There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

A memristor is a two-terminal electronic device whose conductance can be precisely modulated by charge or flux through it. Here we experimentally demonstrate a nanoscale silicon-based memristor device and show that a hybrid system composed of complementary metal−oxide semiconductor neurons and memristor synapses can support important synaptic functions such as spike timing dependent plasticity. Using memristors as synapses in neuromorphic circuits can potentially offer both high connectivity and high density required for efficient computing.

/pdf/nanoscale-memristor-device-as-synapse-in-neuromorphic-1sl2njhdyu.pdf

Nanoscale Memristor Device as Synapse in Neuromorphic Systems

A selector for a bipolar resistive random access memory and a method for fabricating the selector are provided. The method includes: providing a substrate; forming a lower electrode on the substrate, where the lower electrode is made of a metal, and the metal is made up of metal atoms which diffuse under an annealing condition of below 400° C.; forming a first metal oxide layer on the lower electrode; performing an annealing process on the first metal oxide layer to make the metal atoms in the lower electrode diffuse into the first metal oxide layer to form a first metal oxide layer doped with metal atoms; forming a second metal oxide layer on the first metal oxide layer doped with metal atoms; forming an upper electrode layer on the second metal oxide layer; and patterning the upper electrode layer to form an upper electrode.

Selection device for use in bipolar resistive memory and manufacturing method therefor

The invention discloses a phosphine-nitrogen ligand with multiple chiral centers as well as a synthesis method and application thereof. The ligand has the axial chirality of a biaryl skeleton and thecentral chirality of chiral amine. The chiral ligand is synthesized from commercialized easily available raw materials through simple five-step reaction, and the finally obtained diastereoisomer product can be separated only through simple column chromatography or re-crystallization. The chiral phosphine nitrogen ligand synthesized by the method can catalyze asymmetric three-component coupling reaction of terminal alkyne, aldehyde and amine, so that the chiral propargyl amine compound with high optical activity is efficiently prepared.

Phosphine nitrogen ligands with various chiral centers as well as synthesis method and application thereof

We herein present an asymmetric I–V characteristics PNPN selector for bipolar resistive switching (RS) memory crossbar array application. Negative curve of the PNPN selector with high current density was demonstrated, which is analogous to threshold switching (TS). Moreover, latch-up voltage is designable by tuning the p/n-region doping and length. On the other hand, the positive behavior is designed to nonlinear curve by barrier lowering mechanism. The conceptual framework to suppress the sneak-current was demonstrated by integrating a bipolar RS memory element with the PNPN selector, indicating that the PNPN selector has good potential for future high-density cross-point application.

A novel PNPN bipolar selector for RRAM array application

Provided are a self-gating resistive storage device and a method for fabrication thereof; said self-gating resistive storage device comprises: lower electrodes; insulating dielectric layers arranged perpendicular to, and intersecting with, the lower electrodes to form a stacked structure, said stacked structure being provided with a vertical trench; a gating layer grown on the lower electrodes by means of self-alignment technique, the interlayer leakage channel running through the gating layer being isolated via the insulating dielectric layers; a resistance transition layer arranged in the vertical trench and connected to the insulating dielectric layers and the gating layer; and an upper electrode arranged in the resistance transition layer. In the storage device provided by the described technical solution, the gating layer is grown on the lower electrodes by means of self-alignment technique, such that the interlayer leakage channel running through the gating layer is isolated via the insulating dielectric layers; thus leakage between the upper and lower word lines through the gating layer is prevented, solving the technical problem in the prior art of leakage between the upper and lower word lines in a self-gating resistive storage device, and improving the reliability of the device.

Self-gating resistive storage device having resistance transition layer in vertical trench in stacked structure of insulating dielectric layers and electrodes

Conductive bridge random access memory is considered to be a promising candidate or complementary component to the traditional charge based memory. In-depth understanding of the failure behavior is essential for performance optimization. In this work, the failure mechanisms of endurance and retention of HfO 2 -based cell were studied in a 1 kb array. The degradation of high resistance state was found to exist in the majority cases of endurance failure (stuck at low resistance state). Based on high resolution transmission electron microscopy analysis, the copper accumulation in the filament was found to be the dominant reason behind the endurance failure. The mechanism of retention failure was found related with the lateral diffusion of copper species from the filament to its surrounding (or to the tunneling gap from the filament tip to counter electrode). The retention of high resistance state was degraded with the switching cycle, whereas that of low resistance state was improved. This work provides a basic understanding on the failure mechanism of electrochemical resistive switching memory.

Qi Liu

Papers

Selection device for use in bipolar resistive memory and manufacturing method therefor

Phosphine nitrogen ligands with various chiral centers as well as synthesis method and application thereof

A novel PNPN bipolar selector for RRAM array application

Self-gating resistive storage device having resistance transition layer in vertical trench in stacked structure of insulating dielectric layers and electrodes

A probe of reliability issues of oxide electrolyte based CBRAM