Faradaic currents and ion transfer numbers in electrochemical atomic switches

电阻开关的操作机制，即金属丝的形成和湮灭，被理解为基于固体电解质材料中的金属原子（离子）的氧化和还原。然而，在开关操作中的各种现象，如金属离子在材料中的迁移，在固体电解质和金属电极之间的界面处的氧化和还原过程，尚未在原子水平上揭示。这些基本的理解是必不可少的澄清缩小实际纳米器件的最终物理限制。此外，在将这些全新的器件引入当今的半导体电路之前，应先建立电阻开关的物理特性。由于其工作机理与半导体器件有很大的不同，因此还需要开发新的分析方法和计算模型。本项目从离子导体和电极材料、器件结构、形成和工作条件等方面研究了金属离子的离子迁移和氧化/还原。为了揭示开关过程中的主要现象，也就是说，扩散和氧化/还原过程，法拉第转移数被测量为理解整个开关过程的关键参数。

The operating mechanism of the resistive switches, namely the formation and annihilation of a metal filament, is understood to be based on the oxidation and reduction of metal atoms (ions) in the solid-electrolyte materials. However, a variety of phenomena in the switching operation, such as migration of metal ions in materials, oxidation and reduction processes at interfaces between a solid-electrolyte and a metal electrode, are not yet revealed on the atomistic level. These fundamental understandings are essential for clarifying the ultimate physical limits of down-scaling of actual nanodevices. In addition, the physics of the resistive switches should be established prior to introducing these radically new devices into nowadays semiconductor circuits. Because the operating mechanism is much different from that of semiconductor devices, adequate analytical methods and models for calculations are also required to be newly developed.In the project, ionic transfer and oxidation/reduction of metal ions are studied with respect to materials used as ionic conductors and electrodes, to device structures, to forming and operating conditions, and so on. To reveal the main phenomena in the switching, i.e., diffusion and oxidation/reduction processes, the Faradaic transfer number is measured as a key parameter to understand the whole switching process.