【公開日：2024.07.25】【最終更新日：2024.06.24】

課題データ / Project Data

課題番号 / Project Issue Number

23HK0081

利用課題名 / Title

Nanostructure fabrication for plasmonic and photonic applications

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）次世代ナノスケールマテリアル/Next-generation nanoscale materials（副 / Sub）高度なデバイス機能の発現を可能とするマテリアル/Materials allowing high-level device functions to be performed

キーワード / Keywords

ALD,スパッタリング/ Sputtering,電子線リソグラフィ/ EB lithography,電子顕微鏡/ Electronic microscope,電子回折/ Electron diffraction,電子分光/ Electron spectroscopy,原子層薄膜/ Atomic layer thin film,ナノ粒子/ Nanoparticles,フォトニクスデバイス/ Nanophotonics device

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)

笹木 敬司

所属名 / Affiliation

北海道大学 電子科学研究所・光システム物理分野

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

杉山 輝樹,藤原 英樹,PIN Christophe,CHENG An-Chieh

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

松尾保孝,石旭,佐々木仁,ピョーテンダーテン,遠堂敬史,大西広,細井浩貴,中村圭佑,浮田桂子,小島俊哉,福本愛

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-602：超高精度電子ビーム描画装置(125kV)
HK-609：ヘリコンスパッタリング装置
HK-611：多元スパッタ装置
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)

This work aims at studying the synthesis or crystallization of nanomaterials using gold plasmonic nanostructures. By exciting the plasmonic resonance of gold nanostructures, both optical forces and photothermal effect can be locally enhanced and controlled by tuning the incident light properties (wavelength, polarization, orbital angular momentum, etc). It was demonstrated that the optical forces in the vicinity of the central nanogap of a plasmonic trimer nanostructure can efficiently induce the chiral crystallization of EDS crystals. Morevover, the chirality of the EDS crystal can be controlled via the transfer of angular momentum from the incident light to the evanescent field localized near the nanogap. It was also demonstrated that heating due to plasmon resonance excitation can locally trigger the hydrothermal synthesis reaction of VO2. This new VO2 synthesis technique may be used to fabricate tunable, hybrid nanophotonic devices.

実験 / Experimental

30 nm-thick gold plasmonic nanostructures (with a 3 nm chromium adhesion layer) with specific plasmonic properties were fabricated by e-beam lithography, sputtering, and lift-off method. Especially, multimer nanostructures composed of several gold particles forming nanogaps of less than 30 nm have been fabricated. Deposition of an alumina thin film (3 nm) was performed by ALD to promote the adhesion of VO2 on the plasmonic nanostructures. After fabrication, the nanostructures were imaged by SEM technique and the synthesized vanadium oxide nanomaterials were characterized by EDS technique.

結果と考察 / Results and Discussion

Large arrays of plasmonic gold trimer nanostructures were designed based on numerical simulation results and fabricated on a glass substrate. A 1064 nm laser light was tightly focused to excite the plasmonic resonance of a single nanostructure located near the liquid solution-air interface. Rapid crystallization of EDS was achieved due to the large electric field enhancement in the vicinity of the central nanogap. By tuning the spin and orbital angular momentum states of the incident light, enantioselective crystallization of ethylenediamine sulfate (EDS) was demonstrated. Crystal enantiomeric excess (CEE) values reaching 44% were achieved with p values below 0.005 ensuring that the experimental results are statistically significant. The dominant chiral form of the crystals formed during the experiments was found to vary according to the value of the total angular momentum carried by the incident photons. As shown in Figure 1(a), increasing the total angular momentum from 1ℏ (circularly polarized Gauss beam) to 2ℏ (circularly polarized Laguerre-Gauss beam) leads to the reversal of the rotation direction of the Poynting vector nanovortex formed above the plasmonic trimer nanogap. This Poynting vector nanovortex creates a torque that is, together with the attractive gradient force, responsible for the helical force field above the nanogap. Good agreement was found between the numerical results and the dominant type of chiral crystal formed under the different laser excitation conditions.

