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Ago Hiroki Last modified date：2024.04.09

Professor / Interdisciplinary Graduate School of Engineering Sciences
Faculty of Engineering Sciences


Graduate School
Department of Interdisciplinary Engineering Sciences
Interdisciplinary Graduate School of Engineering Sciences
Department of Interdisciplinary Engineering Sciences
Interdisciplinary Graduate School of Engineering Sciences
Undergraduate School
School of Engineering
Other Organization
Global Innovation Center


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Homepage
https://kyushu-u.elsevierpure.com/en/persons/hiroki-ago
　Reseacher Profiling Tool　Kyushu University Pure
http://www.gic.kyushu-u.ac.jp/ago/index-e.html
Research on growth, characterization, and various applications of graphene and related two-dimensional materials .
https://25d-materials.jp/en/
The homepage of the KAKENHI group research project, "Science of 2.5D Materials", which is lead by Prof. Ago. .
Academic Degree
Doctor of Engineering
Country of degree conferring institution (Overseas)
No
Field of Specialization
Nanotechnology, Molecular Engineering, Materials Science, Crystal Growth, Physical Chemistry
ORCID(Open Researcher and Contributor ID)
0000-0003-0908-5883
Total Priod of education and research career in the foreign country
01years05months
Outline Activities
Research activities:
Atom-thick, two-dimensional materials, represented by graphene, have attracted great interest because of their excellent electronic, mechanical, and optoelectronic properties. Furthermore, recent development of graphene stimulated the research on new two-dimensional nanomaterials, such as hexagonal boron nitride and transition metal chalcogenides. We are developing the 2D materials research regarding the following topics:

[1] Production of extremely high-quality monolayer graphene in large size
[2] Development of CVD synthesis and applications of bilayer graphene
[3] Research development of hexagonal boron nitride
[4] Research development of transition metal chalcogenides and related heterostructures
[5] Investigation of various nanostructures and novel functions
[6] Establish the open innovation network of 2D materials (KOINE)
In addition to the above projects, as a cross-appointment fellow of AIST, Tsukuba, the industrial applications of graphene has been developed recently.

Education activities:
Teaching in classes in the graduate school.

Others:
Contributing to GCOE Program and Kyushu University Program for Leading Graduate Schools.
Research
Research Interests
  • Novel transfer of 2D materials with functional tapes
    keyword : 2D materials
    2018.04.
  • Science and functions of two-dimensional nanospace
    keyword : 2D materials
    2018.04～2024.05.
  • Research on atomic layers of hexagonal boron nitride
    keyword : hexagonal boron nitride
    2016.04.
  • Research on atomic layers of transition metal chalcogenides
    keyword : transition metal chalcogenides
    2016.04.
  • Synthesis of novel carbon materials
    keyword : nanocarbon
    2012.04～2018.03.
  • Growth and Development of new two-dimensional materials
    keyword : two-dimensional materials
    2012.04.
  • Electronic and optical properties of graphene and development of electronic applications
    keyword : graphene, CVD, physical properties devices
    2011.04Study on the formation processes of carbon nanotubes and applied them to the control of the nanotube structure..
  • Development of processing methods of graphene
    keyword : graphene, CVD, processing
    2010.04～2018.03Study on the formation processes of carbon nanotubes and applied them to the control of the nanotube structure..
  • Catalytic growth of graphene films and understanding the growth mechanism
    keyword : graphene, cystal growth, CVD
    2011.04Study on the formation processes of carbon nanotubes and applied them to the control of the nanotube structure..
  • Development of highly controlled synthesis of single-walled carbon nanotubes - chirality/electronic structure control-
    keyword : carbon nanotube, chirality, semiconductor
    2007.10～2016.03.
  • Epitaxially aligned growth and high-density growth of single-walled carbon nanotubes
    keyword : single-walled carbon nanotubes, horizontally-aligned growth
    2004.10～2016.03Epitaxial aligned growth of single-walled carbon nanotubes.
  • Basic research for electronic applications of single-walled carbon nanotubes
    keyword : carbon nanotubes, transistors
    2005.04～2012.03Device applications of single-walled carbon nanotubes.
Current and Past Project
  • PRESTO-JST "Synthesis and Nanoelectronics of Two-Dimensional Integrated Atomic Layers"
  • Synthesis and Control of Graphene for Carbon Electronics
  • Synthesis and Control of Graphene for Carbon Electronics
  • Epitaxial growth of single-walled carbon nanotubes on crystalline surfaces.
  • Fabrication of ordered carbon nanotube network and application to next-generation semiconductor devices.
Academic Activities
Books
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1. Pablo Solis Fernandez, Hiroki Ago, Encyclopedia of Condensed Matter Physics (2nd edition), Elsevier, 2023.11.
2. Hiroki Ago, Frontiers of Graphene and Carbon Nanotubes: Devices and Applications, Springer, CVD Growth of High-Quality Single-Layer Graphene, 2015.04.
3. Carbon Nanotubes - Challenge to nanodevices -
Chap. 11; Workfunction and integrated devices with semiconductors, H. Ago
K. Tanaka ed..
4. H. Ago and T. Yamabe, The Science and Technology of Carbon Nanotubes, Elsevier Science, Oxford, UK, Frontiers in Carbon Nanotubes and Beyond, Chap. 14, p.163-183, 1999.01.
Reports
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Papers
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1. M. Nakatani, S. Fukamachi, P. Solís-Fernández, S. Honda, M. Harada, K. Kawahara, Y. Tsuji, Y. Sumiya, M. Kuroki, K. Li, Q. Liu, Y.-C. Lin, A. Uchida, S. Oyama, H. Ji, K. Okada, K. Suenaga, Y. Kawano, K. Yoshizawa, A. Yasui, H. Ago, Ready-to-transfer two-dimensional materials using tunable adhesive force tapes, Nature Electronics, 10.1038/s41928-024-01121-3, 7, 119, 2024.02, [URL].
2. Y.-C. Lin*, R. Matsumoto, Q. Liu, P. Soslís-Fernández, M.-D. Siao, P.-W. Chiu, H. Ago, K. Suenaga, Alkali metal bilayer intercalation in graphene, Nature Communications, 10.1038/s41467-023-44602-3, 15, 425, 2024.01, [URL].
3. C. J. Knill*, S. Douyon, K. Kawahara, H. Yamaguchi, G. Wang, H. Ago, N. Moody, S. Karkare, Effects of nonlinear photoemission on mean transverse energy from metal photocathodes, ACS Nano, 10.1021/acsnano.3c06958, 17, 23659, 2023.11.
4. D. Inukai, T. Koyama, K. Kawahara, H. Ago, H. Kishida, Complex third-order nonlinear susceptibility of single-layer graphene governing third-harmonic generation, Phys. Rev. B, 10.1103/PhysRevB.108.075408, 108, 075408 , 2023.08.
5. S. Hirokawa, H. Teshima, H. Kawamoto, P. Solis-Fernandez, H. Ago, Q. Y. Li, K. Takahashi, Random but limited pressure of graphene liquid cells, Ultramicroscopy, 10.1016/j.ultramic.2023.113747, 250, 113747 , 2023.04.
