Takafumi Ishibe

Thermoelectric thin films: fundamental methods for performance enhancement and recent progress

Yoshiaki Nakamura, Takafumi Ishibe

Abstract Thermoelectric (TE) thin film performances have been enhanced by the emergence of various methodologies of carrier and phonon transport controls. This review provides an overview of TE thin film advancement based on film technology with high controllability of crystal and material …

Boosting Seebeck coefficient through electron-phonon interaction by phonon frequency control

Asumi Michibata, T. TERADA, Kotaro Matsuzono, Takafumi Ishibe et autres

In Dirac and Weyl semimetals with a flat band, the Seebeck coefficient ($S$) can be enhanced by the energy filtering effect in wave number space through electron-phonon interaction (EPI). Especially, topological B20-type semimetal thin films are promising materials because their Dirac or …

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Effect of composition and strain on thermoelectric properties of p-type epitaxial GeSn film/Si

Arata Shibagaki, Ryosuke Hotta, T. TERADA, Takafumi Ishibe et autres

Abstract Ge 1− x Sn x is one of the promising group IV element-based thermoelectric materials. This study reveals the effect of the x and the strain on the thermoelectric properties of p-type epitaxial Ge 1− x Sn x films/Ge buffer layers/Si. …

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Non-parabolic Band Effect of ZnO Enhanced by Hybridization with Complex Point Defect Donors for Boosting Thermoelectric Conversion

Yuki Komatsubara, Takafumi Ishibe, Seiya Kozuki, Kazunori Satō et autres

at 300 K, which is the highest among all the transparent thermoelectric thin film materials ever reported. This method provides a new approach to increase the thermoelectric power factor.

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Robust thermoelectric power factor enhanced by energy filtering effect in B20-type CoSi films

Takafumi Ishibe, Takahiro Hinakawa, Shunya Sakane, Shintaro Ishigaki et autres

This study demonstrates that thermoelectric power factor (PF) of B20-CoSi with a peculiar electronic band structure (Dirac-like band and heavy hole band) surprisingly gets high regardless of crystal quality. We reveal that the high PF is attributed to energy filtering effect in …

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Controlling thermoelectric properties of epitaxial GeSn film/Si by tuning strain and composition

Arata Shibagaki, Ryosuke Hotta, Takafumi Ishibe, Yuichiro Yamashita et autres

We develop compressively-strained epitaxial Ge1−xSnx films with large x (>0.1) on Si substrates. Therein, large x and compressive biaxial strain cause a band convergence by movement of Γ valley down to L valleys near the Fermi level, which leads to high Seebeck …

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Selective Anion Manipulation for Controlling the Thermoelectric Properties of Epitaxial SnO2 Films on r-Al2O3

Takafumi Ishibe, Seiya Kozuki, Yuki Komatsubara, Yuto Uematsu et autres

Introducing defects is one of the promising approaches for enhancing the thermoelectric property. In this study, we substantially reduce thermal conductivity while maintaining a high thermoelectric power factor (PF) by selectively manipulating O 2– anion in domain-engineered SnO 2 with conduction and …

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Ultrahigh moisture electric output of oxidation-controlled and ion-intercalated graphene oxide films in the low humidity range

Takafumi Ishibe, Atsuhiro Yamamoto, Wataru Sasaki, Eiichi Kobayashi et autres

Crystallinity enhancement and ion intercalation enable ultrahigh moisture-induced electric output in graphene oxide films even at low humidity.

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Report on the Tenth U.S.-Japan Joint Seminar on Nanoscale Transport Phenomena

Renkun Chen, Chuanhua Duan, Takuma Hori, Wei‐Lun Hsu et autres

The tenth U.S.–Japan Joint Seminar on Nanoscale Transport Phenomena was held in San Diego, California, from July 16–19, 2023. The goals of the joint seminar series, established in 1993, are to encourage research and international exchange between US and Japan researchers in …

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Film Thermoelectric Generator of Multiple 2-D Electron Gas

Yuto Uematsu, Takafumi Ishibe, Seiya Kozuki, Takaaki Mano et autres

2-D electron gas (2DEG) is one of the promising approaches for high thermoelectric (TE) performance. However, high electrical resistance of the film originating from thin 2DEG conduction channel width and thick insulator layer is a bottleneck for obtaining high output power. In …

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Epitaxial growth of Ca(Ge₁₋ₓSnₓ)₂ with group IV 2D layers on Si substrate

Takashi Yoshizaki, T. TERADA, Yuto Uematsu, Takafumi Ishibe et autres

Yoshizaki T., Terada T., Uematsu Y., et al. Epitaxial growth of Ca(Ge₁₋ₓSnₓ)₂ with group IV 2D layers on Si substrate. Applied Physics Express 17, 055501 (2024); https://doi.org/10.35848/1882-0786/ad3ee2.

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Epitaxial growth of Ca(Ge1−xSnx)2 with group IV 2D layers on Si substrate

Takashi Yoshizaki, T. TERADA, Yuto Uematsu, Takafumi Ishibe et autres

Abstract Two-dimensional (2D) material is drawing considerable attention as a promising thermoelectric material. This study establishes the formation method of renewed Ca-intercalated group IV 2D materials, Ca(Ge1−x Sn x )2 crystals including germanene-based 2D layers. The solid phase epitaxy allows us to …

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