Exploration of physical properties of monochalcogenide in ultra-thin film form

• Project/Area Number: 18H01865
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Tohoku University
• Principal Investigator: Shiogai Junichi 東北大学, 金属材料研究所, 助教 (30734066)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥18,070,000 (Direct Cost: ¥13,900,000、Indirect Cost: ¥4,170,000); Fiscal Year 2020: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000); Fiscal Year 2019: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000); Fiscal Year 2018: ¥14,690,000 (Direct Cost: ¥11,300,000、Indirect Cost: ¥3,390,000)
• Keywords: モノカルコゲナイド / 超伝導 / 半導体 / 薄膜 / 2次元物質 / 薄膜成長 / ヘテロ構造 / エッチング

Outline of Final Research Achievements

To study the impact of the reducing the thickness on the physical properties of monochalcogenides, we applied thin-film growth technique to iron-based superconductor FeSe and semiconductor InSe. While a bulk FeSe exhibits a superconducting transition temperature (Tc) at 8 K, Tc is greatly improved to 40 K for a monolayer FeSe. We established tunneling spectroscopy device based on FeSe by using InSe as a tunneling barrier, which allows a direct comparison between resistive Tc and superconducting gap. For InSe thin films, we found that a optical bandgap of InSe is increased from 1.2 eV for bulk to 3.2 eV for monolayer.

Academic Significance and Societal Importance of the Research Achievements

本研究のFeSe薄膜のトンネル分光測定技術により、抵抗測定による超伝導転移温度と超伝導ギャップを直接比較することが可能となった。これまで報告されている単層FeSeの超伝導転移温度は40Kである。一方、分光学的手法によるギャップ測定では65Kの転移温度に相当する超伝導ギャップが測定されている。しかし、これらは同一試料・条件で行われていないため、超伝導発現機構が未解明である。本手法を用いることで、単層高温超伝導相の物理的描像の理解が進むと期待される。また、InSeにおいては、1.2eVから3.2eVまで広い範囲でバンドギャップを制御することができるため、広帯域の光電子素子としての利用が期待される。

Research Products

• [Journal Article] Two-dimensional growth of conductive ultra-thin Sn films on insulating substrate with an Fe buffer layer (2020)
  • Author(s): Zheng Dingheng、Shiogai Junichi、Inoue Hisashi、Souma Seigo、Sato Takafumi、Tsukazaki Atsushi
  • Journal Title: APL Materials Volume: 8 Issue: 6 Pages: 061103-061103
  • DOI: 10.1063/5.0009012
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Pulsed-laser deposition of InSe thin films for the detection of thickness-dependent bandgap modification (2018)
  • Author(s): Zheng Dingheng、Shiogai Junichi、Fujiwara Kohei、Tsukazaki Atsushi
  • Journal Title: Applied Physics Letters Volume: 113 Issue: 25 Pages: 253501-253501
  • DOI: 10.1063/1.5064736
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Thickness-Dependent Optical Bandgap and Electrical Transport Properties in InSe Thin Films Grown by Pulsed-Laser Deposition (2019)
  • Author(s): D. Zheng, J. Shiogai, K. Fujiwara, A. Tsukazaki
  • Organizer: 2019 MRS Fall Meeting
  • Int'l Joint Research
• [Presentation] Thickness-dependent Optical Bandgap and Electrical Transport Properties in Layered InSe Thin Films Grown by Pulsed-laser Deposition (2019)
  • Author(s): D. Zheng, J. Shiogai, K. Fujiwara, and A. Tsukazaki
  • Organizer: MRM 2019
  • Int'l Joint Research
• [Presentation] Pulsed-laser deposition of layered InSe thin films for investigation of thickness-dependent bandgap modification (2018)
  • Author(s): D. Zheng, J. Shiogai, K. Fujiwara, and A. Tsukazaki
  • Organizer: Summit of Materials Science 2018 in Sendai, Japan
  • Int'l Joint Research
• [Book] ポストグラフェン材料の創製と用途開発最前線、「FeSe電気二重層トランジスタの開発」 (2020)
  • Author(s): 塩貝 純一, 野島 勉, 塚﨑 敦
  • Total Pages: 11
  • Publisher: 株式会社エヌ・ティー・エス
• [Remarks]
  • URL: https://researchmap.jp/junichi.shiogai
• [Remarks]
  • URL: http://mu.imr.tohoku.ac.jp/memberlist_shiogai.html
• [Remarks]
  • URL: http://mu.imr.tohoku.ac.jp/memberlist_shiogai.html
• [Remarks]
  • URL: http://mu.imr.tohoku.ac.jp/memberlist_shiogai.html