For example, a semi-floating-gate memory with quasi-nonvolatile behavior was proposed 6, 9, 20, in which charges can be directly injected into the floating gate through a p-n junction instead of the FN tunneling, and thus it features an operation voltage of a few volts. New strategies with novel device structures are urgently needed to break the limitation of FN tunneling mechanism. Low-voltage ultrafast nonvolatile memory is still a great challenge. Unfortunately, a high operation voltage (tens of volts) is demanded in these devices due to the FN tunneling mechanism, which will consume more energy and restrict their compatibility in complementary-metal-oxide-semiconductor (CMOS). For floating-gate memory, very recent investigations have demonstrated that the atomically sharp interface of two-dimensional (2D) materials facilitates the Fowler–Nordheim (FN) tunneling of charges through the tunneling layer, demonstrating a nanosecond operation speed 18, 19. However, the relatively large cycle-to-cycle and device-to-device variation of memristors still limit their practical application in memory. In the past decade, memristors, including nonvolatile resistive switching (RS) and volatile threshold switching (TS) based on filamentary switching 12, 13, 14, 15, 16, 17, have attracted wide attention due to their high operation speed and high integration density. Revolutionary memory technologies with ultrahigh speed, ultralong retention, ultrahigh capacity, and ultralow energy consumption based on new principles, new materials, and new structures are highly demanded 4, 6, 7, 8, 9, 10, 11. Current mainstream memory based on silicon technology is suffering unprecedented challenges including slow operation speed, limited storage capacity, and high energy consumption 2, 3, 4, 5, 6. Nowadays, with the advent of the big data era, huge amounts of data are created annually, urgently requiring high-speed and low-energy processing and storage 2. The rapid development of memory technologies including random-access memory and flash memory are indispensable for the success of information age in the past decades 1. These results demonstrate a new strategy to develop next-generation high-speed low-energy nonvolatile memory. The high operation speed and low voltage endow the device with an ultralow energy consumption of 10 fJ. The volatile threshold switching characteristic of graphdiyne oxide allows the direct charge injection from control gate to floating gate by applying a nanosecond voltage pulse (20 ns) with low magnitude (2 V), and restricts the injected charges in floating gate for a long-term retention (10 years) after the pulse. Here we propose a floating-gate memory with a structure of MoS 2/hBN/MoS 2/graphdiyne oxide/WSe 2, in which a threshold switching layer, graphdiyne oxide, instead of a dielectric blocking layer in conventional floating-gate memories, is used to connect the floating gate and control gate. It is still a great challenge to realize ultrafast nonvolatile storage with low operation voltage. Although a breakthrough in ultrafast floating-gate memory has been achieved very recently, it still suffers a high operation voltage (tens of volts) due to the Fowler–Nordheim tunnelling mechanism. The explosion in demand for massive data processing and storage requires revolutionary memory technologies featuring ultrahigh speed, ultralong retention, ultrahigh capacity and ultralow energy consumption.
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