Functionalized double transition metal Mo₂Ti₂C₃T_x ferroelectric MXene and laser-reduced graphene based flexible memristors for next-generation two-dimensional ferrotronics

The emergence of two-dimensional (2D) mixed transition metal MXenes has notably broadened the scope of 2D layered materials towards a wide variety of applications. Here, we report for the first time the induced ferroelectricity in free-standing Mo₂Ti₂C₃T_x MXene film after undergoing simple heat treatment and its utilization as an active functional layer for non-volatile resistive random-access memory. The ferroelectric response, oxide phase formation and memory storage kinetics of the free-standing heated Mo₂Ti₂C₃T_x film outperformed the pristine non-heated Mo₂Ti₂C₃T_x. Ferroelectric behavior was observed solely in heated Mo₂Ti₂C₃T_x owing to the formation of TiO₂ with typical butterfly dielectric constant loop. Specifically, by utilizing the adaptive property of graphene oxide to reduce into conductive graphene sheets amid laser scribing, a tri-layer memristor structure Laser reduced graphene/heated Mo₂Ti₂C₃T_x/Laser reduced graphene was fabricated and analyzed against the Laser reduced graphene/non-heated Mo₂Ti₂C₃T_x/Laser reduced graphene device scheme. The former tri-layer free-standing scheme exhibited controlled conduction filament formation showcasing excellent resistive switching, sufficient memory window of R_off/R_on = 10² and excellent cycle-to-cycle endurance of up to 10³ cycles. This finding reveals the remarkable potential of double transition MXenes to be used as functional middle layer, which was not yet explored in resistive RAM memory storage elements, hence opening the door for another domain of applications i.e. neuromorphic computing and ferroelectronics based on non-volatile memory.