Bias Polarity‐Induced Transformation of Point Contact Resistive Switching Memory from Single Transparent Conductive Metal Oxide Layer

Abstract

including the migration of oxygen ions and oxygen defi ciencies. Furthermore, nanoscale devices using the TCO layer as the memristive material with repeatable and robust RS behavior were further developed and demonstrated. We believe the fi ndings would break the understanding of the "simplest" ReRAM MIM confi guration to realize the ReRAM with a "point contact" concept for the highest stacking density for development of 3D ReRAM application.Migration/interexchange of oxygen ions/oxygen vacancies triggered by electrical fi elds in some metal oxides have been theoretically calculated and reported. [ 12,13 ] A calculated electric fi eld of 80 V cm −1 was applied to trigger migration of oxygen vacancies in NiO fi lm [ 13 ] whereas activation energy of 0.05 eV for oxygen vacancies hopping in the HfO 2 was evaluated. [ 12 ] An example of how to transform conductive into RS behaviors was applied on the ITO layer in an ambient condition as shown in Figure 1 a. A two-probe confi guration was taken to directly obtain the RS behavior from the ITO layer as shown in inset in Figure 1 a in order to achieve the migration of oxygen ions in the TCO layers by controlling the electrical fi eld. Note that one W-probe was directly contacted with the TCO thin fi lm and another probe was contacted to the platinum (Pt) electrode, for which the Pt electrode was utilized to prevent the occurrence of the T CàRS in both sides of probes. First, an "Initiation" process, namely a large enough DC bias is needed to trigger the T CàRS characteristics. In the initiation process, the current linearly increases as the bias increases, indicating an ohmic behavior when the W probe contacting with the ITO layer. Once the bias > 5 V, an abruptly drop of the current from 100 mA into tens of µA was achieved, resulting in the transformation of the resistance state from conductive to high resistance states (HRS). A negatively biased SET process was applied to switch the resistance from HRS to low resistance state (LRS), as indicted by the red-triangle curve (Figure 1 a) while the blue-circle curve was obtained as positively biased RESET process was applied to switch the resistance from LRS to HRS. These distinctly resistive changes at different polarities in the ITO layer are called bipolar resistive switching behavior, which could be recognized as digital signals in memory application. Endurance test could be stably obtained over 100 cycles at SET and RESET biases within −1.1 and +1.0 V, respectively, as shown in Figure 1 b. To exclude the infl uence of oxygen under an ambient condition, transformation of RS from conductive behavior on the ITO layer was intentionally conducted in an ultrahigh vacuum (UHV) environment with a pressure of ≈10 −9 Torr as shown in Figure 1 c. Note that initiation, SET and RESET biases are relatively smaller than that of the case in air. The initiation Multibit storage function, fast programming speed, low power consumption, high scalability, and easy fabrication process make the resistive switching random access memory (ReRAM)...

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Efficient Resistive Switching and Spike Rate Dependent Plasticity in a New CuCrO2 Memristor for Plausible Neuromorphic Systems

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