Nature|基于单层二硫化钼的多端记忆晶体管

文章链接：https://www.nature.com/articles/nature25747

二硫化钼记忆晶体管结构

摘要

忆阻器是一种双端无源电路元件，已开发用于非易失性电阻随机存取存储器，也可用于神经形态计算。忆阻器比闪存有更高的耐久性和更快的读/写时间，并能提供多位数据存储。然而，尽管双端忆阻器已经显示出了基本神经功能的能力，但人脑中的突触数量是神经元数量的1000倍以上，这意味着需要多端忆阻器来执行复杂的功能，如异源性突触可塑性（heterosynaptic plasticity）。先前尝试超越双端忆阻器的尝试，如三端Widrow–Hoff忆阻器和带纳米离子栅或浮栅的场效应晶体管，都没有实现晶体管的忆阻开关。在此，我们报告了在可扩展的制造过程中，使用多晶硅单分子层二硫化钼(MoS2)的多端混合忆阻器和晶体管(即忆阻晶体管)的实验实现。二维MoS2记忆晶体管在单个电阻状态下显示出4个数量级的门可调性，以及大开关比、高循环耐久性和长期状态保持。除了传统的长期增强/抑制的神经学习行为，六端MoS2 记忆晶体管具有栅可调谐异源性突触的功能，这是使用双端忆阻器无法实现的。例如，一对浮动电极(突触前和突触后神经元)之间的电导通过对调节终端施加电压脉冲而改变约10倍。原位扫描探针显微镜、低温电荷传输测量和器件模型显示，偏压诱导的MoS2缺陷运动通过动态变化肖特基势垒高度来驱动电阻开关。总的来说，将忆阻器和晶体管无缝集成到一个多终端器件中，可以实现复杂的神经形态学习和二维材料缺陷动力学物理研究

Memristors are two-terminal passive circuit elements that have been developed for use in non-volatile resistive random-access memory and may also be useful in neuromorphic computing. Memristors have higher endurance and faster read/write times than flash memory and can provide multi-bit data storage. However, although two-terminal memristors have demonstrated capacity for basic neural functions, synapses in the human brain outnumber neurons by more than a thousandfold, which implies that multiterminal memristors are needed to perform complex functions such as heterosynaptic plasticity. Previous attempts to move beyond two-terminal memristors, such as the three-terminal Widrow–Hoff memristor and field-effect transistors with nanoionic gates or floating gates, did not achieve memristive switching in the transistor. Here we report the experimental realization of a multiterminal hybrid memristor and transistor (that is, a memtransistor) using polycrystalline monolayer molybdenum disulfide (MoS2) in a scalable fabrication process. The two-dimensional MoS2 memtransistors show gate tunability in individual resistance states by four orders of magnitude, as well as large switching ratios, high cycling endurance and long-term retention of states. In addition to conventional neural learning behaviour of long-term potentiation/ depression, six-terminal MoS2 memtransistors have gate-tunable heterosynaptic functionality, which is not achievable using twoterminal memristors. For example, the conductance between a pair of floating electrodes (pre- and post-synaptic neurons) is varied by a factor of about ten by applying voltage pulses to modulatory terminals. In situ scanning probe microscopy, cryogenic charge transport measurements and device modelling reveal that the bias-induced motion of MoS2 defects drives resistive switching by dynamically varying Schottky barrier heights. Overall, the seamless integration of a memristor and transistor into one multi-terminal device could enable complex neuromorphic learning and the study of the physics of defect kinetics in two-dimensional materials.