研究者詳細 - 山本　瑛祐

Pseudo-topotactic Transformation from Oxide Nanosheets to Amorphous Nanosheets 査読有り

Sugimoto, H; Kobayashi, M; Yamamoto, E; Osada, M

CHEMISTRY LETTERS 52 巻 ( 5 ) 頁： 322 - 324 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemistry Letters

We demonstrated the synthesis of amorphous oxide nanosheets from crystalline nanosheets prepared by the exfoliation of layered compounds. Single-crystalline oxide nanosheets were calcined with C3N4 powder in flowing nitrogen and annealed in air to produce amorphous oxide nanosheets. The cation composition and valence, shape, lateral size, surface roughness, and thickness were not changed by treatment. This approach enables the production of amorphous oxide nanosheets with distinct morphologies and compositions and large lateral sizes.

DOI： 10.1246/cl.230073

CiNii Research

Composite design of two-dimensional inorganic nanosheets for flexible energy storage capacitors 査読有り

Byun, KN; Shi, Y; Yamamoto, E; Kobayashi, M; Osada, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 131 巻 ( 4 ) 頁： 77 - 82 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

We present a new approach for designing flexible energy storage capacitors using two-dimensional (2D) inorganic nanosheets. 2D dielectric Ca2Nb3O10 nanosheet and ferroelectric poly(vinylidene fluoride) (PVDF) were selected as model material systems. LangmuirBlodgett deposition was utilized for layer-by-layer engineering of (Ca2Nb3O10/PVDF) nanocomposite films on an indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. Such a new composite design realized the simultaneous improvement of energy density (37 J cm13) and efficiency (378 %) even in the ultrathin form (320 nm) on the ITO-coated PET substrate. Nanosheet-based flexible capacitors also maintained a stable performance even after 104 times bending cycles. These results indicate that our nanosheet approach is of technological importance for exploring new flexible dielectric capacitors.

DOI： 10.2109/jcersj2.22150

CiNii Research

Molecularly Thin BaTiO<sub>3</sub> Nanosheets with Stable Ferroelectric Response 査読有り

Hagiwara, K; Byun, KN; Morita, S; Yamamoto, E; Kobayashi, M; Liu, XY; Osada, M

ADVANCED ELECTRONIC MATERIALS 9 巻 ( 4 ) 頁： 2201239 - 2201239 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Electronic Materials

2D ferroelectrics provide great promise for future electronics owing to their unique properties at 2D limit. Although simple perovskite oxides (such as BaTiO3 and PbTiO3) are an important target for 2D ferroelectrics, controlled synthesis of 2D nanosheets still remains a challenge. Here, this issue is addressed by using a new chemical protocol; unilamellar Ti0.87O2 nanosheets can serve as templates, guiding the solvothermal synthesis of 2D BaTiO3 nanosheets with a molecularly thin thickness (< 3 nm). Raman spectroscopy, second-harmonic generation, and transmission electron microscopy characterizations suggest the formation of tetragonal ferroelectric BaTiO3 nanosheets. Based on piezoresponse force microscopy, BaTiO3 nanosheets exhibit a clear ferroelectric response with a high Curie temperature (≈100 °C) even down to 1.8 nm thickness. This study provides new opportunities to investigate perovskite ferroelectrics with the critical thickness.

DOI： 10.1002/aelm.202201239

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/aelm.202201239

Automated One-Drop Assembly for Facile 2D Film Deposition 査読有り

Shi, Y; Yamamoto, E; Kobayashi, M; Osada, M

ACS APPLIED MATERIALS & INTERFACES 15 巻 ( 18 ) 頁： 22737 - 22743 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Materials and Interfaces

The effective application of 2D materials is strongly dependent on the mass production of high-quality large-area 2D thin films. Here, we demonstrate a strategy for the automated manufacturing of high-quality 2D thin films using a modified drop-casting approach. Our approach is simple; by using an automated pipette, a dilute aqueous suspension is dropped onto a substrate heated on a hotplate, and controlled convection by Marangoni flow and liquid removal causes the nanosheets to come together to form a tile-like monolayer film in 1-2 min. Ti0.87O2 nanosheets are utilized as a model system for investigating the control parameters such as concentrations, suction speeds, and substrate temperatures. We perform the automated one-drop assembly of a range of 2D nanosheets (metal oxides, graphene oxide, and hexagonal boron nitride) and successfully fabricate various functional thin films in multilayered, heterostructured, and sub-micrometer-thick forms. Our deposition method enables on-demand large-size (>2 inchϕ) manufacturing of high-quality 2D thin films while reducing the time and sample consumption.

