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Memory technologies and applications implemented fully or partially using emerging 2D materials have attracted increasing interest in the research community in recent years. Their unique characteristics provide new possibilities for highly integrated circuits with superior performances and low power consumption, as well as special functionalities. Here, an overview of progress in 2D‐material‐based memory technologies and applications on the circuit level is presented. In the material growth and fabrication aspects, the advantages and disadvantages of various methods for producing large‐scale 2D memory devices are discussed. Reports on 2D‐material‐based integrated memory circuits, from conventional dynamic random‐access memory, static random‐access memory, and flash memory arrays, to emerging memristive crossbar structures, all the way to 3D monolithic stacking architecture, are systematically reviewed. Comparisons between experimental implementations and theoretical estimations for different integration architectures are given in terms of the critical parameters in 2D memory devices. Attempts to use 2D memory arrays for in‐memory computing applications, mostly on logic‐in‐memory and neuromorphic computing, are summarized here. Finally, challenges that impede the large‐scale applications of 2D‐material‐based memory are reviewed, and perspectives on possible approaches toward a more reliable system‐level fabrication are also given, hopefully shedding some light on future research.

 

From a fundamental science perspective, black phosphorus (BP) is a canonical example of a material that possesses fascinating surface and electronic properties. It has extraordinary in‐plane anisotropic electrical, optical, and vibrational states, as well as a tunable band gap. However, instability of the surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications. Early studies were limited by the degradation of black phosphorous surfaces in air. Recently, several robust strategies have been developed to mitigate these issues, and these novel developments can potentially allow researchers to exploit the extraordinary properties of this material and devices made out of it. Here, the fundamental chemistry of BP degradation and the tremendous progress made to address this issue are extensively reviewed. Device performances of encapsulated BP are also compared with nonencapsulated BP. In addition, BP possesses sensitive anisotropic photophysical surface properties such as excitons, surface plasmons/phonons, and topologically protected and Dirac semi‐metallic surface states. Ambient degradation as well as any passivation method used to protect the surface could affect the intrinsic surface properties of BP. These properties and the extent of their modifications by both the degradation and passivation are reviewed.

 

Memristive devices can offer dynamic behaviour, analogue programmability, and scaling and integration capabilities. As a result, they are of potential use in the development of information processing and storage devices for both conventional and unconventional computing paradigms. Their memristive switching processes originate mainly from the modulation of the number and position of structural defects or compositional impurities—what are commonly referred to as imperfections. While the underlying mechanisms and potential applications of memristors based on traditional bulk materials have been extensively studied, memristors based on van der Waals materials have only been considered more recently. Here we examine imperfection-enabled memristive switching in van der Waals materials. We explore how imperfections— together with the inherent physicochemical properties of the van der Waals materials—create different switching mechanisms, and thus provide a range of opportunities to engineer switching behaviour in memristive devices. We also discuss the challenges involved in terms of material selection, mechanism investigation and switching uniformity control, and consider the potential of van der Waals memristors in system-level implementations of efficient computing technologies.