30nm-thick gold nanodisks and nanobar structures were also fabricated on glass substrate to demonstrate the plasmon-assisted hydrothermal synthesis VO₂ on plasmonic nanostructures. Prior to the experiments, the gold nanostrucutres were coated with a 3 nm-thick layer of alumina to promote the adhesion of the synthesized VO₂ nanomaterials. After immersion in a precursor solution, a 1064 nm laser beam was focused on a nanostructure that acts as a much-localized heat source. The temperature rise was large enough to locally trigger the synthesis of vanadium oxide nanomaterials. As shown in Figure 1(b) and (c), the material synthesis can be spatially controlled by exciting the localized surface plasmon resonance of a specific gold nanobar structure. The site-selective VO₂ synthesis was also achieved by tuning the length of coupled nanobars irradiated using circularly polarized light. The plasmon-assisted hydrothermal synthesis of VO₂ may enable the fabrication of tunable, hybrid micro- and nanodevices for photonic and optoelectronic applications.

図・表・数式 / Figures, Tables and Equations

Fig.1 (a) SEM image of a gold trimer nanostructure. Numerical simulation results show that the rotation direction of the Poynting vector nanovortex above the central nanogap depends on the excitation condition (top: right-handed circularly polarized Gauss beam; bottom: right-handed circularly polarized right-handed Laguerre-Gauss beam). Consequently, EDS crystal with opposite chirality are favored. (b,c) SEM images of two perpendicular gold nanobar structures (b) before and (c) after the hydrothermal synthesis of VO₂ around the horizontal nanobar. The site-selective material synthesis is achieved by selectively exciting the plasmon resonance of the horizontal nanobar using an incident laser beam with a horizontal linear polarization.

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

This work was supported by JSPS KAKENHI (Grants JP16H06506, JP18H03882, JP18H05205, and JP21H04657 to KS and JP20K15145, JP22H01923 to CP), grants from the National Science and Technology Council (NSTC) in Taiwan (grant Nos. MOST 110–2113-M-A49–012-MY3 and MOST 111-2634-F-A49-007 to TS), JSPS KAKENHI Grant-in-Aid (No. JP22H05138 to TS and JP23H04571 to CP) for Transformative Research Areas (A) "Revolution of Chiral Materials Science using Helical Light Fields" from the Japan Society for the Promotion of Science (JSPS), the AMADA Foundation (AF-2021238-C2, AF-2021226-B3). The authors are also grateful for the support of the Center for Emergent Functional Matter Science of National Yang Ming Chiao Tung University from the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan and the Research Program of "Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials" in "Network Joint Research Center for Materials and Devices". 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). Grant Number JPMXP1223HK0081(Hokkaido University).

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. Yuji Sunaba, Nano-shaping of chiral photons, Nanophotonics, 12, 2499-2506(2023).
   DOI: 10.1515/nanoph-2022-0779
   
2. An-Chieh Cheng, Enantioselectivity in Chiral Crystallization Driven by the Canonical and Spin Momentum Forces of Optical Vortex Beams, The Journal of Physical Chemistry C, 128, 4314-4320(2024).
   DOI: 10.1021/acs.jpcc.3c08424
   
3. An-Chieh Cheng, Spiral-structured crystal of ethylenediamine sulfate fabricated by optical trapping, Optical Manipulation and Structured Materials Conference, , 39(2023).
   DOI: 10.1117/12.3008363
   

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

1. CHENG An-Chieh, PIN Christophe, 砂場侑司, 杉山輝樹, 笹木敬司, "Nanoscale Helical Optical Force for Determining Crystal Chirality" Small, accepted
2. CHENG An-Chieh, 杉山輝樹, 笹木敬司, "Spiral-structured crystal of ethylenediamine sulfate fabricated by optical trapping" SPIE Optical Manipulation and Structured Materials Conference (横浜), 令和５年４月１７～２１日
3. CHENG An-Chieh, 杉山輝樹, 笹木敬司, "Plasmonic trapping-induced enantioselective crystallization of organic compounds with metal nanostructures" ICP2023 (札幌), 令和５年７月２４日
4. PIN Christophe, 藤原英樹, 笹木敬司, "Laser-induced hydrothermal synthesis of vanadium dioxide on gold thin films and nanostructures" ICP2023 (札幌), 令和５年７月２４日
5. PIN Christophe, 藤原英樹, 笹木敬司, "Fabrication of vanadium dioxide micro- and nanostructures by laser-induced hydrothermal synthesis" META2024 (富山), 令和６年７月１６～１９日

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