6. S. Fukamachi, P. Solis-Fernandez, K. Kawahara, D. Tanaka, T. Ohtake, Y.-C. Lin, K. Suenaga, H. Ago, Large-area synthesis and transfer of multilayer hexagonal boron nitride for enhanced graphene device arrays, Nature Electronics, 10.1038/s41928-022-00911-x, 6, 126-136, 2023.02, [URL], Multilayer hexagonal boron nitride (hBN) can be used to preserve the intrinsic physical properties of other two-dimensional materials in device structures. However, integrating the material into large-scale two-dimensional heterostructures remains challenging due to the difficulties in synthesizing high-quality large-area multilayer hBN and combining it with other two-dimensional material layers of the same scale. Here we show that centimetre-scale multilayer hBN can be synthesized on iron–nickel alloy foil by chemical vapour deposition, and then used as a substrate and as a surface-protecting layer in graphene field-effect transistors. We also develop an integrated electrochemical transfer and thermal treatment method that allows us to create high-performance graphene/hBN heterostacks. Arrays of graphene field-effect transistors fabricated by conventional and scalable methods show an enhancement in room-temperature carrier mobility when hBN is used as an insulating substrate, and a further increase—up to a value of 10,000 cm2 V−1 s−1—when graphene is encapsulated with another hBN sheet..
7. H.-L. Liu, B. D. Annawati, N. T. Hung, D. P. Gulo, P. Solis-Fernandez, K. Kawahara, H. Ago, R. Saito, Interference of excitons and surface plasmons in the optical absorption spectra of monolayer and bilayer graphene, Phys. Rev. B, 10.1103/PhysRevB.107.165421, 107, 165421, 2023.03.
8. C. J. Knill, H. Yamaguchi, K. Kawahara, G. Wang, E. Batista, P. Yang, H. Ago, N. Moody, S. Karkare, Near-Threshold Photoemission from Graphene-Coated Cu(110), Phys. Rev. Appl., 10.1103/PhysRevApplied.19.014015, 19, 014015 , 2023.01.
9. T. Vincent, K. Kawahara, V. Antonov, H. Ago, O. Kazakova, Data cluster analysis and machine learning for classification of twisted bilayer graphene, Carbon, 10.1016/j.carbon.2022.09.021, 201, 141-149, 2023.01.
10. Y. Hsin, P. Solís-Fernández, H. Hibino, H. Ago, Surface etching and edge control of hexagonal boron nitride assisted by triangular Sn nanoplates, Nanoscale Adv., 10.1039/D2NA00479H, 4, 3786-3792 ,
, 2022.08.
11. Y. Araki, P. Solís-Fernández, Y.-C. Lin, A. Motoyama, K. Kawahara, M. Maruyama, G. Yanlin, R. Matsumoto, K. Suenaga, S. Okada, H. Ago, Twist angle-dependent molecular intercalation and sheet resistance in bilayer graphene, ACS Nano, 10.1021/acsnano.2c03997, 16, 9, 14075-14085 , 2022.08.
12. P. Solis-Fernandez, H. Ago, Machine learning determination of the twist angle of bilayer graphene by Raman spectroscopy: Implications for van der Waals heterostructures, ACS Appl. Nano Mater., 10.1021/acsanm.1c03928, 5, 1, 356-1366, 2022.01.
13. R. Das, P. Solís-Fernández, D. Breite, A. Prager, A. Lotnyk, A. Schulze, H. Ago, High flux and adsorption based non-functionalized hexagonal boron nitride lamellar membrane for ultrafast water purification, Chem. Eng. J., 10.1016/j.cej.2020.127721, 420, 2, 127721, 2021.09.
14. Y.-C. Lin, A. Motoyama, S. Kretschmer, S. Ghaderzadeh, M. Ghorbani-Asl, Y. Araki, A. V. Krasheninnikov, H. Ago, K. Suenaga, Polymorphic Phases of Metal Chlorides in the Confined 2D Space of Bilayer Graphene, Adv. Mater., 10.1002/adma.202105898, 33, 52, 2105898, 2021.10.
15. Y.-C. Lin, A. Motoyama, R. Matsumoto, H. Ago, K. Suenaga, Coupling and Decoupling of Bilayer Graphene Monitored by Electron Energy Loss Spectroscopy, Nano Lett., 10.1021/acs.nanolett.1c03689, 21, 24, 10386-10391, 2021.12.
16. H. Ago, S. Okada, Y. Miyata, K. Matsuda, M. Koshino, K. Ueno, K. Nagashio, Science of 2.5 dimensional materials: paradigm shift of materials science toward future social innovation, Sci. Tech. Adv. Mater., 10.1080/14686996.2022.2062576, 23, 1, 275-299, 2022.02.
17. H. G. Ji, U. Erkılıç, P. Solís-Fernández, H. Ago, Stacking orientation-dependent photoluminescence pathways in artificially stacked bilayer WS2 nanosheets grown by chemical vapor deposition: Implications for spintronics and valleytronics, ACS Applied Nano Materials, 10.1021/acsanm.1c00192, 3717-3724, 2021.03.
18. Y. Uchida, K. Kawahara, S. Fukamachi, H. Ago, Chemical Vapor deposition growth of uniform multilayer hexagonal boron nitride driven by structural transformation of metal thin film, ACS Applied Electronic Materials, 10.1021/acsaelm.0c00601, 3270-3278, 2020.09.
19. U. Erkılıç, H. G. Ji, E. Nishibori, H. Ago, One-step vapour phase growth of two-dimensional formamidinium-based perovskite and its hot carrier dynamics, Physical Chemistry Chemical Physics, 10.1039/D0CP02652B, 21512-21519, 2020.08.
20. P. Solís-Fernández, Y. Terao, K. Kawahara, W. Nishiyama, T. Uwanno, Y.-C. Li, K. Yamamoto, H. Nakashima, K. Nagashio, H. Hibino, K. Suenaga, H. Ago, Isothermal Growth and Stacking Evolution in Highly Uniform Bernal-Stacked Bilayer Graphene, ACS Nano, 10.1021/acsnano.0c00645, 2020.05.
21. Alexandre Budiman Taslim, Hideaki Nakajima, Yung Chang Lin, Yuki Uchida, Kenji Kawahara, Toshiya Okazaki, Kazu Suenaga, Hiroki Hibino, Hiroki Ago, Synthesis of sub-millimeter single-crystal grains of aligned hexagonal boron nitride on an epitaxial Ni film, Nanoscale, 10.1039/c9nr03525g, 11, 31, 14668-14675, 2019.08, Hexagonal boron nitride (h-BN), an insulating two-dimensional (2D) layered material, has attracted increasing interest due to its electrical screening effect, high-temperature-resistant gas barrier properties, and other unique applications. However, the presence of grain boundaries (GBs) in h-BN is a hindrance to obtain these properties. Here, we demonstrate the epitaxial growth of monolayer h-BN by chemical vapor deposition (CVD) on Ni(111) thin films deposited on c-plane sapphire. The Ni(111) films showed higher thermal stability than Cu(111) and Cu-Ni(111) alloy films, allowing us to perform CVD growth at a high temperature of 1100 °C. This resulted in an increase of the h-BN grain sizes to up to 0.5 millimeter, among the highest reported so far, and in a well-defined triangular grain shape. Low-energy electron microscopy (LEEM) revealed the epitaxial relationship between h-BN and the underlying Ni(111) lattice, leading to a preferential alignment of the h-BN grains. Both the large grain size and the alignment are expected to facilitate the synthesis of h-BN with a low density of GBs. We also found that the addition of N2 gas during the CVD improves the crystalline shape of the h-BN grains, changing from an irregular, truncated to a sharp triangle. The growth behavior of monolayer h-BN is further discussed in terms of the dependences on growth temperature and pressure, as well as on the structural evolution of the Ni metal catalyst. Our findings not only help understand the h-BN growth mechanism but also offer a new route to grow high-quality, monolayer h-BN films..
