Open up Future Electronics by Organic Molecules

 

 Organic molecules are attracting recent attention as new ingredients of electronic circuits. Their functionalities have been developed considerably, but are still to be explored and advanced. Our group focuses on the development of organic electronics in the next era by providing new mechanism and concepts of the device operation and fabrication. For example, an electronic phase transition is utilized for the ON/OFF switching of our field-effect-transistor (FET). This special FET is called an organic Mott-FET, where the conduction electrons in the organic semiconductor are solidified at the OFF state because of Coulomb repulsion among carriers. In the operation, these solidified electrons can be melted by applying a gate voltage, and show an insulator-to-metal transition so-called Mott-transition to be switched to the ON state. Because of this phase transition, a large response of the device can be achieved, resulting in the highest device mobility ever observed for organic FETs. In addition to this high performance, the Mott-FET is interesting in terms of superconductivity. Because the Mott-transition often accompanies superconducting phase at low temperature,  modulation of gate electric field may induce superconductivity. This type of electric-field-induced superconducting transition can be utilized for mapping the phase diagram around the Mott-insulator. 

 -->  Strongly-correlated electron devices

 Another approach to the future electronics is the development of spintronic devices based on chirality of organic material. We aim to implement chirality-induced spin selectivity (CISS) effect into molecular devices that can generate spin-polarized current. This type of device is expected to realize spintronics devices without magnet or topological insulator.

  -->  Organic spintronics based on chirality

Because each molecule can be designed to show different functionalities, it should be attractive to assemble those molecules into nano-structured devices with integrated operation. We are especially focusing on a development of supramolecular nanowires that allow 3D periodic wiring in nano-scale. By encapsulating a 1D array of conducting molecules in a channel formed inside 3D supramolecular network, it is possible to construct a sheathed nanowires aligned in a periodic order.

  -->  Supramolecular nanowires

 

img_yamamoto01

Fig. 1 (left) Microscope image for FET device made of an organic Mott-insulator; Fig. 2 (center) Gate-voltage dependence of carrier concentration at an organic Mott-FET interface; Fig. 3 (right) Crystal structure for an organic supramolecular nano-wire.

References

  1. M. Suda, Y. Thathong, V. Promarak, H. Kojima, M. Nakamura, T. Shiraogawa, M. Ehara and H. M. Yamamoto, "Light-driven molecular switch for reconfigurable spin filters" 
    Nature Commun., 2455 (2019).
  2. M. Suda, R. Kato, and H. M. Yamamoto, "Light-induced superconductivity using a photo-active electric double layer"
    Science, 347, 743-746 (2015).
  3. H. M. Yamamoto, M. Nakano, M. Suda, Y. Iwasa, M. Kawasaki and R. Kato, "A strained organic field-effect transistor with a gate-tunable superconducting channel"
    Nature Commun., 4, 2379/1–2379/7 (2013).
  4. Y. Kawasugi, H. M. Yamamoto, N. Tajima, T. Fukunaga, K. Tsukagoshi, and R. Kato, "Electric-Field-Induced Mott Transition in an Organic Molecular Crystal"
    Phys. Rev. B, 84, 125129/1-125129/9 (2011).
  5. H. M. Yamamoto, Y. Kosaka, R. Maeda, J. Yamaura, A. Nakao, T. Nakamura, and R. Kato, “Supramolecular Insulating Networks Sheathing Conducting Nanowires Based on Organic Radical Cations” ACS Nano, 2(1), 143-155 (2008).

Keywords: Organic Electronics, Organic FET, Strongly-correlated electron systems, superconductivity, Mott-insulator, Mott-transition, Supramolecular nanowire, Organic spintronics, Chirality-induced spin selectivity