Presenter: Dr. Takayoshi Katase (Hokkaido University)
Topic: Optoelectronic and electromagnetic switching device with transition metal oxides using water-leakage-free electrolyte
Time: 10:00 AM, Oct. 10th (Monday)
Location: Conference Room B, BLDG 909-1F
Opto-electronic and electro-magnetic properties of transition metal oxides (TMOs) can be modulated by modifying oxygen concentration and/or protonation due to the valence-state change of TM ions. For the application to multifunctional memory device, the functionality should be switched at room temperature (RT) by a solid-state device, but the switching classically needs high-temperature heating or electrochemical reaction with liquid electrolyte, which is not suitable for practical applications. We have proposed a new thin-film-transistor (TFT) structure with water-infiltrated nanoporous glass, amorphous 12CaO-7Al2O3, (CAN), as a gate insulator  and have demonstrated electric-field-induced 2 dimensional electron gas (2DEG) in SrTiO3 single crystal; the 2DEG layer with electron carrier density up to ~1015 cm?2 exhibits an unusually large thermopower . For VO2-based TFTs, we have realized the RT-protonation-driven metal-insulator phase modulation, leading to the on-demand control of infrared transmittance for advanced smart windows . For WO3-based TFTs, we have demonstrated an electrochromic metal-insulator switching device, which exhibits multi-functionality of electrochromism and electrical-switching by RT-protonation . For SrCoOx-based TFTs, an antiferromagnetic insulator (AFM-SrCoO2.5)was reversibly controlled to a ferromagneticmetal (FM-SrCoO3) by electrochemical redox reaction at RT . The present device can switch the functional properties of TMOs at RT by using ‘water-leakage-free electrolyte’, which will provide a novel design concept for TMO-based practical memory devices.
 H. Ohta et al., Nature Commun.1, 118 (2010),  H. Ohta et al., Adv. Mater.24, 740 (2012),  T. Katase et al., Adv. Electron. Mater.1, 1500063 (2015),  T. Katase et al., Adv. Electron. Mater. 2, 1600044 (2016),  T. Katase et al., Sci. Rep.6, 25819 (2016).
Dr. Katase is currently Assistant Professor in the group of Prof. Hiromichi Ohta at Research Institute for Electronic Science at Hokkaido University, Japan. He obtained a B.S. from Tokyo Institute of Technology, Japan in 2007 and a M.S. from Tokyo Institute of Technology, Japan in 2009, and a Ph.D. from Tokyo Institute of Technology, Japan in 2012.
Contact: Prof. Steffen Duhm