Understanding of Multiple Resistance States by Current-sweep Measurement and Compliance Current Modulation in 2D MoS2-based Non-volatile Resistance Switching Devices

Various two-dimensional materials, such as graphene oxide, solution-processed or phase-change transitional metal dichalcogenides (TMDs), degraded black phosphorus and multilayer hexagonal boron nitride (h-BN) [ 1 - 5 ], have been reported to exhibit non-volatile resistance switching (NVRS) phenomenon, in which the resistance can be reversibly switched between a high resistance state (HRS) and a low resistance state (LRS) through external electrical bias and maintained without power supply. Recently, we reported the observation of NVRS in single-layer TMDs and h-BN atomristors (memristor effect in atomically thin nanomaterials) with forming-free characteristic, large on/off current ratio (up to 10 7 ) and fast switching speed (< 15 ns) [ 6 - 8 ]. Here, to investigate the switching mechanisms in the 2D monolayers, we introduced a new electrical characterization method by current sweeping to illustrate the detailed information hidden in the commonly used voltage-sweep curves, showing multiple transition steps in the SET process. Moreover, by varying the SET compliance current in voltage-sweep measurement, multiple resistance states can be obtained with a range of five orders of magnitude. These results provide strong evidence for the previously reported conductive-bridge-like model of 2D atomristors [8] , and enable further applications in multi-bit data storage and analog-like neuromorphic computing.