Rational Design on Controllable Cation Injection with Improved Conductive-Bridge Random Access Memory by Glancing Angle Deposition Technology toward Neuromorphic Application

Abstract

A conductive-bridge random access memory (CBRAM) has been considered a promising candidate for the next-generation nonvolatile memory technology because of its excellent performance, for which the resistive switching behavior depends on the formation/dissolution of conducting filaments in an electrolyte layer originated by the cation injection from the active electrode with electrochemical reactions. Typically, the controllability of cations into the electrolyte layer is a main issue, leading to stable switching reliability. In this work, an architecture combining spike-shaped Ag electrodes created by Al2O3 nanopillar arrays as a physical diffusion barrier by glancing angle deposition technology was proposed to localize Ag cation injection for the formation of controllable filaments inside TiO x as the switching layer. Interestingly, the dimension of the Ag plugs defined by the topography of Al2O3 nanopillar arrays can control Ag cation injection to influence the dimensionality of conductive filaments. Compared to the typical planar-Ag/TiO x /Pt device, the spiked-Ag/Al2O3 nanopillar arrays/TiO x /Pt device shows improvement of endurance and voltage disturbance. With enhanced multilevel characteristics, the spiked active-metal-based CBRAM device can be expected to serve as an analogue synapse for neuromorphic applications.

HfOx-Based Conductive Bridge Random Access Memory with Al2O3 Sandglass Nanostructures via Glancing Angle Deposition Technology toward Neuromorphic Applications

“…Graphene has also been reported to serve as a barrier to confine cation injection. Zhao et al developed a nanopore graphene layer-inserted CBRAM, showing that the cation (Cu or Ag) can localizely inject into an insulating layer (HfO 2 or SiO 2 ) by the nanohole of graphene, resulting in confined CF formation. , In our previous study, we proved that insertion of the Al 2 O 3 nanopillar barrier layer into the TiON-based CBRAM can prevent the overmigration of Ag atoms, thus improving the endurance and multilevel cell (MLC) characteristics …”

“…22,23 In our previous study, we proved that insertion of the Al 2 O 3 nanopillar barrier layer into the TiON-based CBRAM can prevent the overmigration of Ag atoms, thus improving the endurance and multilevel cell (MLC) characteristics. 24 In this regard, the confinement of Cu and Te CFs in HfO xbased CBRAM by Al 2 O 3 sandglass nanostructures (SGNSs) via glancing angle deposition technology (GLAD) 25−28 to improve the resistive switching and synaptic properties was demonstrated. The coverage and spacing of the Al 2 O 3 nanostructures can be controlled by the GLAD with specific deposition angles.…”

Effective Conduction Path of a C60 Chain in a Nanogap Electrode

“…When an electrical bias is applied, current is induced in the material, and its path is deformed. The deformed material along the current path can be observed by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) imaging. ,− In addition, the deformed material trace can be spatially mapped using Raman spectroscopy . For conductive media at the single-molecule scale, TEM images provide a direct visualization of the conductive channel, such as metallic atoms bridging the gap between two metallic contacts or a fullerene dimer within the gap .…”

Ultralow Set Voltage and Enhanced Switching Reliability for Resistive Random-Access Memory Enabled by an Electrodeposited Nanocone Array

“…Resistive random-access memory (RRAM) has been intensely investigated over the past 20 years due to its excellent application potential as a next-generation memory technology and neuromorphic computing. − However, the significant hurdle for industrial application is the spatial and temporal fluctuation of the switching voltage and resistance states due to the stochastic nature of ion migration and overinjection of ion species during the resistive switching process. − To solve this crucial issue, numerous attempts have been made to control the ion migration process. These strategies fall into three categories: (1) concentration of the electric field, ,,− (2) physical confinement of the ion migration path, ,− and (3) a chemical interaction between the inserted particle and switching medium to localize the ion migration process. ,, The corresponding references on the strategy categories, methods, compatibilities, performances, and characteristics are comprehensively summarized in Table . In comparison with other methods, manipulating electric fields in switching media has been the most popular way to overcome instability. ,,− ,, …”