Exascale transport simulations for the understanding of the switching mechanism in atomically thin memristors

Non-volatile resistive switching (NVRS) is an important concept in developing high-density information storage and computing. The recent discovery of NVRS in two-dimensional (2D) monolayer structures, such as MoS 2 and hexagonal boron nitride (hBN), opens a new avenue for memory/computing devices at the ultrathin scale. However, the fundamental switching mechanism in 2D monolayers is not yet fully understood. It is hypothesized that vacancies in 2D monolayers mediate the formation of conducting filamentary channels, transforming a high- to low-resistance state. But, to fully unravel the switching mechanism, it is highly desirable to simulate the electronic transport in a realistic device geometry using ab initio approaches for comparison with experimental data. We report results from simulations of electronic transport of ~1000 atom systems consisting of a hBN monolayer sandwiched between gold electrodes and compute I-V curves using the Real-space MultiGrid (RMG) code on Frontier exascale supercomputer at ORNL. Systematic NEGF calculations uncover why experimental devices exhibit a wide range of current ON/OFF ratios and provide a deeper understanding of the resistive switching mechanism in atomically thin memristors. This work was conducted at CNMS, a DOE-Science User Facility.