Unipolar resistive switching of ZnO-single-wire memristors
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NANO EXPRESS
Open Access
Unipolar resistive switching of ZnO-single-wire memristors Yong Huang1,2, Ying Luo1, Zihan Shen1, Guoliang Yuan1 and Haibo Zeng1*
Abstract Well unipolar resistive switching (RS) behaviors were observed from Ag/ZnO single-microwire/Ag memristors. The reset voltages were larger than the set voltages, and all of them were less than 1 V. The resistance ratios of high-resistance state (HRS) to low-resistance state (LRS) reached 103. The bistable RS behaviors were entirely reversible and steady within 100 cycles. It was found that the dominant conduction mechanisms in LRS and HRS were ohmic behavior and space-charge-limited current (SCLC), respectively. Keywords: ZnO; Resistive random access memory (RRAM); Resistive switching (RS); Electrical properties
Background Resistive random access memory (RRAM) and memristor have attracted rapidly increasing attention due to their high-speed operation, high-density storage, and lowvoltage driving virtues for nonvolatile memory (NVM) applications [1,2]. Generally, a memristor is composed of a metal-insulator-metal (MIM) cell, where the NVM effect comes from their ability of reversible resistive switching (RS) between low-resistance state (LRS or RON) and highresistance state (HRS or ROFF) under voltage stimulus. Among the various candidate materials for RRAM and memristor, zinc oxide (ZnO) has promising advantages, such as facile synthesis, reversible and steady RS property, and low set and reset voltages [3-5]. Up to now, memristors based on ZnO thin films have been reported according to their RS behaviors from intrinsic defects (e.g., oxygen vacancies) and extrinsic impurities (e.g., Ag+ ions) [6-8]. However, several serious problems for memristors still exist. First of all, the RS mechanisms are still subjects of heated debate. Second, the operating voltages are usually too large and expected to be less than 1 V. Finally, the RS behavior in a single ZnO microwire has seldom been reported, but could have special applications due to its one-dimensional structure which include memristors, nanolasers, photodiodes, nanogenerators, gas * Correspondence: [email protected] 1 Institute of Optoelectronics & Nanomaterials (ION), School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China Full list of author information is available at the end of the article
sensors, acoustic resonators, piezoelectric gated diodes, etc. [5,9]. In this paper, we report on a ZnO single-wire memristor with low driving voltage and high stability as well as its interesting RS behaviors. Well unipolar RS properties were observed, including the set and reset voltages less than 1 V, resistance ratio as high as 103, and strong endurance stability within 100 cycles. Abnormally, the reset voltages are observed to be larger than the set voltages, which are contrary to most previous reports and are explained by the space-charge-limited current (SCLC).
Methods ZnO microwires were synthesized in a horizontal quartz tube furnace (6 cm
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