Low‐Operating‐Voltage Resistive Switching Memory Based on the Interlayer‐Spacing Regulation of MoSe₂

Abstract

The development of commercially available flexible and wearable devices requires low‐operating‐voltage circuit and resistive random access memory (RRAM). This paper reports the preparation and performances of low‐operating‐voltage RRAM based on the interlayer‐spacing regulation of MoSe2. Twine‐jumble‐like MoSe2 clusters were synthesized via hydrothermal method. The average interlayer spacing in the clusters is higher than the value for bulk MoSe2 by 9.969%. The layer count of the MoSe2 sample predicted according to the experimental value of in the Raman spectroscopy is 1.403 while it is 2 regarding the characteristic of A1g peak and the existence of B2g peak, which is inconsistent with the results of scanning electron microscope and transmission electron microscope. Calculation of van der Waals force reveals that the twine‐jumble‐like MoSe2 should not be considered as a bi‐layer (or few‐layer) crystal, but as a cluster consisting of a numerous monolayer crystals. Compared with the conventional nanosized MoSe2, the SET/RESET voltages of the RRAM device based on the monolayer MoSe2 clusters are decreased by 4–10 times while the switching ratio and endurance are increased by 2–40 and 2–10 times respectively, which is due to that the interstitial radius in the monolayer MoSe2 clusters is higher than that of a silver ion.

Ultralow-Power RRAM with a High Switching Ratio Based on the Large van der Waals Interstice Radius of TMDs

“…The lattice distortion δ can be calculated according to eqs S2, S4 and S5. Concerning the reported SET voltages and the calculated values of δ for TMDs, as shown in Figure a, it is found that δ/ d ( d is the spacing between the two S atom layers, while δ denotes the interlayer spacing variation for forming the Ag conductive filament) increases linearly with increasing V SET . When V SET is equal to 0.31 V, δ is decreased to 0.…”

“…According to the vdW interlayer spacing determined by experiments, the values of r g for SnS 2 nanosheets, SnS 2 flower-like microspheres (Figure S4), MoS 2 flower-like microspheres (Figure S5), MoS 2 thin films, MoSe 2 flower-like microspheres, MoSe 2 nanorods and WS 2 nanosheets with wide vdW interlayer spacings and those for bulk SnS 2 , MoS 2 , MoSe 2 and WS 2 with normal vdW interlayer spacings were calculated by using eq . Table S1 lists the calculated values of r g , while Table lists the SET voltage, SET power, switching ratio, and endurance of TMD-based RRAMs with different values of r g .…”

“…For TMD materials bound together by vdW forces, the weak binding force between the vdW layers enables control of their properties by adjusting the vdW interlayer spacing. Increasing the vdW interlayer spacing of TMDs can lead to an increase in the vdW interstice radius ( r g in Figure S2). Therefore, the weak interaction between the vdW layers of TMDs makes it possible to form metal conductive filament along the vdW interstice, as the interstice between the vdW layers has a higher size.…”

“…Graphene, − transitional-metal dichalcogenides (TMDs), − transition-metal carbides and nitrides (MXenes), hexagonal boron nitride (hBN) and semiconductor polymers , are two-dimensional (2D) storage materials discovered in recent years that can be used to fabricate not only rigid RRAM but also flexible RRAM. RRAM based on a 2D material storage layer − , shows better performance potential than that based on oxide materials. ,,,− The performance index of RRAM based on 2D materials developed in just over 10 years (solid blue dots − , in Figure S1) has caught up with that based on oxide materials (hollow violet dots ,,,− in Figure S1), which have been investigated for 60 years.…”

“…For 2D materials bound together by the van der Waals (vdW) force, the weak binding force between the vdW layers enables regulation of the material properties and device performance by adjusting the vdW interlayer spacing ( d F ). , By changing the hydrothermal process, Xie prepared a layered structure of MoS 2 with a vdW interlayer spacing 54% larger than that of the normal material. The MoS 2 with the widened vdW interlayer spacing showed good electrochemical properties, and the cathode current density reached 126.5 mA cm –2 at an overpotential of 300 mV (60 times higher than that of the normal MoS 2 ) .…”