state operation.