Nature of point defects in monolayer MoS2 and the MoS2/(111)Au heterojunction

TL;DR

This study investigates how point defects and strain in monolayer MoS2 and its heterojunction with Au influence electronic properties and resistive switching, with implications for memristive device performance.

Contribution

It provides new insights into defect-induced midgap states and how strain and substrate interactions affect switching behavior in MoS2-based memristors.

Findings

Strain lowers Au+defect adsorption/desorption energies, improving switching energies.

Strain reduces the switching ratio between conductive states.

Charge transfer causes permanent polarization, affecting device variability.

Abstract

Deposition of MoS2 on (111)-Au alters the electronic properties of MoS2. In this study, we investigate the free-standing MoS2 monolayer and the MoS2~\(111)-Au heterostructure, with and without strain, as well as defects of interest in memristive and neuromorphic applications. We focus on so-called atomristor devices based on monolayer materials that achieve resistive switching characteristics with the adsorption and desorption of metal adatoms. Our study confirms that the formation of midgap states is the primary mechanism behind the resistive switching. Our results show that strain lowers the adsorption~\desorption energies of Au+defect structures of interest, leading to more favorable switching energies, but simultaneously reduces the switching ratio between states of differing conductivities. The presence of the (111)-Au substrate additionally introduces non-uniform amounts of strain throughout and charge transfer to the MoS2 monolayer. We propose that the induced strain can contribute to the experimentally observed n- to p-type transition and Ohmic to Schottky transition in the MoS2 monolayer. The charge transfer leads to a permanent polarization at the interface, which can be tuned by strain. Our study has important implications on the role of the electrode as being a source of the observed variability in memristive devices and as serving as an additional degree of freedom for tuning the switching characteristics of the memristor device.