DOI： 10.1021/acsami.3c02250

Free-Standing Molecularly Thin Amorphous Silica Nanosheets 査読有り

Yamamoto, E; Fujihara, K; Takezaki, Y; Ito, K; Shi, Y; Kobayashi, M; Osada, M

SMALL 19 巻 ( 22 ) 頁： 2300022 - 2300022 2023年2月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Small

Recent progress in 2D materials has initiated new fields of molecularly thin amorphous materials with mysterious properties and structures. However, designed synthesis of molecularly thin amorphous silica still remains a challenge; whether free-standing molecularly thin amorphous silica nanosheets can exist is unclear. Here, this issue is addressed by using a new chemical protocol; solid-state surfactant lamellae with ordered alkyl-chain arrangements can serve as superior templates guiding free-standing amorphous silica nanosheets. Simple sonication of the lamellar hybrids allows exfoliation into monolayer amorphous silica nanosheets with 0.9 nm thickness. In addition, the nanosheets show the distinctive feature of high colloidal stability that enables atomic layer engineering of silica nanocoatings and dielectric nanofilms. The approach may shed new light on the properties and applications of old silica.

DOI： 10.1002/smll.202300022

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/smll.202300022

Molecularly Thin BaTiO3 Nanosheets with Stable Ferroelectric Response 査読有り

Kazuki Hagiwara, Ki Nam Byun, Shu Morita, Eisuke Yamamoto, Makoto Kobayashi, Xioyang Liu, Minoru Osada

Advanced Electronic Materials 2023年2月

Damage-free LED lithography for atomically thin 2D material devices 査読有り

Shi, Y; Taniguchi, T; Byun, KN; Kurimoto, D; Yamamoto, E; Kobayashi, M; Tsukagoshi, K; Osada, M

SCIENTIFIC REPORTS 13 巻 ( 1 ) 頁： 2583 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Desired electrode patterning on two-dimensional (2D) materials is a foremost step for realizing the full potentials of 2D materials in electronic devices. Here, we introduce an approach for damage-free, on-demand manufacturing of 2D material devices using light-emitting diode (LED) lithography. The advantage of this method lies in mild photolithography by simply combining an ordinary optical microscope with a commercially available LED projector; the low-energy red component is utilized for optical characterization and alignment of devices, whereas the high-energy blue component is utilized for photoresist exposure and development of personal computer designed electrode patterns. This method offers maskless, damage-free photolithography, which is particularly suitable for 2D materials that are sensitive to conventional lithography. We applied this LED lithography to device fabrication of selected nanosheets (MoS2, graphene oxides and RuO2), and achieved damage-free lithography of various patterned electrodes with feature sizes as small as 1–2 μm. The LED lithography offers a useful approach for cost-effective mild lithography without any costly instruments, high vacuum, or complex operation.

DOI： 10.1038/s41598-023-29281-w

その他リンク： https://www.nature.com/articles/s41598-023-29281-w

Improved Energy Storage Performance of PVDF Nanocapacitors by Utilizing 2D Inorganic Barrier Layers 査読有り

Byun, KN; Yamamoto, E; Kobayash, M; Osada, M

CHEMISTRY LETTERS 52 巻 ( 1 ) 頁： 51 - 54 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemistry Letters

We demonstrated a rational approach for designing highperformance polymer-based energy storage capacitors. Twodimensional paraelectric Ca2Nb3O10 nanosheets were deposited on a ferroelectric poly(vinylidene fluoride) (PVDF) film to form paraelectric/ferroelectric hetero-assemblies. Such an artificial structuring enabled tailoring of the breakdown strength and dielectric response, realizing an enhanced energy density (∼10 J cm-3) compared to pristine PVDF film (∼1 J cm-3).

DOI： 10.1246/cl.220466