22. Hyun Goo Ji, Pablo Solís-Fernández, Daisuke Yoshimura, Mina Maruyama, Takahiko Endo, Yasumitsu Miyata, Susumu Okada, Hiroki Ago, Chemically Tuned p- and n-Type WSe2 Monolayers with High Carrier Mobility for Advanced Electronics, Advanced Materials, 10.1002/adma.201903613, 31, 42, 2019.10, Monolayers of transition metal dichalcogenides (TMDCs) have attracted a great interest for post-silicon electronics and photonics due to their high carrier mobility, tunable bandgap, and atom-thick 2D structure. With the analogy to conventional silicon electronics, establishing a method to convert TMDC to p- and n-type semiconductors is essential for various device applications, such as complementary metal-oxide-semiconductor (CMOS) circuits and photovoltaics. Here, a successful control of the electrical polarity of monolayer WSe2 is demonstrated by chemical doping. Two different molecules, 4-nitrobenzenediazonium tetrafluoroborate and diethylenetriamine, are utilized to convert ambipolar WSe2 field-effect transistors (FETs) to p- and n-type, respectively. Moreover, the chemically doped WSe2 show increased effective carrier mobilities of 82 and 25 cm2 V−1s−1 for holes and electrons, respectively, which are much higher than those of the pristine WSe2. The doping effects are studied by photoluminescence, Raman, X-ray photoelectron spectroscopy, and density functional theory. Chemically tuned WSe2 FETs are integrated into CMOS inverters, exhibiting extremely low power consumption (≈0.17 nW). Furthermore, a p-n junction within single WSe2 grain is realized via spatially controlled chemical doping. The chemical doping method for controlling the transport properties of WSe2 will contribute to the development of TMDC-based advanced electronics..
23. Yuki Uchida, Sho Nakandakari, Kenji Kawahara, Shigeto Yamasaki, Masatoshi Mitsuhara, Hiroki Ago, Controlled Growth of Large-Area Uniform Multilayer Hexagonal Boron Nitride as an Effective 2D Substrate, ACS nano, 10.1021/acsnano.8b03055, 12, 6, 6236-6244, 2018.06, Multilayer hexagonal boron nitride (h-BN) is an ideal insulator for two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, because h-BN screens out influences from surroundings, allowing one to observe intrinsic physical properties of the 2D materials. However, the synthesis of large and uniform multilayer h-BN is still very challenging because it is difficult to control the segregation process of B and N atoms from metal catalysts during chemical vapor deposition (CVD) growth. Here, we demonstrate CVD growth of multilayer h-BN with high uniformity by using the Ni-Fe alloy film and borazine (B3H6N3) as catalyst and precursor, respectively. Combining Ni and Fe metals tunes the solubilities of B and N atoms and, at the same time, allows one to engineer the metal crystallinity, which stimulates the uniform segregation of multilayer h-BN. Furthermore, we demonstrate that triangular WS2 grains grown on the h-BN show photoluminescence stronger than that grown on a bare SiO2 substrate. The PL line width of WS2/h-BN (the minimum and mean widths are 24 and 43 meV, respectively) is much narrower than those of WS2/SiO2 (44 and 67 meV), indicating the effectiveness of our CVD-grown multilayer h-BN as an insulating layer. Large-area, multilayer h-BN realized in this work will provide an excellent platform for developing practical applications of 2D materials..
24. Kenshiro Suenaga, Hyun Goo Ji, Yung Chang Lin, Tom Vincent, Mina Maruyama, Adha Sukma Aji, Yoshihiro Shiratsuchi, Dong Ding, Kenji Kawahara, Susumu Okada, Vishal Panchal, Olga Kazakova, Hiroki Hibino, Kazu Suenaga, Hiroki Ago, Surface-Mediated Aligned Growth of Monolayer MoS2 and In-Plane Heterostructures with Graphene on Sapphire, ACS nano, 10.1021/acsnano.8b04612, 2018.01, Aligned growth of transition metal dichalcogenides and related two-dimensional (2D) materials is essential for the synthesis of high-quality 2D films due to effective stitching of merging grains. Here, we demonstrate the controlled growth of highly aligned molybdenum disulfide (MoS2) on c-plane sapphire with two distinct orientations, which are highly controlled by tuning sulfur concentration. We found that the size of the aligned MoS2 grains is smaller and their photoluminescence is weaker as compared with those of the randomly oriented grains, signifying enhanced MoS2-substrate interaction in the aligned grains. This interaction induces strain in the aligned MoS2, which can be recognized from their high susceptibility to air oxidation. The surface-mediated MoS2 growth on sapphire was further developed to the rational synthesis of an in-plane MoS2-graphene heterostructure connected with the predefined orientation. The in-plane epitaxy was observed by low-energy electron microscopy. Transmission electron microscopy and scanning transmission electron microscopy suggest the alignment of a zigzag edge of MoS2 parallel to a zigzag edge of the neighboring graphene. Moreover, better electrical contact to MoS2 was obtained by the monolayer graphene compared with a conventional metal electrode. Our findings deepen the understanding of the chemical vapor deposition growth of 2D materials and also contribute to the tailored synthesis as well as applications of advanced 2D heterostructures..
25. Y. Miyoshi, Y. Fukazawa, Y. Amasaka, R. Reckmann, T. Yokoi, K. Ishida, K. Kawahara, H. Ago, H. Maki, High-speed and on-chip graphene blackbody emitters for optical communications by remote heat transfer, Nature Communications, 1279, 2018.03.
26. Hyun Goo Ji, Yung Chang Lin, Kosuke Nagashio, Mina Maruyama, Pablo Solís-Fernández, Adha Sukma Aji, Vishal Panchal, Susumu Okada, Kazu Suenaga, Hiroki Ago, Hydrogen-Assisted Epitaxial Growth of Monolayer Tungsten Disulfide and Seamless Grain Stitching, Chemistry of Materials, 10.1021/acs.chemmater.7b04149, 30, 2, 403-411, 2018.01, Recently, research on transition metal dichalcogenides (TMDCs) has been accelerated by the development of large-scale synthesis based on chemical vapor deposition (CVD). However, in most cases, CVD-grown TMDC sheets are composed of randomly oriented grains, and thus contain many distorted grain boundaries (GBs) which deteriorate the physical properties of the TMDC. Here, we demonstrate the epitaxial growth of monolayer tungsten disulfide (WS2) on sapphire by introducing a high concentration of hydrogen during the CVD process. As opposed to the randomly oriented grains obtained in conventional growth, the presence of H2 resulted in the formation of triangular WS2 grains with the well-defined orientation determined by the underlying sapphire substrate. Photoluminescence of the aligned WS2 grains was significantly suppressed compared to that of the randomly oriented grains, indicating a hydrogen-induced strong coupling between WS2 and the sapphire surface that has been confirmed by density functional theory calculations. Scanning transmission electron microscope observations revealed that the epitaxially grown WS2 has less structural defects and impurities. Furthermore, sparsely distributed unique dislocations were observed between merging aligned grains, indicating an effective stitching of the merged grains. This contrasts with the GBs that are observed between randomly oriented grains, which include a series of 8-, 7-, and alternating 7/5-membered rings along the GB. The GB structures were also found to have a strong impact on the chemical stability and carrier transport of merged WS2 grains. Our work offers a novel method to grow high-quality TMDC sheets with much less structural defects, contributing to the future development of TMDC-based electronic and photonic applications..
