【公開日：2024.07.25】【最終更新日：2024.06.26】

課題データ / Project Data

課題番号 / Project Issue Number

23HK0055

利用課題名 / Title

Improve Charge Transfer under Strong Coupling Condition via Interfacial modification

利用した実施機関 / Support Institute

北海道大学 / Hokkaido Univ.

機関外・機関内の利用 / External or Internal Use

内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)

技術領域 / Technology Area

【横断技術領域 / Cross-Technology Area】（主 / Main）加工・デバイスプロセス/Nanofabrication（副 / Sub）計測・分析/Advanced Characterization

【重要技術領域 / Important Technology Area】（主 / Main）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions（副 / Sub）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion

キーワード / Keywords

蒸着・成膜/ Vapor deposition/film formation,ALD,スパッタリング/ Sputtering,光リソグラフィ/ Photolithgraphy,膜加工・エッチング/ Film processing/etching,電子顕微鏡/ Electronic microscope,走査プローブ顕微鏡/ Scanning probe microscope,光学顕微鏡/ Optical microscope,赤外・可視・紫外分光/ Infrared/visible/ultraviolet spectroscopy,原子薄膜/ Atomic thin film,スピン制御/ Spin control,表面・界面・粒界制御/ Surface/interface/grain boundary control,太陽電池/ Solar cell,電極材料/ Electrode material,太陽電池/ Solar cell,ALD,電子分光/ Electron spectroscopy,原子薄膜/ Atomic thin film

利用者と利用形態 / User and Support Type

利用者名（課題申請者）/ User Name (Project Applicant)

CAO En

所属名 / Affiliation

北海道大学　情報科学研究科

共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes

ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes

Xu Shi,Yasutaka Matsuo,Hiroaki Misawa

利用形態 / Support Type

（主 / Main）機器利用/Equipment Utilization（副 / Sub）,技術補助/Technical Assistance

利用した主な設備 / Equipment Used in This Project

HK-609：ヘリコンスパッタリング装置
HK-625：高分解能電界放射型走査型電子顕微鏡
HK-603：超高速スキャン電子線描画装置(130kV)
HK-404：超高分解能電界放出形走査電子顕微鏡
HK-617：原子層堆積装置（粉末対応型）

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

Plasmon-induced hot electron transfer has been attracting increased attention for the application of effective utilization of solar energy. Recently, the incorporation of gold (Au) nanostructures with wide-bandgap semiconductors such as titanium dioxide (TiO₂) has been demonstrated to enhance the photochemical activity in the visible region due to the localized surface plasmon resonances (LSPRs) of Au nanostructures. Under the surface plasmon excitation, energetic electrons can transfer from Au nanostructure into the conduction band (CB) of TiO₂ over the Schottky barrier. The interfacial structure of the Au nanostructure/TiO₂ heterojunction thus plays an important role in the electron transfer as well as the subsequent chemical reaction. Therefore, it is highly desired to modulate the interfacial structure between Au nanostructure/TiO₂ rationally to promote electron transfer. 

実験 / Experimental

ATA with different adhesion layer thicknesses was fabricated according to the following procedures. An Au-film and TiO₂ film are deposited on the SiO₂ substrate by sputtering and atomic layer deposition (ALD). Patterns of Au-NDs with a diameter of 80 nm were fabricated on TiO₂ film using EBL and lift-off techniques. During the Au-NDs fabrication,  the 0.5-10.0 nm thick Ti-film was first deposited onto the different substrates using electron-beam evaporation as the adhesion layer, followed by the deposition of a 30 nm-thick gold film. Field-emission scanning electron microscopy and a photonic multichannel analyzer were used to characterize the morphologies and far-field spectral properties of ATA structures. n time-resolved photoemission electron microscopy (TR-PEEM), a femtosecond laser excitation source was used to deliver 7-fs laser pulses, and the interferometric time-resolved apparatus consisted of a Mach-Zehnder interferometer. During the transient absorption measurement, the fundamental output from a regenerative amplified Ti: sapphire laser (800 nm femtosecond pulses with a repetition rate of 1000 Hz and a pulse duration of 25 fs) is split into two parts as pump and probe pulses.  Moreover, the study of near-field transfer between Au-NDs and Ti was performed using the finite-difference time-domain (FDTD) method.

