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

Abstract

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 $\mathrm{BaTi}{\mathrm{O}}_{3}$ 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 $\mathrm{BaTi}{\mathrm{O}}_{3}$ layer and the $\mathrm{Nb}:\mathrm{SrTi}{\mathrm{O}}_{3}$ substrate, the ON/OFF current ratio increases significantly up to a record high value of ${10}^{7}$, 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 $\mathrm{BaTi}{\mathrm{O}}_{3}$ 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.