27. Adha Sukma Aji, Masanori Izumoto, Kenshiro Suenaga, Keisuke Yamamoto, Hiroshi Nakashima, Hiroki Ago, Two-step synthesis and characterization of vertically stacked SnS-WS2 and SnS-MoS2 p-n heterojunctions, Physical Chemistry Chemical Physics, 10.1039/c7cp06823a, 20, 2, 889-897, 2018.01, We demonstrate the synthesis of unique heterostructures consisting of SnS and WS2 (or SnS and MoS2) by two-step chemical vapor deposition (CVD). After the first CVD growth of triangular WS2 (MoS2) grains, the second CVD step was performed to grow square SnS grains on the same substrate. We found that these SnS grains can be grown at very low temperature with the substrate temperature of 200 °C. Most of the SnS grains nucleated from the side edges of WS2 (MoS2) grains, resulting in the formation of partly stacked heterostructures with a large overlapping area. The SnS grains showed doped p-type transfer character with a hole mobility of 15 cm2 V-1 s-1, while the WS2 and MoS2 grains displayed n-type character with a high on/off ratio of >106. The SnS-WS2 and SnS-MoS2 heterostructures exhibited clear rectifying behavior, signifying the formation of p-n junctions at their interfaces. This heterostructure growth combined with the low temperature SnS growth will provide a promising means to exploit two-dimensional heterostructures by avoiding possible damage to the first material..
28. Adha Sukma Aji, Pablo Solís-Fernández, Hyun Goo Ji, Kenjiro Fukuda, Hiroki Ago, High Mobility WS2 Transistors Realized by Multilayer Graphene Electrodes and Application to High Responsivity Flexible Photodetectors, Advanced Functional Materials, 10.1002/adfm.201703448, 27, 47, 2017.12, The electrical contact is one of the main issues preventing semiconducting 2D materials to fulfill their potential in electronic and optoelectronic devices. To overcome this problem, a new approach is developed here that uses chemical vapor deposition grown multilayer graphene (MLG) sheets as flexible electrodes for WS2 field-effect transistors. The gate-tunable Fermi level, van der Waals interaction with the WS2, and the high electrical conductivity of MLG significantly improve the overall performance of the devices. The carrier mobility of single-layer WS2 increases about a tenfold (50 cm2 V−1 s−1 at room temperature) by replacing conventional Ti/Au metal electrodes (5 cm2 V−1 s−1) with the MLG electrodes. Further, by replacing the conventional SiO2 substrate with a thin (1 µm) parylene-C flexible film as insulator, flexible WS2 photodetectors that are able to sustain multiple bending stress tests without significant performance degradation are realized. The flexible photodetectors exhibited extraordinarily high gate-tunable photoresponsivities, reaching values of 4500 A W−1, and with very short (2, graphene, and the very thin polymer film will find applications in various flexible electronics, such as wearable high-performance optoelectronics devices..
29. Hiroki Kinoshita, Il Jeon, Mina Maruyama, Kenji Kawahara, Yuri Terao, Dong Ding, Rika Matsumoto, Yutaka Matsuo, Susumu Okada, Hiroki Ago, Highly Conductive and Transparent Large-Area Bilayer Graphene Realized by MoCl5 Intercalation, Advanced Materials, 10.1002/adma.201702141, 29, 41, 2017.11, Bilayer graphene (BLG) comprises a 2D nanospace sandwiched by two parallel graphene sheets that can be used to intercalate molecules or ions for attaining novel functionalities. However, intercalation is mostly demonstrated with small, exfoliated graphene flakes. This study demonstrates intercalation of molybdenum chloride (MoCl5) into a large-area, uniform BLG sheet, which is grown by chemical vapor deposition (CVD). This study reveals that the degree of MoCl5 intercalation strongly depends on the stacking order of the graphene; twist-stacked graphene shows a much higher degree of intercalation than AB-stacked. Density functional theory calculations suggest that weak interlayer coupling in the twist-stacked graphene contributes to the effective intercalation. By selectively synthesizing twist-rich BLG films through control of the CVD conditions, low sheet resistance (83 Ω ▫−1) is realized after MoCl5 intercalation, while maintaining high optical transmittance (≈95%). The low sheet resistance state is relatively stable in air for more than three months. Furthermore, the intercalated BLG film is applied to organic solar cells, realizing a high power conversion efficiency..
30. Pablo Solís-Fernández, Mark Bissett, Hiroki Ago, Synthesis, structure and applications of graphene-based 2D heterostructures, Chemical Society Reviews, 10.1039/c7cs00160f, 46, 15, 4572-4613, 2017.08, With the profuse amount of two-dimensional (2D) materials discovered and the improvements in their synthesis and handling, the field of 2D heterostructures has gained increased interest in recent years. Such heterostructures not only overcome the inherent limitations of each of the materials, but also allow the realization of novel properties by their proper combination. The physical and mechanical properties of graphene mean it has a prominent place in the area of 2D heterostructures. In this review, we will discuss the evolution and current state in the synthesis and applications of graphene-based 2D heterostructures. In addition to stacked and in-plane heterostructures with other 2D materials and their potential applications, we will also cover heterostructures realized with lower dimensionality materials, along with intercalation in few-layer graphene as a special case of a heterostructure. Finally, graphene heterostructures produced using liquid phase exfoliation techniques and their applications to energy storage will be reviewed..
31. Yuki Uchida, Tasuku Iwaizako, Seigi Mizuno, Masaharu Tsuji, Hiroki Ago, Epitaxial chemical vapour deposition growth of monolayer hexagonal boron nitride on a Cu(111)/sapphire substrate, Physical Chemistry Chemical Physics, 10.1039/c6cp08903h, 19, 12, 8230-8235, 2017.02, Hexagonal boron nitride (h-BN), an atomically thin insulating material, shows a large band gap, mechanical flexibility, and optical transparency. It can be stacked with other two-dimensional (2D) materials through van der Waals interactions to form layered heterostructures. These properties promise its application as an insulating layer of novel 2D electronic devices due to its atomically smooth surface with a large band gap. Herein, we demonstrated the ambient-pressure chemical vapour deposition (CVD) growth of high-quality, large-area monolayer h-BN on a Cu(111) thin film deposited on a c-plane sapphire using ammonia borane (BH3NH3) as the feedstock. Highly oriented triangular h-BN grains grow on Cu(111), which finally coalescence to cover the entire Cu surface. Low-energy electron diffraction (LEED) measurements indicated that the hexagonal lattice of the monolayer h-BN is well-oriented along the underlying Cu(111) lattice, thus implying the epitaxial growth of h-BN, which can be applied in various 2D electronic devices..
32. Dong Ding, Pablo Solís-Fernández, Hiroki Hibino, Hiroki Ago, Spatially Controlled Nucleation of Single-Crystal Graphene on Cu Assisted by Stacked Ni, ACS Nano, 10.1021/acsnano.6b06265, 10, 12, 11196-11204, 2016.12, In spite of recent progress of graphene growth using chemical vapor deposition, it is still a challenge to precisely control the nucleation site of graphene for the development of wafer-scale single-crystal graphene. In addition, the postgrowth patterning used for device fabrication deteriorates the quality of graphene. Herein we demonstrate the site-selective nucleation of single-crystal graphene on Cu foil based on spatial control of the local CH4 concentration by a perforated Ni foil. The catalytically active Ni foil acts as a CH4 modulator, resulting in millimeter-scale single-crystal grains at desired positions. The perforated Ni foil also allows to synthesize patterned graphene without any postgrowth processing. Furthermore, the uniformity of monolayer graphene is significantly improved when a plain Ni foil is placed below the Cu. Our findings offer a facile and effective way to control the nucleation of high-quality graphene, meeting the requirements of industrial processing..
