Ionic Nanoarchitectonics: Creation of Polymer-Based Atomic Switch and Decision-Making Device

In order to realize a super-smart society for the next generation, not only conventional semiconductor devices but also novel devices that operate on completely different principles have been attracting much attention. As one group of these new concept devices, solid-state nanoionic devices that operate using local ion movement in solids are expected. In this devices, interesting physical properties are generated by nanoscale structural modulations due to local ion movement near the interfaces between electrodes and ionic conductors (referred to as ionic nanoarchitectonics). So far, we have been controlling the point contact, the Schottky-like barrier, the solid electric double layer, the electrochemical reaction, etc. by interface modulations utilizing the ionic nanoarchitectonics. Through these controls, we have created nanoionic devices that enable various new functions such as atomic switches, artificial synapses, decision-making devices, superconducting-transition-temperature variable devices, magnetic variable devices, and band gap variable devices. In this chapter, as representative examples of nanoionic devices created using the ionic nanoarchitectonics, the atomic switch using solid polymer electrolytes and the decision-making device using ion transfer were described in detail. With the further progress of these nanoionic devices, it is expected to develop a new artificial intelligence (AI) system that performs analog information processing by using the physical properties of hardware, which is different from the conventional AI system that performs digital information processing by using software and big data.