Electrical hysteresis characteristics in photogenerated currents on laser-beam-derived in-plane lateral 1D MoS2-Schottky junctions

Abstract

Atomically thin two-dimensional transition-metal dichalcogenide materials with van der Waals integration provide various interesting optoelectronic characteristics that can be used to realize highly efficient flexible solar cells and photosensors. We previously reported in-plane lateral one-dimensional Schottky junctions (SJs) on few-atom-layer 2H-phase semiconductor-molybdenum disulfide by forming a 1T′-metal phase using laser beam (LB) irradiation and clarified their unique optoelectronic properties. Although the LB-derived 1T′/2H phase SJs provided efficient photocurrent generation, they had a large number of defects owing to the excess heat accumulation caused by the LB. Here, we observe partial electric hysteresis properties in photogenerated currents (Iphoto) on the SJs under reverse bias voltage regions and reveal that they are very sensitive to the voltage sweep direction and its switching (holding) time. The properties persist under dark ambient conditions for a few minutes, even after photo-irradiation is complete. The temperature dependence reveals that a defect-derived deep carrier trap-center, which is unique to the present 1T′ phase, can be the cause of these phenomena. A larger Iphoto and an increase in photogeneration efficiency are obtained by eliminating this trap center through thermal annealing. In contrast, it is expected that these hysteresis properties lead to atomically thin photo-memristor devices for opto-neuromorphic systems.