33. Yuichiro Takesaki, Kenji Kawahara, Hiroki Hibino, Susumu Okada, Masaharu Tsuji, Hiroki Ago, Highly Uniform Bilayer Graphene on Epitaxial Cu-Ni(111) Alloy, Chemistry of Materials, 10.1021/acs.chemmater.6b01137, 28, 13, 4583-4592, 2016.07, Band gap opening in bilayer graphene (BLG) under a vertical electric field is important for the realization of high performance graphene-based semiconductor devices, and thus, the synthesis of uniform and large-area BLG is required. Here we demonstrate the synthesis of a highly uniform BLG film by chemical vapor deposition (CVD) over epitaxial Cu-Ni (111) binary alloy catalysts. The relative concentration of Ni and Cu as well as the growth temperature and cooling profile was found to strongly influence the uniformity of the BLG. In particular, a slow cooling process after switching off the carbon feedstock is important for obtaining a uniform second layer, covering more than 90% of the total area. Moreover, low-energy electron microscopy (LEEM) study revealed the second layer grows underneath the first layer. We also investigated the stacking order by Raman spectroscopy and LEEM and found that 70-80% of bilayer graphene has Bernal stacking. The metastable 30°-rotated orientations were also observed both in the upper and lower layers. From our experimental observations, a new growth mode is proposed; the first layer grows during the CH4 supply on Cu-Ni alloy surface, while the second layer is segregated from the bulk alloy during the cooling process. Our work highlights the growth mechanism of BLG and offers a promising route to synthesize uniform and large-area BLG for future electronic devices..
34. Hiroki Ago, Satoru Fukamachi, Hiroko Endo, Pablo Solís-Fernández, Rozan Mohamad Yunus, Yuki Uchida, Vishal Panchal, Olga Kazakova, Masaharu Tsuji, Visualization of Grain Structure and Boundaries of Polycrystalline Graphene and Two-Dimensional Materials by Epitaxial Growth of Transition Metal Dichalcogenides, ACS Nano, 10.1021/acsnano.5b05879, 10, 3, 3233-3240, 2016.03, The presence of grain boundaries in two-dimensional (2D) materials is known to greatly affect their physical, electrical, and chemical properties. Given the difficulty in growing perfect large single-crystals of 2D materials, revealing the presence and characteristics of grain boundaries becomes an important issue for practical applications. Here, we present a method to visualize the grain structure and boundaries of 2D materials by epitaxially growing transition metal dichalcogenides (TMDCs) over them. Triangular single-crystals of molybdenum disulfide (MoS2) epitaxially grown on the surface of graphene allowed us to determine the orientation and size of the graphene grains. Grain boundaries in the polycrystalline graphene were also visualized reflecting their higher chemical reactivity than the basal plane. The method was successfully applied to graphene field-effect transistors, revealing the actual grain structures of the graphene channels. Moreover, we demonstrate that this method can be extended to determine the grain structure of other 2D materials, such as tungsten disulfide (WS2). Our visualization method based on van der Waals epitaxy can offer a facile and large-scale labeling technique to investigate the grain structures of various 2D materials, and it will also contribute to understand the relationship between their grain structure and physical properties..
35. Pablo Solís-Fernández, Susumu Okada, Tohru Sato, Masaharu Tsuji, Hiroki Ago, Gate-Tunable Dirac Point of Molecular Doped Graphene, ACS Nano, 10.1021/acsnano.6b00064, 10, 2, 2930-2939, 2016.02, Control of the type and density of charge carriers in graphene is essential for its implementation into various practical applications. Here, we demonstrate the gate-tunable doping effect of adsorbed piperidine on graphene. By gradually increasing the amount of adsorbed piperidine, the graphene doping level can be varied from p-to n-type, with the formation of p-n junctions for intermediate coverages. Moreover, the doping effect of the piperidine can be further tuned by the application of large negative back-gate voltages, which increase the doping level of graphene. In addition, the electronic properties of graphene are well preserved due to the noncovalent nature of the interaction between piperidine and graphene. This gate-tunable doping offers an easy, controllable, and nonintrusive method to alter the electronic structure of graphene..
36. Rozan M. Yunus, Hiroko Endo, Masaharu Tsuji, Hiroki Ago, Vertical heterostructure of MoS2 and graphene nanoribbons by two-step chemical vapor deposition for high-gain photodetectors, Physical Chemistry Chemical Physics, 17, 25210-25215, 2015.09.
37. Hiroki Ago, Yujiro Ohta, Hiroki Hibino, Daisuke Yoshimuara, Rina Takizawa, Yuki Uchida, Masaharu Tsuji, Toshihiro Okajima, Hisashi Mitani, Seigi Mizuno, Growth Dynamics of Single-Layer Graphene on Epitaxial Cu Surfaces, CHEMISTRY OF MATERIALS, 10.1021/acs.chemmater.5b01871, 27, 15, 5377-5385, 2015.08.
38. Hiroki Ago, Hiroko Endo, SOLIS FERNANDEZ PABLO, Rina Takizawa, Yujiro Ohta, Yusuke Fujita, Kazuhiro Yamamoto, Masaharu Tsuji, Controlled van der Waals Epitaxy of Monolayer MoS2 Triangular Domains on Graphene, ACS Applied Materials & Interfaces, 7, 9, 5265-5273, 2015.02.
39. Hiroki Ago, Rozan M. Yunus, Masahiro Miyashita, SOLIS FERNANDEZ PABLO, Masaharu Tsuji, Hiroki Hibino, Formation of Oriented Graphene Nanoribbons over Heteroepitaxial Cu Surfaces by Chemical Vapor Deposition, CHEMISTRY OF MATERIALS, 10.1021/cm501854r, 26, 18, 5215-5222 , 2014.09.
40. Yui Ogawa, Katsuyoshi Komatsu, Kenji Kawahara, Masaharu Tsuji, Kazuhito Tsukagoshi, Hiroki Ago, Structure and transport properties of the interface between CVD-grown graphene domains, Nanoscale, 6, 13, 7288-7294, 2014.07.
41. Hiroki Ago, Izumi Tanaka, Yui Ogawa, Rozan M. Yunus, Masaharu Tsuji, Hiroki Hibino, Strain Engineering the Properties of Graphene and Other Two-Dimensional Crystals, ACS Nano, 10825-10833, 2014.04.
42. Hiroki Ago, Izumi Tanaka, Yui Ogawa, Rozan M. Yunus, Masaharu Tsuji, Hiroki Hibino, Lattice-oriented catalytic growth of graphene nanoribbons on heteroepitaxial nickel films, ACS Nano, 7, 12, 10825-10833, 2013.12.
43. MARK ALEXANDER BISSETT, Satoru Konabe, Susumu Okada, Masaharu Tsuji, Hiroki Ago, Enhanced chemical reactivity of graphene induced by mechanical strain, ACS Nano, 7, 11, 10335-10343, 2013.11.
44. SOLIS FERNANDEZ PABLO, Kazuma Yoshida, Yui Ogawa, Masaharu Tsuji, Hiroki Ago, Dense arrays of highly aligned graphene nanoribbons produced by substrate-controlled metal-assisted etching of graphene, Advanced Materials, 25, 45, 6562-6568, 2013.12.
45. Hiroki Ago, Kenji Kawahara, Yui Ogawa, Shota Tanoue, MARK ALEXANDER BISSETT, Masaharu Tsuji, Hidetsugu Sakaguchi, Roland J. Koch, Felix Fromm, Thomas Seyller, Katsuyoshi Komatsu, Kazuhito Tsukagoshi, Epitaxial growth and electronic properties of large hexagonal graphene domains on Cu(111) thin film, Applied Physics Express, 6, 7, 75101-1-75101-4, 2013.07.
