Thinnest Nonvolatile Memory Based on Monolayer h‐BN

Abstract

Abstract2D materials have attracted much interest over the past decade in nanoelectronics. However, it was believed that the atomically thin layered materials are not able to show memristive effect in vertically stacked structure, until the recent discovery of monolayer transition metal dichalcogenide (TMD) atomristors, overcoming the scaling limit to sub‐nanometer. Herein, the nonvolatile resistance switching (NVRS) phenomenon in monolayer hexagonal boron nitride (h‐BN), a typical 2D insulator, is reported. The h‐BN atomristors are studied using different electrodes and structures, featuring forming‐free switching in both unipolar and bipolar operations, with large on/off ratio (up to 107). Moreover, fast switching speed (<15 ns) is demonstrated via pulse operation. Compared with monolayer TMDs, the one‐atom‐thin h‐BN sheet reduces the vertical scaling to ≈0.33 nm, representing a record thickness for memory materials. Simulation results based on ab‐initio method reveal that substitution of metal ions into h‐BN vacancies during electrical switching is a likely mechanism. The existence of NVRS in monolayer h‐BN indicates fruitful interactions between defects, metal ions and interfaces, and can advance emerging applications on ultrathin flexible memory, printed electronics, neuromorphic computing, and radio frequency switches.

A generic method to control hysteresis and memory effect in Van der Waals hybrids

“…We find a very low cycle to cycle variability in the memory ratio, defined as the ratio of the on and off state current, demonstrating the reliability of these non-volatile memory devices (inset of figure 3(d)). Furthermore, the memory ratio in our devices, which can be as high as 10 8 , is comparable to state of the art sensors fabricated with two-dimensional materials, that have reported in literature (Supplementary section C.2) [52][53][54][55][56][57][58][59]. Additionally, the low bias requirements and program state current value makes the device power efficient with an observed power dissipation of ≈10pW in the program state in our MoS 2 based memory devices [51].…”

2D Layered Materials for Memristive and Neuromorphic Applications

“…This issue could be surmounted by the use of insulating h-BN [117] as active layer. By using CVD-synthesized monolayer h-BN, Wu et al fabricated memristive devices with the thinnest active layer (≈0.33 nm) and observed similar switching performance [113] with forming free feature (Figure 5c,d). [118] By pushing the thickness of active layer to atomic limit, Ge et al reported the first atomristor based on monolayer TMDs (i.e., MoS 2 , MoSe 2 , WS 2 , WSe 2 ).…”

“…Similar to the TMOs-based memristive devices, other ions migration, for example, B 3+ , N 3− and O 2− , in 2D layered materials have been proposed to account for the growth and rupture of filaments in vertical memristive devices; [57,60,80,109,112,113,129] It is well known that ions migration in conventional memristive devices causes the formation of filaments, while electricfield-induced S 2− migration in MoS 2 based planar structure memristive devices leads to the movement of grain boundaries and gives rise to resistive switching. Similar to the TMOs-based memristive devices, other ions migration, for example, B 3+ , N 3− and O 2− , in 2D layered materials have been proposed to account for the growth and rupture of filaments in vertical memristive devices; [57,60,80,109,112,113,129] It is well known that ions migration in conventional memristive devices causes the formation of filaments, while electricfield-induced S 2− migration in MoS 2 based planar structure memristive devices leads to the movement of grain boundaries and gives rise to resistive switching.…”

Ultrasonic‐Ball Milling: A Novel Strategy to Prepare Large‐Size Ultrathin 2D Materials

“…In Figure 3e, the Raman peak at 1363.8 cm −1 of BNNS has a bathochromic‐shift compared to that of bulk h‐BN, which is due to the influence of the stretching vibration between the nanosheet and the Si/SiO 2 substrate used in the test on the E 2g vibration of BNNS. [ 30,31 ] As shown in Figure 3f, the Raman spectrum of graphene includes the emerging D band and D' band at ≈1350 and 1620 cm −1 , which are attributed to the structural and edge defects caused by the disordered vibration of graphene. Meanwhile, the Raman spectrum of the obtained graphene demonstrates an I D / I G ratio of 0.28, which is much smaller than that of chemically or thermally reduced GO (≈1.1−1.5) and electrochemically exfoliated graphene (0.4) in acidic solution, [ 32 ] indicating a smaller degree of defects in the as‐obtained graphene.…”