High-performance memristors based on AlN films have been demonstrated, which exhibit ultrafast ON/OFF switching times (≈85 ps for microdevices with waveguide) and relatively low switching current (≈15 μA for 50 nm devices). Physical characterizations are carried out to understand the device switching mechanism, and rationalize speed and energy performance. The formation of an Al-rich conduction channel through the AlN layer is revealed. The motion of positively charged nitrogen vacancies is likely responsible for the observed switching.

High-speed and low-energy nitride memristors

New chemical pathways are of fundamental interest for materials synthesis. Here, we report a novel surfactant-free, solution-phase, low-temperature route to crystalline, ultrasmall (∼2 nm) Cu3N nanoparticles via a one-step reaction between copper(II) methoxide and benzylamine. We propose a reaction mechanism for Cu3N formation based on the gas chromatography–mass spectrometry (GC–MS) analysis of the organic reaction byproducts. The reaction pathway involves reduction of the Cu(II) to Cu(I) by benzylamine, in situ generation of ammonia, and finally, the reaction between Cu(I) and ammonia to form Cu3N. We tested the Cu3N nanoparticles as an anode material for Li-ion batteries (LIBs). According to cyclic voltammetry, the Cu3N nanoparticles quickly undergo a phase transformation to Cu2O, but then stably deliver a capacity of ∼290 mAh/g at 1 A/g in the following 150 cycles.

Ultrasmall Cu3N Nanoparticles: Surfactant-Free Solution-Phase Synthesis, Nitridation Mechanism, and Application for Lithium Storage

Resistive random access memory (RRAM) devices are made by copper nitride films prepared by DC magnetron sputtering. After a forming process, the CuxN-based RRAM devices show bipolar character with low operation voltage and distinguishable resistance ratio. The fitting results for the electrical measurements and the conducting atomic force microscope (CAFM) analysis indicate that resistive switching mechanism is consistent with the formation and rupture of conducting filaments. Simultaneously, the distribution of conducting filaments measured by CAFM reveals a promising potential to fabricate high-density RRAM device by using this material. The mechanism of the formation of conducting filaments is discussed based on our results.

Resistive-switching behavior and mechanism in copper-nitride thin films prepared by DC magnetron sputtering

Using temperature-programmed desorption, supported by X-ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20-tetraphenyl-21H,23H-porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high-coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T-type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested.

Coverage‐ and Temperature‐Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111)

In this letter, the effect of the work function difference between various top electrodes (TE-Ni, W, Ti, and Al) and the Pt bottom electrode, ΔΦM, on the resistive switching (RS) of SiN thin films was investigated. The cells with W and Ti TEs showed stable RS, but others failed to show RS. In particular, the Ti TE exhibited low operating currents (~2 μA) and good retention properties (<; ~104 s at 85 °C). On the basis of the analysis of conduction mechanisms, it is found that stable RS of SiN films might be strongly related to the activation energy of traps induced by ΔΦM. Thus, the RS properties of the SiN films can be improved by engineering ΔΦM without additional processes.

Effect of Work Function Difference Between Top and Bottom Electrodes on the Resistive Switching Properties of SiN Films

Copper nitride film prepared by plasma-immersion ion implantation (PIII) is demonstrated to exhibit reversible resistance variance character. By forming a gradually distributed nitrogen concentration in the Cu-nitride film, the nitride-based memory devices show bipolar nature with a low operation voltage, forming-free characteristics and a distinguishable resistance ratio. The bipolar switching behavior is attributed to the formation and rupture of conductive filaments within a cycle, which is confirmed by spreading-resistance images of a conducting atomic force microscope. Based on X-ray photoelectron spectroscopy (XPS) analysis, semiconducting Cu3N phase and metallic Cu4N phase coexist in the copper nitride film and local conducting filaments might be formed by interconnection of the metallic phases by migration of Cu+ ions under a bias voltage.

Reproducible resistive‐switching behavior in copper‐nitride thin film prepared by plasma‐immersion ion implantation

The invention belongs to the technical field of non-volatile memories, particularly to a metal nitride material with resistance change nature and the application thereof. The metal nitride is MxN, M is Mn, Fe, Co, Ni, Cu, Zn, Al, Si, Ga, In, Sc or Y, or the alloy of any two or more elements in the metal material, x is more than or equal to 0.2 and less than or equal to 4, and the metal nitride can be prepared through a plurality of conventional film preparation methods, and has resistance change performance through the control to the nitrogen content in the film. The material can serve as an intermediate resistance change layer and is applied to an RRAM component. The RRAM component comprises a lower electrode layer, a resistance change metal nitride layer arranged on the lower electrode and an upper electrode layer arranged on the resistance change layer. The sandwich structure is highly compatible with a traditional integrated circuit process. The invention provides a novel direction for the selection of resistance change material, and is beneficial to the development of the RRAM memory to low cost and high performance.

Metal nitride with resistance change nature and application thereof

The invention belongs to the technical field of variable resistance random access memories and particularly relates to a preparation method of variable resistance metal nitride materials. The preparation method comprises the following steps of: generating nitrogen plasmas in a low vacuum cavity; and injecting the plasmas by applying negative bias voltage on metal film materials, thereby forming a metal nitride film on the surface of a metal layer. Prepared metal nitride can be used as middle double resistance layer materials to be applied to a component of the variable resistance random access memory (Resistance Random Access Memory, RRAM for short), and the device performance is optimized by controlling the concentration and the distribution of the nitrogen ion in the film.

Wei Zhu

Papers

Resistive-switching behavior and mechanism in copper-nitride thin films prepared by DC magnetron sputtering

Reproducible resistive‐switching behavior in copper‐nitride thin film prepared by plasma‐immersion ion implantation

Metal nitride with resistance change nature and application thereof

Preparation method of variable resistance metal nitride materials

Preparation method of copper nitride resistive material for high-density resistive random access memory