Effect of grain boundaries on metal atom migration and electronic transport in 2D TMD-based resistive switches

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, such as Au, Cu, Al, Ni, and Ag, are examined, focusing on their migration both in the out-of-plane direction through a MoS₂ layer and along the surface of the MoS₂ layer, pertinent to filament formation in vertical and lateral memristors, respectively. Different types of GBs usually present in MoS₂ are considered to assess their influence on the diffusion of metal atoms. The findings are compared with those for structures based on pristine MoS₂ 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.