46. MARK ALEXANDER BISSETT, Wataru Izumida, Riichiro Saito, Hiroki Ago, Effect of domain boundaries on the Raman spectra of mechanically strained graphene, ACS Nano, 6, 11, 10229-10238, 2012.10.
47. Hiroki Ago, Yui Ogawa, Masaharu Tsuji, Seigi Mizuno, Hiroki Hibino, Catalytic growth of graphene: towards large-area single-crystalline graphene, J. Phys. Chem. Lett., 3, 16, 2228-2236, 2012.08.
48. Hiroki Ago, Yoshito Ito, Masaharu Tsuji, Ken-ichi Ikeda, Step-templated CVD growth of aligned graphene nanoribbons supported by single-layer graphene film, Nanoscale, 4, 16, 5178-5182, 2012.08.
49. Y. Ogawa, B. Hu, C. M. Orofeo, M. Tsuji, K. Ikeda, S. Mizuno, H. Hibino, H. Ago, Domain structure and boundary in single-layer graphene grown on Cu (111) and Cu (100) films, J. Phys. Chem. Lett., 3, 2, 219-226, 2012.01.
50. B. Hu, H. Ago,* Y. Ito, K. Kawahara, M. Tsuji, E. Magome, K. Sumitani, N. Mizuta, K. Ikeda, S. Mizuno, Epitaxial growth of large-area single-layer graphene over Cu(111)/sapphire by atmospheric pressure CVD, Carbon, 50, 1, 57-65, 2012.01.
51. H. Ago, T. Ayagaki, Y. Ogawa, M. Tsuji, Ultra-high vacuum-assisted control of metal nanoparticles for horizontally-aligned single-walled carbon nanotubes with extraordinary uniform diameters, J. Phys. Chem. C, 115, 27, 13247-13253, 2011.07.
52. C. M. Orofeo, H. Ago, B. Hu, M. Tsuji, Synthesis of large-area, homogeneous, single layer graphene by annealing amorphous carbon on Co and Ni, Nano Res., 4, 6, 531-540, 2011.06.
53. H. Ago, Y. Ito, N. Mizuta, K. Yoshida, B. Hu, C. M. Orofeo, M. Tsuji, K. Ikeda, S. Mizuno, Epitaxial chemical vapor deposition growth of single-layer graphene over cobalt film crystallized on sapphire, ACS Nano, 4, 12, 7407-7414, 2010.12.
54. H. Ago, T. Nishi, K. Imamoto, N. Ishigami, M. Tsuji, T. Ikuta, K. Takahashi , Orthogonal growth of horizontally-aligned single-walled carbon nanotube arrays, J. Phys. Chem. C, 114, 30, 12925-12930, 2010.08.
55. H. Ago, I. Tanaka, M. Tsuji, K. Ikeda, Patterned growth of graphene over epitaxial catalyst, Small, 6, 11, 1226-1233, 2010.06.
56. H. Ago, K. Imamoto, T. Nishi, M. Tsuji, T. Ikuta, and K. Takahashi, Direct growth of bent carbon nanotubes on surface engineered sapphire, J. Phys. Chem. C, 113(30), 13121-13124., 2009.07.
57. N. Yoshihara, H. Ago, M. Tsuji, T. Ikuta, and K. Takahashi, Horizontally aligned growth of single-walled carbon nanotubes on surface modified silicon wafer, J. Phys. Chem. C, 113(19), 8030-8034, 2009.05.
58. C. M. Orofeo, H. Ago,* N. Yoshihara, and M. Tsuji, Top-down approach to align single-walled carbon nanotubes on silicon substrate, Appl. Phys. Lett., 94(5), 053113-1-3, 2009.02.
59. N. Ishigami, H. Ago, T. Nishi, K. Ikeda, M. Tsuji, T. Ikuta, and K. Takahashi , Unidirectional growth of single-walled carbon nanotubes, J. Am. Chem. Soc. , 130(51), 17264-17265, 2008.12.
60. N. Ishigami, H. Ago, K. Imamoto, M. Tsuji, K. Iakoubovskii, and N. Minami, Crystal plane dependent growth of aligned single-walled carbon nanotubes on sapphire, J. Am. Chem. Soc., 130(30), 9918-9924 (2008). , 2008.07.
61. H. Ago, N. Ishigami, N. Yoshihara, K. Imamoto, K. Ikeda, M. Tsuji, T. Ikuta, and K. Takahashi, Visualization of horizontally-aligned single-walled carbon nanotube growth with 13C/12C isotopes, J. Phys. Chem. C, J. Phys. Chem. C (Letter), 112(6), 1735-1738 (2008.2). selected as cover, 2008.02.
62. N. Ishigami, H. Ago, Y. Motoyama, M. Takasaki, M. Shinagawa, K. Takahashi, K. Takahashi, and M. Tsuji, Microreactor utilizing a vertically-aligned carbon nanotube array grown inside the channels, Chem. Commun., 1626-1628, 2007.03.
63. H. Ago, K. Imamoto, N. Ishigami, R. Ohdo, K. Ikeda, and M. Tsuji, Competition and cooperation between lattice-oriented growth and step-templated growth on aligned carbon nanotubes on sapphire, Appl. Phys. Lett., 90(12), 123112-1-3, 2007.03.
64. H. Ago, N. Uehara, N. Yoshihara, M. Tsuji, M. Yumura, N. Tomonaga, and T. Setoguchi, Gas analysis of CVD process for high yield growth of carbon nanotubes over metal-supported catalysts, Carbon, 44(14), 2912-2918 , 2006.11.
65. H. Ago, K. Nakamua, K. Ikeda, N. Uehara, N. Ishigami, and M. Tsuji, Aligned growth of isolated single-walled carbon nanotubes programmed by atomic arrangement of substrate surface, Chem. Phys. Lett., 10.1016/j.cplett.2005.04.054, 408, 4-6, 433-438, 408(4-6), 433-438 (2005)., 2005.06.
66. H. Ago, S. Imamura, T. Okazaki, T. Saito, M. Yumura, and M. Tsuji, CVD growth of single-walled carbon nanotubes with a narrow diameter distribution and their optical properties", J. Phys. Chem. B, 10.1021/jp050307q, 109, 20, 10035-10041, 109(20), 10035-10041 (2005)., 2005.05.
67. H. Ago, S. Ohshima, K. Tsukagoshi, M. Tsuji, and M. Yumura, Formation mechanism of carbon nanotubes in the gas-phase synthesis from colloidal solutions of nanoparticles, Curr. Appl. Phys., 10.1016/j.cap.2004.06.004, 5, 2, 128-132, 5(2), 128-132 (2005)., 2005.02.
68. H. Ago, K. Nakamura, N. Uehara, and M. Tsuji, Roles of meal-support interaction in growth of single- and double-walled carbon nanotubes studied with diameter-controlled iron particles supported on MgO, J. Phys. Chem. B, 108 (49), 18908-18915 (2004)., 2004.12.
69. H. Ago, K. Nakamura, S. Imamura, and M. Tsuji, Growth of double-wall carbon nanotube with diameter-controlled iron oxide nanoparticles supported on MgO, Chemical Physics Letters, 10.1016/j.cplett.2004.04.110, 391, 4-6, 308-313, 391(4-6), 308-313 (2004)., 2004.06.
