Recently, memristor (anion-based memristor) is referred to as the forth circuit element which resistance can be changed by the electric pulse signals that have been applied to it [1]. Moreover, the stored information in a memristor is non-volatile and also the resistance of a memristor can vary, through intermediate states, between high and low resistance states, by tuning the voltage and current. Therefore the memristor can be applied for analogue memory and/or learning device. Usually, memristive behavior is easily observed in the most transition metal oxide system, and it is explained by electrochemical migration of anion with electric field, electron scattering and joule heating. So far, memristors have been realized in one-dimensional (1D) structure with two terminal system (an oxide layer sandwiched between two metal contacts).

In this talk, I will present the experimental realization of a multi-terminal memtransistor from polycrystalline monolayer MoS2 , for a new neuromorphic circuit element called a “memtransistor” that combines the nonvolatility of a memristor with the gate-tunability of a transistor. Two-dimensional (2D) MoS2 memtransistors show gate tunability in individual states by four orders of magnitude in addition to large switching ratios with high cycling endurance and long-term retention of states. In addition to conventional neural learning behavior such as long-term potentiation and depression, multi-terminal MoS2 memtransistors possess gate-tunable heterosynaptic functionality that is not achievable using two-terminal memristors. For example, the conductance between a pair of two floating electrodes (pre- synaptic and post-synaptic neurons) is varied by an order of magnitude by applying voltage pulses to modulatory terminals. In situ scanning probe microscopy, cryogenic charge transport measurements, and device modeling reveal that bias-induced MoS2 defect motion drives resistive switching by dynamically varying Schottky barrier heights. Overall, the seamless integration of a memristor and transistor into one multiterminal device has the potential to enable complex neuromorphic learning in addition to providing opportunities for studying the unique physics of defect kinetics in 2D materials [2]. And 2D memtransistor system allow us to realize new function ‘gate tunable potentiation and depression’.