Takayoshi Katase
Tokyo Institute of Technology, Japan
Title: Room-temperature-protonation-driven optoelectronic device with water-gated thin-film-transistor structure
Biography
Biography: Takayoshi Katase
Abstract
Using the flexible valence state of transition-metal ions in transition metal oxides (TMOs), the optoelectronic properties can be largely controlled through the electronic phase transitions. Protonation of TMOs is one of the modulation techniques because the proton in TMOs acts as shallow donors to donate an electron into TM cations, resulting in a dramatic change in the optoelectronic properties. However, the protonation needs high-temperature heating process or electrochemistry in liquid electrolyte and thus it has not been suitable for the device application. In this talk, we propose a new approach of RT-protonation of TMOs by using a solid-state thin-film-transistor-type structure with “liquid- leakage-free water”, in which water is infiltrated in a nanoporous glass, as the gate insulator and demonstrate the RT-protonation-driven infrared (IR) transmittance tunable metal-insulator conversion device by using a thermochromic vanadium dioxide (VO2) as the active channel layer. Alternative positive and negative gate-voltage applications induce the reversible protonation/deprotonation of VO2 channel and the double-digit sheet-resistance modulation and 49% modulation of IR-transmittance were simultaneously demonstrated at RT by the metal-insulator phase conversion of VO2 in a non-volatile manner. The present device is operable by the RT-protonation in all-solid-state structure and thus it will provide a new gateway for the development of functional optoelectronic devices.