Direct Observation of a Carbon Filament in Water-Resistant Organic Memory

Abstract

The memory for the Internet of Things (IoT) requires versatile characteristics such as flexibility, wearability, and stability in outdoor environments. Resistive random access memory (RRAM) to harness a simple structure and organic material with good flexibility can be an attractive candidate for IoT memory. However, its solution-oriented process and unclear switching mechanism are critical problems. Here we demonstrate iCVD polymer-intercalated RRAM (i-RRAM). i-RRAM exhibits robust flexibility and versatile wearability on any substrate. Stable operation of i-RRAM, even in water, is demonstrated, which is the first experimental presentation of water-resistant organic memory without any waterproof protection package. Moreover, the direct observation of a carbon filament is also reported for the first time using transmission electron microscopy, which puts an end to the controversy surrounding the switching mechanism. Therefore, reproducibility is feasible through comprehensive modeling. Furthermore, a carbon filament is superior to a metal filament in terms of the design window and selection of the electrode material. These results suggest an alternative to solve the critical issues of organic RRAM and an optimized memory type suitable for the IoT era.

Foldable and Disposable Memory on Paper

“…The nanopaper has a root mean square (RMS) surface roughness on the nanometer scale and high foldability30313233. An organic layer, serving as the resistive switching layer (RSL), is deposited by initiated chemical vapor deposition (iCVD), which is an all-dry vapor-phase process that does not require any solvent34. Fabrication processes involving solvents lead to safety and health considerations, which can limit biocompatible applications.…”

“…Its fundamental performance metrics including program/erase/read operations and endurance against ordinary bending cycles were assessed along with the foldability and disposability characteristics. In addition, the switching mechanism of the fabricated device corresponds to the filamentary conduction, where details are provided in Supplementary Information (refer to Supplementary Information S3)34.…”

Nonvolatile Memory Device Based on Bipolar and Unipolar Resistive Switching in Bio‐Organic Aloe Polysaccharides Thin Film

“…The redox process is electric field driven, as the established conduction path can only be dissolved when a reversed bias is applied during the RESET operation. Electrochemical formation and dissolution of the filamentary conduction path have been observed directly in several inorganic and organic devices, but such observation is still not applicable for bio‐organic devices. Nevertheless, naturally occurring bio‐organic materials have properties that favor ionic conduction, rendering their exotic application in a variety of bioelectronics.…”

“…This result shows that resistive switching is confined only to a localized region within the polysaccharides film just like the formation of metallic filaments. The formation and annihilation of carbon‐rich nanostructures (e.g., filaments, nanowires, or tubules) with improved electrical conductivity are feasible under the effect of high‐bias Joule heating . In general, carbon atoms in an amorphous carbon film hybridize their outermost s and p orbitals into sp 3 and sp 2 hybrids to form σ‐ and π‐bonds, respectively .…”

Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device Applications

“…a) Schematic structure and V T shift mechanism of a transistor‐type photomemory . b) Cross‐sectional TEM image of carbon filaments in pEGDMA RRAM and c) its IV characteristics before and after a submerged time of 27 h . d) IV characteristics of pV3D3 RRAM .…”