Control of photocurrent and multi-state memory by polar order engineering in 2H-stacked α-In2Se3 ferroelectric

Controlling the polar order in ferroelectric materials may enrich the diversity of their property and functionality, offering new opportunities for the design of novel electronic and optoelectronic devices. In this paper, we report a planar multi-state memory device built upon a two-dimensional (2D) van der Waals layered ferroelectric material, 2H α-In2Se3. Three (high, median and low) resistance states are demonstrated to be interconvertible in this device with a fast switching speed, excellent endurance and retention performances via the modulation of the polar order of the ferroelectric α-In2Se3 layers under an in-plane electric field. Remarkably, reversible switching between the median-resistance state and the low-resistance state can be achieved by an ultralow electric field of 1–2 orders of magnitude smaller than the reported values in other 2D ferroelectric material-based memory devices. Furthermore, the three different polar order states are discovered to exhibit distinctive photo-responses. These results demonstrate great potentials of α-In2Se3 in nonvolatile high-density memory and advanced optoelectronic device applications.