Wafer-Scale Memristor Array Based on Aligned Grain Boundaries of 2D Molybdenum Ditelluride for Application to Artificial Synapses

2D materials have attracted attention in the field of neuromorphic computing applications, demonstrating the potential for their use in low-power synaptic devices at the atomic scale. However, synthetic 2D materials contain randomly distributed intrinsic defects and exhibit a stochasitc forming process, which results in variability of switching voltages, times, and stat resistances, as well as poor synaptic plasticity. Here, this work reports the wafer-scale synthesis of highly polycrystalline semiconducting 2H-phase molybdenum ditelluride (2H-MoTe2) and its use for fabricating crossbar arrays of memristors. The 2H-MoTe2 films contain small grains (≈30 nm) separated by vertically aligned grain boundaries (GBs). These aligned GBs provide confined diffusion paths for metal ions filtration (from the electrodes), resulting in reliable resistive switching (RS) due to conductive filament confinement. As a result, the polycrystalline 2H-MoTe2 memristors shows improvement in the RS uniformity and stable multilevel resistance states, small cycle-to-cycle variation (83.7%), and long retention times (>104 s). Finally, 2H-MoTe2 memristors show linear analog synaptic plasticity under more than 2500 repeatable pulses and a simulation-based learning accuracy of 96.05% for image classification, which is the first analog synapse behavior reported for 2D MoTe2 based memristors.