Large‐Scale, Low‐Power Nonvolatile Memory Based on Few‐Layer MoS₂ and Ultrathin Polymer Dielectrics

Abstract

With the advent of artificial intelligence and the Internet of Things, demand has grown for flexible, low‐power, high‐density nonvolatile memory capable of handling vast amounts of information. Ultrathin‐layered 2D semiconductor materials such as molybdenum disulfide (MoS2) have considerable potential for flexible electronic device applications because of their unique physical properties. However, development of flexible MoS2‐based flash memory is challenging, as there is a lack of flexible dielectric materials with sufficient insulating properties for use in flash memory devices with dielectric bilayers. Here, large‐scale, low‐power nonvolatile memory is realized based on a chemical vapor deposition (CVD)‐grown millimeter‐scale few‐layer MoS2 semiconductor channel and polymer dielectrics prepared via an initiated CVD (iCVD) process. Using the outstanding insulating properties and solvent‐free nature of iCVD, fabricated memory devices with a tunable memory window, a high on/off ratio (≈106), low operating voltages (≈13 V), stable retention times exceeding 105 s with a possible extrapolated duration of years, and cycling endurance exceeding 1500 cycles are demonstrated. Owing to these characteristics, these devices distinctly outperform previously reported MoS2‐based memory devices. Leveraging the inherent mechanical flexibility of both ultrathin polymer dielectrics and MoS2, this work is a step toward realization of large‐scale, low‐power, flexible MoS2‐based flash memory.

Nanoscale control by chemically vapour-deposited polymers

“…The ultrasmooth, ultrathin (3-15 nm), flexible, and crosslinked organosilicon layer, poly(2,4,6trivinyl-2,4,6-trimethyl cyclotrisiloxane) (PV3D3, dielectric constant, k~2.2), has been integrated into devices 80,81 , including 3D stacking of organic thin film transistors (TFTs) 82 . The PV3D3 serves as an electret layer when coupled with an ultrathin (20 nm) crosslinked iCVD poly(1,4butanediol diacrylate) (PBDDA) film as blocking dielectric (Fig.…”

“…86 For higher k dielectrics, the iCVD copolymerization of 2-cyanoethyl acrylate and the crosslinker DEGDVE achieved k~6.2. 81 Extension of the iCVD method for ultrathin, flexible, and high-k hybrid organic-inorganic layers for fabricating low-leakage current TFTs. 87,88 The hybrids were obtained by adding of trimethyl alumina or tetrakis-dimethyl-amino-zirconium reactant vapors along HEMA and the TBPO initiator.…”

Emerging Opportunities for Electrostatic Control in Atomically Thin Devices

“…Inset shows the switching endurance for over 1500 cycles. Adapted with permission under a Creative Commons CC-BY License from ref . Copyright 2019 John Wiley and Sons.…”

“…Due to opportunities for simplified processing, researchers have also explored atomically thin nonvolatile memory where nanoscale metal films are evaporated and annealed to obtain metal islands or nanoparticles that act as floating gates. − For example, Wang et al determined that Au nanoparticles, compared to Co, Ag, and Al, provided superior floating-gate performance with a voltage hysteresis of 10 V, switching ratio of 10 6 , and retention for over 2000 s in MoS 2 -based devices . Replacing the metal control gate with an indium tin oxide (ITO) gate, Gong et al demonstrated voltage hysteresis of 10 V with a switching ratio > 10 3 , where a laser pulse could promote carriers to the floating gate .…”

“…Replacing the metal control gate with an indium tin oxide (ITO) gate, Gong et al demonstrated voltage hysteresis of 10 V with a switching ratio > 10 3 , where a laser pulse could promote carriers to the floating gate . With a motivation for fully flexible devices, Yang et al investigated polymers for the blocking and tunneling dielectrics . Using exfoliated MoS 2 flakes and Au nanoparticles, these polymer dielectric devices achieved a voltage hysteresis <6 V, switching ratios of 10 6 , and endurance over 1500 cycles (Figure e) …”