Unveiling the Interfacial Behavior of Au Contacted MoS2 Atomristor and the Role of Point Defects

The recent demonstration of atomristors (Metal-Monolayer 2-D Material-Metal) has paved a path for high-density low power nonvolatile memories. Though nonvolatile resistive switching (NVRS) in atomristors has been demonstrated using various monolayer 2-D materials, much of the underlying physics behind their working is not yet clear. In this work for the first time, density functional theory (DFT) is used to investigate the behavior of various point defects (vacancies and gold atom adsorption therein) in the local region around them in the Au-MoS2-Au atomristor. The study reveals that monosulfur vacancies at one of the Au-MoS2 interfaces degrade electron injection or exit across another interface of the atomristor due to an increase in the tunneling barrier and width. However, molybdenum and disulfur vacancies reduce these barriers and widths at both the interfaces of an atomristor. Similar behavior is observed with Au atom adsorption at monosulfur and disulfur vacancies. The Au atom adsorption at disulfur vacancy reduces the exit barrier significantly and acts as a conductive point bridge between MoS2 and Au metal across the vdW gap, providing a low resistive path which is in excellent agreement with the recent experiment. Moreover, the investigations using Ab initio molecular dynamics (AIMD) indicate the low resistance state to be stable and nonvolatile. Furthermore, hybrid functional HSE06 was utilized to validate GGA- revPBE calculations wherein a good agreement between the two functionals was obtained. Our study provides physical insights into the role of various point defects in Au-MoS2-Au atomristors and provides defect engineering guidelines for NVRS.