Emergent Iontronics

In your mobile phones, there are two kinds of important devices, billions of transistors and a battery. The transistor controls electron flow in a semiconductor to enable processing and storage of information, while the latter stores electrochemical energy for driving the former. In the latest decade, devices with combined concepts of transistors and batteries, electrochemical transistors, are receiving increasing interests, because they can offer new opportunities beyond conventional current switching functions of all solid transistors.Surprises came from a simple replacement of solid gate dielectrics in field effect transistors (FETs) with electrolytes, which low us to form two dimensional (2D) electron systems at the transistor channel with the density of 1014 cm-2, which is 1 – 2 orders of magnitude larger than that achieved in conventional FETs. This type of electrochemical transistor was named as electric double layer transistor (EDLT). Taking the advantage of ultrahigh density 2D electron systems, we have successfully realized electric field induced superconductivity [1], ferromagnetism [2], Mott-Hubbard transition [3], which have been impossible or at least extremely difficult in conventional all solid FETs. In particular, the 2D crystals from transition metal dichaocogenides and other layered materials offers an ideal platform for the EDLT device, due to their dangling bond free surface structures. In fact, we have demonstrated electric field induced superconductivity [4] and chiral light source [5] based on EDLTs of 2D crystals. Also, we found that the electric field induced superconductivity in the EDLT configurations provides novel plat forms of highly crystalline 2D superconductors [6, 7]. As such, EDLT is creating an innovative concept of field effect phase control in a variety of materials. In this lecture, I will review the current status of “Emergent Iontronics”, ion-controlled electronics [8].