International Center for Materials Nanoarchitectonics eBulletin: Next Generation Innovative Organic Electronics

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September 2018 issue of MANA eBulletin

http://www.nims.go.jp/mana/ebulletin/     

Feature 
Next Generation Innovative Organic Electronics 
Yutaka Wakayama, Deputy Director, MANA 
MANA researchers are integrating flexible organic devices for functional logic circuits to processing data. 
http://www.nims.go.jp/mana/ebulletin/feature.html

Serendipitous discovery of conducting polymers in the mid-1970s, the implications of which were recognized with a Noble Prize in Chemistry for Heeger, MacDiarmid and Shirakawa in 2000. This and related research on organic materials for applications in electronic devices led to the birth and proliferation of touch screens of smart phones, organic photovoltaic devices, and the dawn of flexible organic electronic devices that can be worn, like a suit and tie.

"The potential of flexible organic materials for fabricating sensors, displays and sources of tunable light, for example, is the driving force pushing research in this area of materials science," says Yutaka Wakayama, an expert in organic electronics and Deputy Director, MANA. "The challenge facing the organic electronics community is to integrate flexible devices to enable functional, and useful data processing for practical applications such as logic operations and switching. Solving these issues has been the driving force for my research over the last decade or so."

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Caption: Nanoarchitectonic of molecular functions for nanoelectronics

Research Highlights 
Evidence of A New Type of Quantum Effect  
http://www.nims.go.jp/mana/research/highlights/vol41.html 
Moriyama and colleagues demonstrated the quantum valley Hall effect in a special heterostructure capable of hosting a two-dimensional electron gas: a sheet of graphene sandwiched between hexagonal boron nitride (h-BN) layers. Graphene is a one-atom thin layer of carbon atoms forming a honeycomb pattern. h-BN is similar; it is also a monolayer with a honeycomb structure, but it has a slightly different lattice parameter. Due to the mismatch in lattice size, the periodicity of the combined system is much larger - overlaying the two lattices results in a moiré pattern.

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Figure: (A) Device structure. (B) Hofstadter's butterfly, a quantum Hall effect in graphene/h-BN superlattice heterostructure. (C) and (D) Signature of the quantum valley Hall effect in a graphene/h-BN superlattice.

Reference 
K. Komatsu et al., "Observation of the quantum valley Hall state in ballistic graphene superlattices", Sci. Adv. 4:eaaq0194 (2018).

Flexible Organic Electronic Devices for Three-Valued Logic Circuitry 
http://www.nims.go.jp/mana/research/highlights/vol42.html

Wearable and flexible integrated-circuit technology is on the rise, especially in the context of the 'internet of things (IoT)' - devices sharing information through the internet. So-called organic field-effect transistors (OFETs), built from organic molecules, are mechanically flexible, and therefore suitable for IoT electronics. OFETs are difficult to downsize, however, making their high-density integration onto flexible chips problematic. Yutaka Wakayama at the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan, and colleagues have now presented an alternative approach. Rather than considering OFETs offering conventional two-valued logic - with zeroes and ones - they developed a circuit element, built from organic materials, capable of handling three logical values.

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Figure: A ternary inverter based on organic electronic materials.

Reference   
K. Kobashi et al., "Multi-Valued Logic Circuits Based on Organic Anti-ambipolar Transistors", Nano Lett.18, 4355-4359 (2018).

New approach for the synthesis of carbon nanosheets 
http://www.nims.go.jp/mana/research/highlights/vol43.html 
Carbon nanosheets - thin materials consisting of only carbon - have many useful properties, including energy-storage and catalytic functionality. The large-scale production of carbon nanosheets, however, has been challenging.

Now, Taizo Mori and Katsuhiko Ariga at the World Premier International Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan, and colleagues have discovered a relatively simple method for the fabrication of large carbon nanosheets.

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Figure: Synthesis of carbon nanosheets from CPPhen molecules.

Reference   
Taizo Mori et al., "Carbon Nanosheets by Morphology-Retained Carbonization of Two-Dimensional Assembled Anisotropic Carbon Nanoring", Angew. Chem. Int. Ed. 57, 9679-9683 (2018).

Further information
The International Center for Materials Nanoarchitectonics (WPI-MANA), Japan
1-1 Namiki Tsukuba-shi Ibaraki, 305-0044 JAPAN
Tel: (+81) 029-860-4710
Email: mana-pr@ml.nims.go.jp
http://www.nims.go.jp/mana/