Boschetto Gabriele, Carapezzi Stefania, Todri-Sanial Aida
Laboratory of Computer Science, Robotics, and Microelectronics, University of Montpellier, CNRS 161 Rue Ada 34095 Montpellier France
Department of Electrical Engineering, Eindhoven University of Technology Groene Loper 3 5612 AE Eindhoven Netherlands.
Nanoscale Adv. 2023 Jul 21;5(16):4203-4212. doi: 10.1039/d3na00045a. eCollection 2023 Aug 8.
Non-volatile memristive devices based on two-dimensional (2D) layered materials provide an attractive alternative to conventional flash memory chips. Single-layer semiconductors, such as monolayer molybdenum disulphide (ML-MoS), enable the aggressive downscaling of devices towards greater system integration density. The "atomristor", the most compact device to date, has been shown to undergo a resistive switching between its high-resistance (HRS) and low-resistance (LRS) states of several orders of magnitude. The main hypothesis behind its working mechanism relies on the migration of sulphur vacancies in the proximity of the metal contact during device operation, thus inducing the variation of the Schottky barrier at the metal-semiconductor interface. However, the interface physics is not yet fully understood: other hypotheses were proposed, involving the migration of metal atoms from the electrode. In this work, we aim to elucidate the mechanism of the resistive switching in the atomristor. We carry out density functional theory (DFT) simulations on model Au and ML-MoS interfaces with and without the presence of point defects, either vacancies or substitutions. To construct realistic interfaces, we combine DFT with Green's function surface simulations. Our findings reveal that it is not the mere presence of S vacancies but rather the migration of Au atoms from the electrode to MoS that modulate the interface barrier. Indeed, Au atoms act as conductive "bridges", thus facilitating the flow of charge between the two materials.
基于二维（2D）层状材料的非易失性忆阻器件为传统闪存芯片提供了一种有吸引力的替代方案。单层半导体，如单层二硫化钼（ML-MoS），能够使器件积极地缩小尺寸，以实现更高的系统集成密度。“原子忆阻器”是迄今为止最紧凑的器件，已被证明能在其高电阻（HRS）和低电阻（LRS）状态之间进行几个数量级的电阻切换。其工作机制背后的主要假设依赖于器件运行期间金属接触附近硫空位的迁移，从而引起金属 - 半导体界面处肖特基势垒的变化。然而，界面物理尚未被完全理解：还提出了其他假设，涉及金属原子从电极的迁移。在这项工作中，我们旨在阐明原子忆阻器中电阻切换的机制。我们对有和没有点缺陷（空位或替代）的模型金和ML-MoS界面进行密度泛函理论（DFT）模拟。为了构建实际的界面，我们将DFT与格林函数表面模拟相结合。我们的研究结果表明，调节界面势垒的不是仅仅存在硫空位，而是金原子从电极迁移到二硫化钼。实际上，金原子充当导电“桥”，从而促进两种材料之间的电荷流动。
