Unveiling the Fundamental Role of Temperature in RRAM Switching Mechanism by Multiscale Simulations.

Even though resistance switching memories (RRAMs) can be potentially employed in a broad variety of fields, such as electronics and brain science, they are still affected by issues that prevent their application in circuitry. These problems are a consequence of the lack of detailed knowledge about the physical processes occurring in the device. In this work, we propose multiscale simulations, combining kinetic Monte Carlo and finite difference methods, to shed light on the yet-unclear switching process occurring in the valence change RRAMs, which are believed to work as a consequence of the drift and diffusion of crystalline defects that act as dopants. Results show that the height of the defect diffusion barrier influences the switching process, the retention, and the switching time. In particular, nonvolatile switching can be achieved only by means of the fundamental role of temperature variations induced by Joule heating if the diffusion barriers of the defects are larger than ∼1 eV. High barriers prevent defects from hopping when no voltage is applied. During the transition from the high-resistance to the low-resistance state of the device, a heating stage of the material precedes the defect drift because the applied electric field by itself is not enough to lead to a drift velocity such that switching is achieved within microseconds. The temperature increase has, therefore, the double effect of activating the motion of the defects and enhancing their drift velocity. The switching process can occur only if a sufficiently high temperature is reached thanks to the Joule effect. On the basis of these findings, the RRAM design could aim at a better temperature management to achieve at the same time reproducibility and reliability.