A Single Nanoscale Junction with Programmable Multilevel Memory

Abstract

Nanoscale devices that are sensitive to measurement history enable memory applications, and memristors are currently under intense investigation for robustness and functionality. Here we describe the fabrication and performance of a memristor-like device that is comprised of a single TiO2 nanowire in contact with Au electrodes, demonstrating both high sensitivity to electrical stimuli and high levels of control. Through an electroforming process, a population of charged dopants is created at the interface between the wire and electrode that can be manipulated to demonstrate a range of device and memristor characteristics. In contrast to conventional two-terminal memristors, our device is essentially a diode that exhibits memristance in the forward bias direction. The device is easily reset to the off state by a single voltage pulse and can be incremented to provide a range of controllable conductance states in the forward direction. Electrochemical modification of the Schottky barrier at the electrodes is proposed as an underlying mechanism, and six-level memory operations are demonstrated on a single nanowire.Transition metal oxides are an emerging candidate material for the realization of non-volatile, low power memory devices for handheld and portable electronics.1, 2 Non-volatile memories that retain encoded information without power consumption would greatly enhance battery performance for all mobile platform technologies. 3 Recent devices based on transition metal oxides display many characteristics required for the next generation of resistive switching based random access memory (RRAM) technologies. 4-9 TiO2

Recent Developments and Perspectives for Memristive Devices Based on Metal Oxide Nanowires

“…[161] Since the memristor demonstration by Strukov et al [2] in 2008, TiO 2 has attracted great attention for the realization of memristive devices and several physical mechanisms of switching were reported in TiO 2 films. [161] Since the memristor demonstration by Strukov et al [2] in 2008, TiO 2 has attracted great attention for the realization of memristive devices and several physical mechanisms of switching were reported in TiO 2 films.…”

Photonic Synapses for Ultrahigh‐Speed Neuromorphic Computing

“…Initially, a high voltage of about 10 V is needed to activate the Au/TiO 2 /Au device. The magnitude of charge injection into the TiO 2 nanowire is adjusted by the population of oxygen vacancies at the Au/TiO 2 interface since the existence of oxygen vacancies can lower the tunneling barrier . The device presents a memristive diode‐like I – V characteristics.…”

Multilevel resistance in ZnO nanowire memristors enabled by hydrogen annealing treatment

“…This behavior contrasts with typical memristors, for which it known the conductance continuously increases during consecutive positive voltage sweeps. 2,3,7,12,16,[22][23][24]32 In that case, the increase in conductance is due to the progressive diffusion of mobile oxygen vacancies across the device under the influence of the applied field. 24 The measured I-V characteristics of the HAT ZnO NW device, however, exhibit decreasing conductance as the voltage sweeps are repeated, demonstrating that oxygen vacancies and their associated conduction electrons are trapped at a-ZnO interfacial layer formed between Au contact metal and ZnO NW.…”

“…22 Binary metal memristors oxides such as TiO 2 , NiO, and CuO have been considered as materials of great interests due to their rapid speed of resistive switching, high storage density, thermal/chemical stability and compatibility with CMOS circuits. [23][24][25][26] Among these, the properties of ZnO have attracted particular interest, due to its wide bandgap, adjustable doping and potential in application in the areas of photodiodes, piezoelectric devices and solar cells. [27][28][29] Many researchers have investigated the memristive behavior of ZnO in various structural motifs, [30][31][32][33] and from which it has been established that the drifts of oxygen ions (or oxygen vacancies) induced by surface treatment can enhance resistive switching in ZnO.…”