Atomic origin of ultrafast resistance switching in nanoscale electrometallization cells
Atomic origin of ultrafast resistance switching in nanoscale electrometallization cells
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DOI：
10.1038/nmat4221
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发表时间：
2015-04-01
期刊：
影响因子：
41.2
通讯作者：
Strachan, Alejandro
中科院分区：
文献类型：
--
作者：
Onofrio, Nicolas;Guzman, David;Strachan, Alejandro
纳米级电阻开关电池通过连接两个电极的金属丝的电化学形成和断裂来工作，是后CMOS电子学中最有前途的器件之一。尽管它们很重要，但支配它们非凡特性的机制还没有完全被理解，特别是对于以超快速度运行的纳米设备，限制了我们评估这项技术的最终性能和可扩展性的能力。我们首次使用反应分子动力学对导电桥接电池的运行进行了原子模拟，并扩展了电荷平衡方法来描述电化学反应。这些模拟预测了在这些器件中观察到的超快开关，对于由铜活动电极和非晶态二氧化硅介质组成的器件，时间尺度从数百皮秒到几纳秒不等，并且其尺寸对应于它们的比例限制(横截面低于10 nm)。我们发现，单原子链桥通常是在器件运行过程中形成的，但它们是亚稳态的，寿命低于一纳秒。稳定细丝的形成涉及离子聚集成小的金属团簇，随后当它们连接到阴极时进行化学还原。与在更大的细胞中观察到的相反，纳米级的导电桥通常缺乏晶体有序。对开关过程的原子级机械理解为此类应用的材料优化提供了指导方针，对一系列设备的定量预测提供了对其最终规模和性能的洞察。
Nanoscale resistance-switching cells that operate via the electrochemical formation and disruption of metallic filaments that bridge two electrodes are among the most promising devices for post-CMOS electronics. Despite their importance, the mechanisms that govern their remarkable properties are not fully understood, especially for nanoscale devices operating at ultrafast rates, limiting our ability to assess the ultimate performance and scalability of this technology. We present the first atomistic simulations of the operation of conductive bridging cells using reactive molecular dynamics with a charge equilibration method extended to describe electrochemical reactions. The simulations predict the ultrafast switching observed in these devices, with timescales ranging from hundreds of picoseconds to a few nanoseconds for devices consisting of Cu active electrodes and amorphous silica dielectrics and with dimensions corresponding to their scaling limit (cross-sections below 10 nm). We find that single-atom-chain bridges often form during device operation but that they are metastable, with lifetimes below a nanosecond. The formation of stable filaments involves the aggregation of ions into small metallic clusters, followed by a progressive chemical reduction as they become connected to the cathode. Contrary to observations in larger cells, the nanoscale conductive bridges often lack crystalline order. An atomic-level mechanistic understanding of the switching process provides guidelines for materials optimization for such applications and the quantitative predictions over an ensemble of devices provide insight into their ultimate scaling and performance.