Non-volatile resistive switching, also known as memristor¹ effect, where an electric field switches the resistance states of a two-terminal device, has emerged as an important concept in the development of high-density information storage, computing and reconfigurable systems^{2,3,4,5,6,7,8,9}. The past decade has witnessed substantial advances in non-volatile resistive switching materials such as metal oxides and solid electrolytes. It was long believed that leakage currents would prevent the observation of this phenomenon for nanometre-thin insulating layers. However, the recent discovery of non-volatile resistive switching in two-dimensional monolayers of transition metal dichalcogenide^10,11 and hexagonal boron nitride¹² sandwich structures (also known as atomristors) has refuted this belief and added a new materials dimension owing to the benefits of size scaling^10,13. Here we elucidate the origin of the switching mechanism in atomic sheets using monolayer MoS₂ as a model system. Atomistic imaging and spectroscopy reveal that metal substitution into a sulfur vacancy results in a non-volatile change in the resistance, which is corroborated by computational studies of defect structures and electronic states. These findings provide an atomistic understanding of non-volatile switching and open a new direction in precision defect engineering, down to a single defect, towards achieving the smallest memristor for applications in ultra-dense memory, neuromorphic computing and radio-frequency communication systems^2,3,11.

在高密度信息存储，计算和可重配置系统²的开发中，非易失性电阻切换（也称为忆阻器¹效应）已成为一个重要概念，其中电场会切换两端设备的电阻状态。^{3,4,5,6,7,8,9}。过去十年见证了诸如金属氧化物和固体电解质之类的非易失性电阻开关材料的巨大进步。长期以来，人们一直认为泄漏电流会阻止在纳米级薄绝缘层中观察到这种现象。然而，最近发现在过渡金属二卤化双金属化物^10,11和六方氮化硼¹²的二维单层中具有非易失性电阻转换夹层结构（也称为原子电阻器）已经驳斥了这种观点，并由于尺寸缩放的好处^10,13而增加了新的材料尺寸。在这里，我们阐明了使用单层MoS _2的原子片中转换机制的起源。作为模型系统。原子成像和光谱分析表明，金属被置换成硫空位导致电阻的非易失性变化，这通过缺陷结构和电子态的计算研究得到了证实。这些发现提供了对非易失性开关的原子性理解，并为精密缺陷工程（直至单个缺陷）打开了一个新的方向，以实现用于超密度存储器，神经形态计算和射频通信系统²的最小忆阻器^{2。 3,11}。