Understanding Memristive Behavior: An Atomistic Study of the Influence of Grain Boundaries on Surface and Out-of-Plane Diffusion of Metallic Atoms

TL;DR

This paper investigates how grain boundaries in 2D materials influence metallic atom diffusion and electron conductance, affecting memristor switching performance through atomistic simulations.

Contribution

It provides a detailed atomistic analysis of metal atom migration across grain boundaries in 2D materials using DFT and NEGF, highlighting their impact on memristor behavior.

Findings

Grain boundaries significantly alter metal atom diffusion paths.

Different metals exhibit varied migration behaviors at grain boundaries.

Grain boundaries influence electron conductance and resistive switching ratios.

Abstract

Atomic migration from metallic contacts, and subsequent filament formation, is recognised as a prevailing mechanism leading to resistive switching in memristors based on two-dimensional materials (2DMs). This study presents a detailed atomistic examination of the migration of different metal atoms across the grain boundaries (GBs) of 2DMs, employing Density Functional Theory in conjunction with Non-Equilibrium Green's Function transport simulations. Various types of metallic atoms, Au, Cu, Al, Ni, and Ag, are examined, focusing on their migration both in the out-of-plane direction through a MoS\textsubscript{2} layer and along the surface of the MoS\textsubscript{2} layer, pertinent to filament formation in vertical and lateral memristors, respectively. Different types of GBs usually present in MoS\textsubscript{2} are considered to assess their influence on the diffusion of metal atoms. The findings are compared with structures based on pristine MoS\textsubscript{2} and those with mono-sulfur vacancies, aiming to understand the key elements that affect the switching performance of memristors. Furthermore, transport simulations are carried out to evaluate the effects of GBs on both out-of-plane and in-plane electron conductance, providing valuable insights into the resistive switching ratio.