Two-terminal floating-gate memory with van der Waals heterostructures for ultrahigh on/off ratio

TLDR

Conventional flash memory suffers from low reliability, high off‑state current, and thick rigid blocking oxides that limit vertical scaling. The study reports a two‑terminal floating‑gate memory fabricated from a monolayer MoS₂/h‑BN/graphene vertical stack. The device uses a single electrode to drive current through MoS₂ while charging and discharging a graphene floating gate via h‑BN tunnelling. The memory achieves an off‑state current of 10⁻¹⁴ A, yielding an on/off ratio over 10⁹—about 10³ times higher than other two‑terminal memories—and can stretch beyond 19 % for soft electronics.

Abstract

Abstract Concepts of non-volatile memory to replace conventional flash memory have suffered from low material reliability and high off-state current, and the use of a thick, rigid blocking oxide layer in flash memory further restricts vertical scale-up. Here, we report a two-terminal floating gate memory, tunnelling random access memory fabricated by a monolayer MoS 2 /h-BN/monolayer graphene vertical stack. Our device uses a two-terminal electrode for current flow in the MoS 2 channel and simultaneously for charging and discharging the graphene floating gate through the h-BN tunnelling barrier. By effective charge tunnelling through crystalline h-BN layer and storing charges in graphene layer, our memory device demonstrates an ultimately low off-state current of 10 −14 A, leading to ultrahigh on/off ratio over 10 9 , about ∼10 3 times higher than other two-terminal memories. Furthermore, the absence of thick, rigid blocking oxides enables high stretchability (>19%) which is useful for soft electronics.