70. Y. Zhang, H. Ago, J. Liu, M. Yumura, K. Uchida S. Ohshima, S. Iijima, J. Zhu, X. Zhang, The synthesis of In, In2O3 nanowires and In2O3 nanoparticles with shape-controlled, Journal of Crystal Growth, 264, 363-368 (2004)., 2004.04.
71. H. Ago, J. Qi, K. Tsukagoshi, K. Murata, S. Ohshima, Y. Aoyagi, and M. Yumura, Catalytic growth of carbon nanotubes and their patterning based on ink-jet and lithographic techniques, Journal of Electroanalytical Chemistry, 559, 25-30 (2003)., 2003.11.
72. H. Ago, K. Murata, M. Yumura, J. Yotani, and S. Uemura, Ink-Jet Printing of Nanoparticle Catalyst for Site-Selective Carbon Nanotube Growth, Applied Physics Letters, 82(5), 811-813 (2003)., 2003.02.
73. T. Kimura, H. Ago, M. Tobita, S. Ohshima, M. Kyotani, and M. Yumura, Polymer Composites of Carbon Nanotubes Aligned by a Magnetic Field, Advanced Materials, 14(19), 1380-1383 (2002)., 2002.10.
74. H. Ago, S. Ohshima, K. Uchida, T. Komatsu, and M. Yumura, Carbon nanotube synthesis using colloidal solution of metal nanoparticles, Physica B, 323(1-4), 306-307 (2002)., 2002.10.
75. H. Ago, S. Ohshima, K. Uchida, and M. Yumura, Gas-phase synthesis of single-wall carbon nanotubes from colloidal solution of metal nanoparticles, The Journal of Physical Chemistry B, 105(43), 10453-10456 (2001)., 2001.11.
76. H. Ago, T. Komatsu, S. Ohshima, Y. Kuriki, and M. Yumura, Dispersion of metal nanoparticles for aligned multiwall carbon nanotube arrays, Applied Physics Letters, 77(1), 79-81 (2000)., 2000.07.
77. H. Ago, M. S. P. Shaffer, D.S. Ginger, A. H. Windle, and R. H. Friend, Electronic interaction bewteen photo-excited poly(p-phenylene vinylene) and carbon nanotubes, Physical Review B, 61(3), 2286-2290 (2000)., 2000.01.
78. H. Ago, K. Petritsch, M. S. P. Shaffer, A. H. Windle, and R. H. Friend, Composites of carbon nanotubes and conjugated polymers for photovoltaic devices, Advanced Materials, 11(15), 1281-1285 (1999)., 1999.10.
79. K. Tsukagoshi, B. W. Alphenaar, and H. Ago, Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube, Nature, 401, 572-574 (1999)., 1999.10.
80. H. Ago, Th. Kugler, F. Cacialli, W. R. Salaneck, M. S. P. Shaffer, A. H. Windle, and R. H. Friend, Work functions and surface functional groups of multiwall carbon nanotubes, The Journal of Physical Chemistry B, 103(38), 8116-8121 (1999)., 1999.09.
81. H. Ago, M. Kato, K. Yahara, K. Yoshizawa, K. Tanaka, and T. Yamabe, Ab initio study on interaction and stability of lithium-doped amorphous carbons, Journal of the Electrochemical Society, 146(4), 1262-1269 (1999)., 1999.04.
82. H. Ago, K. Tanaka, T. Yamabe, T. Miyoshi, K. Takegoshi, T. Terao, S. Yata, Y. Hato, and N. Ando, Structural analysis of polyacenic semiconductor (PAS) materials with 129Xe NMR measurements, Carbon, 35, 1781-1787 (1997)., 1997.12.
83. H. Ago, K. Tanaka, T. Yamabe, K. Takegoshi, T. Terao, S. Yata, Y. Hato, and N. Ando, 7Li NMR study of Li-doped polyacenic semiconductor (PAS) materials, Synthetic Metals, 89, 141 (1997)., 1997.08.
84. H. Ago, K. Nagata, K. Yoshizawa, K. Tanaka, and T. Yamabe, Theoretical study of Li-doped polycyclic aromatic hydrocarbons, Bulletin of the Chemical Society of Japan, 70, 1717-1726 (1997)., 1997.07.
85. H. Ago, T. Kuga, T. Yamabe, K. Tanaka, A. Kunai, and M. Ishikawa, Electronic properties of p-type doped copolymers consisting of oligothienylene and disilanylene units, Chemistry of Materials, 9, 1159-1165 (1997)., 1997.05.
86. H. Ago, T. Kuga, T. Yamabe, K. Tanaka, S. Yata, Y. Hato, and N. Ando, ESR study of alkali-doped polyacenic semiconductor (PAS) materials prepared by
thermal decomposition of azides, Carbon, 35, 651-656 (1997)., 1997.12.
Presentations
 Show All Presentations >>
1. Hiroki Ago, Large-scale growth and integration of high-quality 2D materials for 2.5D materials science, JAIST International symposium of Nano-Materials for Novel Devices, 2024.01.
2. Hiroki Ago, "Large area hexagonal boron nitride sheet for 2D electronic devices, International Display Workshops (IDW'23), 2023.12.
3. Hiroki Ago, Large-area synthesis and transfer of multilayer hexagonal boron nitride for high-performance graphene device arrays, 13th A3 Symposium on Emerging Materials: Nanomaterials for Electronics, Energy, and Environment, 2023.10.
4. Hiroki Ago, "Wafer-scale synthesis and applications of multilayer hexagonal boron nitride, 2023 International Workshop on Dielectric Thin Films for Fugure Electron Devices (IWDTF2023), 2023.10.
5. Hiroki Ago, From 2D materials to 2.5D materials science, The 7th Symposium on Challenges for Carbon-based Nanoporous Materials (7CBNM), 2023.10.
6. Hiroki Ago, Controlled synthesis and electronic applications of 2.5D materials, 33rd International Conference on Diamond and Carbon Materials (ICDCM2023), 2023.09.
7. Hiroki Ago, Synthesis and Electronic Applications of Wafer-Scale 2.5D Materials, SSDM2023 (International Conference on Solid State Devices and Materials), 2023.09.
8. Hiroki Ago, Controlled CVD growth of multilayer hBN for 2.5D applications, 2D Transition Metal Dichalcogenides, 2023.06.
9. Hiroki Ago, Controlled CVD gowth of multilayer hBN for 2.5D applications, Inaugural Workshop on Boron Nitride, 2023.05.
10. Hiroki Ago, Science of 2.5-Dimensional Materials: Controlled Growth, Integration, and Applications of 2D Materials, PIREキックオフミーティング（Japan US Networks for Clean energy Technologies Involving Oriented Nanotubes）, 2023.05.
11. Hiroki Ago, From 2D materials to 2.5D materials science, RPGR2022 (Recent Progress in Graphene and Two-Dimensional Materials Research Conference), 2022.11.
12. Hiroki Ago, Twist angle-dependent molecular intercalation and carrier transport in bilayer graphene, 12th A3 Symposium on Emerging Materials, 2022.11.
13. Hiroki Ago, Science of 2.5-Dimensional Materials: Controlled Growth, Integration, and Applications of 2D Materials, IUMRS-ICAM2022, 2022.08.
14. Hiroki Ago, Science of 2.5 Dimensional Materials, Users' Meeting of Brookhaven National Laboratory "2D Materials and Beyond (Workshop 7), 2022.05.
15. H. Ago, 2.5-Dimensional Materials Science: Controlled Growth, Integration, and Applications of Graphene and h-BN, ISPlasma2022, 2022.03.