結果と考察 / Results and Discussion

From the optical study, we found that the ATA structures with different thicknesses of Ti-layers exhibit strong coupling between the Fabry-Pérot nanocavity modes of the TiO₂/Au film and LSPR of Au NDs, and the strong coupling induced two absorption bands were observed with high light absorption. Due to the damping effect of the Ti-layer, the coupling strength of the modal strong coupling decreased as the thickness of the Ti-layer increased. With this ATTA structure, we verified the efficiency of electron injection into the CB of TiO₂ as a function of Ti layer thickness. As a result, we confirmed that the AQE of electron injection into TiO₂ increases by a factor of approximately 1.8 with increasing Ti layer thickness from 0.5 nm to 5.0 nm. To understand the mechanism of this phenomenon, we inserted a SiO₂ layer at the AuND/Ti layer interface and investigated the AQE dependence on the SiO₂ layer thickness. The results show that the energy transfer from AuNDs to the Ti layer was induced through the near-field in the ATTA structure, resulting in a production of high-energy electrons in the Ti layer to inject into the CB of TiO₂, thereby improving electron transfer efficiency.

図・表・数式 / Figures, Tables and Equations

 Time profiles of the TA measurements pumped at the upper branch (a) and lower branch (b). The inserted scale bars in (a) and (b) indicate ΔOD of 2 x 10^-3. (c) N-AQE as a function of Ti layer thickness. (d) ΔOD_max as a function of different pump wavelengths of Ti(5.0 nm)-ATTA. The absorption spectrum was also superposed.

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

References
[1]. Shi, X.; Li, X.; Toda, T.; Oshikiri, T.; Ueno, K.; Suzuki, K.; Murakoshi, K.; Misawa, H., Interfacial Structure-Modulated Plasmon-Induced Water Oxidation on Strontium Titanate. ACS Applied Energy Materials 2020, 3, 5675-5683.
[2] Shi, X.; Ueno, K.; Oshikiri, T.; Sun, Q.; Sasaki, K.; Misawa, H., Enhanced Water Splitting under Modal Strong Coupling Conditions. Nat Nanotechnol 2018, 13, 953-958.
[3] Liu, Y. E., et al., Quantum-Coherence-Enhanced Hot-Electron Injection under Modal Strong Coupling. ACS Nano 2023.
[4] Suganami, Y.; Oshikiri, T.; Shi, X.; Misawa, H., Water Oxidation under Modal Ultrastrong Coupling Conditions Using Gold/Silver Alloy Nanoparticles and Fabry-Perot Nanocavities. Angew Chem Int Ed Engl 2021, 60, 18438-18442. 
Acknowledgements
We acknowledge financial support from The Japan Society for the Promotion of Science (JSPS) KAKENHI, Grant Numbers JP23H05464, JP23H01916, JP23K04902， JP22K19003, JP22H05136, JP22H05131(a Grant-in-Aid for Transformative Research Areas "Evolution of Chiral Materials Science using Helical Light Fields"), JP21H04657, JP21H01736, JP18H05205. (A part of) This work was supported by “Advanced Research Infrastructure for Materials and Nanotechnology in Japan (ARIM)” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT). Proposal Number JPMXP1223HK0055. This work was also supported by “Crossover Alliance to Create the Future with People, Intelligence and Materials” from MEXT, Japan.
Oral Presentations
[1]En Cao, Xu Shi, Quan Sun,Shuai Zu, Tomoya Oshikiri, Hiroaki Misawa,"Effect of adhesion layer on hot electron transfer from metallic nanostructures to semiconductor under modal strong coupling condition"International Conference on Photochemistry (Switzerland_online), 2021.7.18-2021.7.23, Poster presentation
[2] En Cao, Xu Shi, Quan Sun,Shuai Zu, Tomoya Oshikiri, Hiroaki Misawa"Effect of adhesion layer on hot electron transfer from metallic nanostructures to semiconductor under modal strong coupling conditions"The Japanese Photochemistry Association (online),2021.9.13-2021.9.15, Poster presentation
[3] En Cao, Quan Sun, Shuai Zu, Xu Shi, Tomoya Oshikiri, Hiroaki Misawa“Effect of Metallic Adhesion Layer on Plasmon Induced Photocurrent Generation”The International Chemical Congress of Pacific Basin Societies (American_online), 2021.12.16-2021.12.21,, Poster presentation
[4]En Cao, Xu Shi, Yocefu Hattori, Quan Sun, Tomoya Oshikiri, Hiroaki Misawa“Improve Charge Transfer under Strong Coupling Conditions via Interfacial Modulation”The Japanese Photochemistry Association (Kyoto),2022.9.13-2022.9.15, Poster presentation

成果発表・成果利用 / Publication and Patents

論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)

1. En Cao, Improving Charge Transfer under Strong Coupling Conditions via Interfacial Modulation, ACS Photonics, 11, 1205-1212(2024).
   DOI: 10.1021/acsphotonics.3c01733
   

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

1. En Cao, Xu Shi, Yocefu Hattori, Quan Sun, Tomoya Oshikiri, Hiroaki Misawa,“Improve Charge Transfer under Strong Coupling Conditions via Interfacial Modulation” International Conference on Photochemistry (Japan), 2023.7.23-2023.7.28, Poster presentation

特許 / Patents

特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件