Bipolar resistive switching characteristics in CuO/ZnO bilayer structure

Abstract

Resistive switching characteristics in Cu/ZnO/AZO (Al-doped ZnO) were investigated. Reproducible bipolar resistance switching properties were observed in the single oxide layer (SL)-based device. To improve the switching performance, a CuO–ZnO bilayer (BL) was used to form a Cu/CuO/ZnO/AZO structure. RS characteristics such as retention time, endurance, variations of threshold voltage as well as distribution of resistance were investigated. The results demonstrated that the BL devices exhibit more excellent switching performance than SL devices. The conduction mechanisms of high and low resistance states can be explained by trap-controlled space charge limited current (SCLC) and Ohmic's Law, respectively. The CuO layer is proposed as a “reservoir” of oxygen ions in set process and acting as an oxygen ions “supplier” in reset process, which plays a critical role in recovery/rupture of filament paths and greatly improves the switching characteristics of the device.

CuO/ZnO memristors via oxygen or metal migration controlled by electrodes

“…The CuO film, acting as an oxygen reservoir in set process and supplier in reset process, can switch the device more efficiently and completely. 10 For ACZP structure, the RS mechanism can be reasonably explained by the universal ECM mode. 1,9 It is generally recognized that the Ag electrode is an active component in filament formation for electrochemical memory cells.…”

“…As for PCZP structure, it is known that oxygen vacancies exist in the ZnO thin film naturally. 10,16 When positive bias was applied on the Pt top electrode, the negatively charged oxygen ions would move to the CuO layer, so the oxygen vacancies in the ZnO film increase and form the filament path to activate the resistance switching to LRS, as shown in Fig. 4(a).…”

“…[3][4][5][6][7][8] And many explanations of the switching mechanisms has been proposed recently. [9][10][11] However, practical application of large-scale high-performance RRAM arrays and architectures still face significant challenges. As a set of performance criterions, e.g., switching speed, power consumption, memory window, cycling endurance and retention time, need to be acquired in the same device system.…”

“…Recent researches about RRAM devices based on bilayer oxide films indicate they may provide better performance over single-layer based devices. 8,10,[12][13][14][15] In addition, using bilayer materials as the switching media makes the role of each layer to be designed for a specific function during switching, thus offering large degrees of freedom for device optimization compared to usual methods of trying to get several functionalities in a single layer.…”

Superior unipolar resistive switching in stacked ZrOx/ZrO2/ZrOx structure

“…Different slopes of the fitting-lines correspond to different conduction mechanisms of the carriers in the single-layer 25% ZrO x , 33% ZrO 2 and the ZrO 2 stack films in a LRS and a HRS. The current slopes (log I) versus voltage (log V) plots in a LRS were around one, which indicates that the LRS was dominated by Ohmic conduction mechanism 25,26 for the three types of ZrO 2 RRAM. Two slopes (1.12 and 1.96) appeared in the HRS of the 33% ZrO 2 films at low and high voltages, respectively.…”