The Role of Mobile Point Defects in Two-Dimensional Memristive Devices

TL;DR

This paper uncovers the crucial role of mobile defects in the switching behavior of 2D TMDC memristive devices, providing a charge transport model validated by experiments that advances understanding for neuromorphic computing.

Contribution

It introduces a comprehensive charge transport model highlighting mobile defects' role in switching, validated by experimental data, offering new insights into 2D TMDC memristive mechanisms.

Findings

Mobile defects dominate switching dynamics.

Formation and annihilation of vacancy zones control switching.

Minor interface potential changes lead to different behaviors.

Abstract

Two-dimensional (2D) layered transition metal dichalcogenides (TMDCs) are promising memristive materials for neuromorphic computing systems as they could solve the problem of the excessively high energy consumption of conventional von Neumann computer architectures. Despite extensive experimental work, the underlying switching mechanisms are still not understood, impeding progress in material and device functionality. This study reveals the dominant role of mobile defects in the switching dynamics of 2D TMDC materials. The switching process is governed by the formation and annihilation dynamics of a local vacancy depletion zone. Moreover, minor changes in the interface potential barriers cause fundamentally different device behavior previously thought to originate from multiple mechanisms. The key mechanisms are identified with a charge transport model for electrons, holes, and ionic point defects, including image-charge-induced Schottky barrier lowering (SBL). The model is validated by comparing simulations to measurements for various 2D MoS$_2$-based devices, strongly corroborating the relevance of vacancies in TMDC devices and offering a new perspective on the switching mechanisms. The insights gained from this study can be used to extend the functional behavior of 2D TMDC memristive devices in future neuromorphic computing applications.