Research Bits: September 5

Layered TMD semiconductors; neuromorphic electric double layer transistor.


Layered TMD semiconductors

Scientists from Tsinghua University investigated fabrication techniques for fabricating and engineering transition metal dichalcogenides (TMDs).

By modulating TMDs with various methods, including phase engineering, defect engineering, doping, and alloying, the material class could provide a wide range of alternatives for high-quality layered semiconductors with stable phase and suitable band structure. Additionally, the researchers said that non-semiconductor phases of layered semiconductors can be utilized as contacts, dielectrics, and interlayers to build high performance devices.

“In principle, this opens up the design of a whole new class of materials in photoelectronic applications, that have exhibited novel properties, such as superconductivity, spin-orbit coupling, ferroelectricity, and ferromagnetism,” said Chen Wang, an associate professor at the School of Materials at the Tsinghua University.

One of the material’s attractive characteristics is new options for the formation of heterostructures. For example, the synthesis of WS2-WSe2 and MoS2-MoSe2 lateral heterostructures can be synthesized through step-growth. Vertical heterostructure TMDs can be fabricated using either step growth or mechanical stacking.

The team is also exploring the heterogenous integration of layered semiconductors and traditional semiconductors. “[Van der Waals heterostructures] can be formed by combining different types of layered materials and traditional semiconductors to realize functional devices,” said Simian Zhang of Tsinghua University.

“We think that the heterogeneous integration between layered and traditional semiconductors, combining the technical and economic advantages of both materials system provides a practical middle route for the early stage of post Moore era,” added Wang.

Zhuofan Chen et al, Comparative coherence between layered and traditional semiconductors: unique opportunities for heterogeneous integration, 2023 Int. J. Extrem. Manuf. 5 042001

Neuromorphic electric double layer transistor

Researchers from Japan’s National Institute for Materials Science (NIMS) and the Tokyo University of Science created what it claims is the fastest neuromorphic electric double layer transistor using a highly ion conductive ceramic thin film and a diamond thin film.

An electric double layer transistor works as a switch using electrical resistance changes caused by the charge and discharge of an electric double layer formed at the interface between the electrolyte and semiconductor. They are slow in switching, however, with typical transition time ranges from several hundreds of microseconds to 10 milliseconds.

In the new device, an electric double layer if formed at the ceramic/diamond interface. The ceramic zirconia thin film is able to adsorb large amounts of water into its nanopores and allow hydrogen ions from the water to readily migrate through it, enabling the electric double layer to be rapidly charged and discharged. The team found that it operates 8.5 times faster than existing electric double layer transistors.

The team also confirmed the ability of the transistor to convert input waveforms into many different output waveforms with precision, giving it the potential for use in in edge AI devices for image, voice, and odor recognition.

Makoto Takayanagi, Daiki Nishioka, Takashi Tsuchiya, Masataka Imura, Yasuo Koide, Tohru Higuchi, Kazuya Terabe, Ultrafast-switching of an all-solid-state electric double layer transistor with a porous yttria-stabilized zirconia proton conductor and the application to neuromorphic computing, Materials Today Advances, Volume 18, 2023, 100393, ISSN 2590-0498,

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