  Memristors are prominent passive circuit elements with promising futures for
energy-efficient in-memory processing and revolutionary neuromorphic
computation. State-of-the-art memristors based on two-dimensional (2D)
materials exhibit enhanced tunability, scalability and electrical reliability.
However, the fundamental of the switching is yet to be clarified before they
can meet industrial standards in terms of endurance, variability, resistance
ratio, and scalability. This new physical simulator based on the kinetic Monte
Carlo (kMC) algorithm reproduces the defect migration process in 2D materials
and sheds light on the operation of 2D memristors. The present work employs the
simulator to study a two-dimensional $2H-MoS_2$ planar resistive switching (RS)
device with an asymmetric defect concentration introduced by ion irradiation.
The simulations unveil the non-filamentary RS process and propose practical
routes to optimize the device's performance. For instance, the resistance ratio
can be increased by 53% by controlling the concentration and distribution of
defects, while the variability can be reduced by 55% by increasing 5-fold the
device size from 10 to 50 nm. Our simulator also explains the trade-offs
between the resistance ratio and variability, resistance ratio and scalability,
and variability and scalability. Overall, the simulator may enable an
understanding and optimization of devices to expedite cutting-edge
applications.