16. H. Ago, Bilayer graphene: CVD growth, machine learning-based analysis, and intercalation, The 9th International Workshop on 2D Materials, 2022.02.
17. H. Ago, Bilayer graphene: CVD growth, machine learning-based analysis, and intercalation, 11th Asian Nanomaterials symposium (A3), 2021.12.
18. H. Ago, Highly Controlled CVD Synthesis of Monolayer and Multilayer h-BN for 2D Materials Applications, Graphene2020, 2020.10.
19. H. Ago, Synthesis of high-quality 2D materials for electronic applications, 2020 VLSI-TSA (VLSI: Technology, Systems and Applications), 2021.08.
20. H. Ago, Syntheses and growth mechanisms of 2D materials, A3 Foresight Program, 2020.07.
21. H. Ago, Controlled synthesis and processing of 2D materials for future applications, 1 & 2DM Conference and Exhibition 2020, 2020.01.
22. H. Ago, Controlled synthesis of 2D materials and their heterostructures for device applications, The 3rd Workshop on Functional Materials Science, 2019.12.
23. H. Ago, Controlled CVD growth of high-quality 2D layered materials for electronic and photonic applications, Materials Research Meeting 2019, 2019.12.
24. H. Ago, Controlled CVD growth of high-quality 2D materials and their heterostructures for electronic applications, 10th A3 Symposium on Emerging Materials: Nanomaterials for Electronics, Energy and Environment, 2019.10.
25. H. Ago, Controlled CVD growth of high-quality 2D materials and their heterostructures for electronic applications, RPGR2019 (Recent Progress in Graphene and 2D Materials Research), 2019.10.
26. H. Ago, Controlled CVD Growth of High-Quality 2D Materials and Their Heterostructures for Device Applications, SSDM2019 (Solid State Devices and Materials 2019), 2019.09.
27. H. Ago, Controlled synthesis of high-quality 2D materials for device applications, 2019 Symposia on VLSI Technology and Circuits, 2019.06.
28. H. Ago, Controlled CVD synthesis of high-quality 2D materials for electronic and photonic applications, 3rd EU-JP Flagship Workshop on Graphene & 2DMs, 2018.11.
29. H. Ago, Controlled CVD synthesis of high-quality 2D materials for electronic and photonic applications, First International Workshop on 2D Materials, 2018.11.
30. H. Ago, CVD Growth of large-area, uniform multilayer h-BN as a platform of 2D material applications, 9th A3 Symposium on Emerging Materials: Nanomaterials for Electronics, Energy and Environment, 2018.10.
31. H. Ago, Controlled synthesis of high-quality 2D materials for electronic and photonic applications, IUMRS-IECM 2018 (International Conference on Electronic Materials 2018), 2018.08.
32. H. Ago, Controlled growth of high-quality graphene and various 2D materials for enhancing their applications, CIMTEC 2018 (International Conference on Modern Materials and Technologies), 2018.06.
33. H. Ago, Syntheses and applications of bilayer and multilayer graphene, 8th A3 Symposium on Emerging Materials, 2017.10.
34. H. Ago, Exploring the Growth of High-Quality Graphene, Related 2D Materials, and Their Heterostructures for Electronic Applications, 2017 NEA Symposium of Emerging Materials Innovation（第19回北東アジアシンポジウム）, 2017.10.
35. H. Ago, High-quality graphene and related 2D materials for future IoT society, IUMRS-ICAM 2017 (The 15th International Conference on Advanced Materials), 2017.08.
36. H. Ago, Crystal growth and device applications of two-dimensional layered materials, AM-FPD'17 (24th Intenational Workshop on Active-Matrix Flatpanel Displays and Devices), 2017.07.
37. H. Ago, Syntheses of high-quality graphene and related 2D materials for enhancing their applications, Graphene EU Flagship-Japan Second Workshop, 2017.05.
38. H. Ago, Exploring the growth of high-quality graphene and 2D heterostructures for electronic applications, The 6th International Symposium on Micro and Nano Technology, 2017.03.
39. H. Ago, Synthesis and application of graphene and 2D heterostructures, ISPlasma2017/IC-PLANTS2017, 2017.03.
40. H. Ago, Epitaxial Growth of Graphene and Related 2D Materials for Electronic Applications, The 6th NIMS-UR1-CNRS-SG Workshop, 2016.10.
41. H. Ago, Synthesis and processing of graphene and related 2D materials for electronic applications, 4th Malaysia 2D Materials and Carbon Nanotube Workshop (2DMC2016), 2016.10.
42. H. Ago, Vertical and In-Plane Heterostructures of Graphene and MoS2, IUMRS-IECM2016 (IUMRS International Conference on Electronic Materials), 2016.03.
43. H. Ago, ”Exploring the growth of graphene and related 2D materials for electronic applications, Pacifichem2015 (Carbon Nanotubes: Preparation, Characterization and Applications), 2015.12.
44. H. Ago, Epitaxial CVD Growth of High-Quality Graphene and Recent Development of 2D Heterostructures, IEDM 2015 (International Electron Devices Meeting 2015), 2015.12.
45. H. Ago, H. Endo, Y. Shiratsuchi, R. M. Yunus, S. Fukamachi, P. Solís Fernández, K. Kawahara, K. Yamamoto, M. Tsuji, H. Hibino, Vertical and in-plane heterostructures of graphene and MoS2, The 6th A3 Symposium on Emerging Materials, 2015.11.
46. H. Ago, Exploring the growth of graphene and related 2D materials for electronic applications, 1st EU-Japan Workshop on Graphene and Related 2D Material, 2015.10.
47. H. Ago, Exploring the Growth of Graphene and Related 2D Materials for Electronic Applications, 11th International Conference of Pacific Rim Ceramic Societies (PacRim-11), 2015.09.
48. H. Ago, Synthesis, Characterization, and Applications of Single- and Double-Layer Graphene Grown on Epitaxial Metal Films, 227th ECS Meeting, 2015.03.
49. 吾郷 浩樹, Exploring the growth of graphene and related 2D materials for electronic applications, 北海道大学電子科学研究所 シンポジウム「響」, 2014.12.
50. Yui Ogawa, Kenji Kawahara, Masahiro Miyashita, Masaharu Tsuji, Katsuyoshi Komatsu, Kazuhito Tsukagoshi, Hiroki Ago, Transport properties and defects at the intersection of CVD graphene domains, SSDM2013 (International Conference on Solid State Devices and Materials), 2013.09.
51. Hiroki Ago, Graphene and nanoribbons: epitaxial CVD growth, processing, and applications, 2013 JSAP-MRS Joint Symposia, 2013.09.
52. Hiroki Ago, Towards single-crystalline graphene by catalytic CVD, IUMRS-ICEM 2012 , 2012.09.
53. Hiroki Ago, Epitaxial CVD growth of graphene, KJF International Conference on Organic Materials for Electronics and Photonics 2012, 2012.09.
54. Hiroki Ago, Single- and Double-Layer Graphene on Heteroepitaxial Metal Films, icsfs 16 (International Conference on Solid Films and Surfaces), 2012.07.
55. Surface atomic arrangement-programmed growth of horizontally-aligned SWNTs on sapphire.
56. Aligned growth of single-walled carbon nanotubes programmed by single crystal surface.
57. Aligned growth of single-walled carbon annotubes and their characterization.
Membership in Academic Society
  • The Fullerenes, Nanotubes, and Graphene Research Society
  • The Japan Society of Applied Physics
  • Chemical Society of Japan
  • The Carbon Society of Japan
Awards
  • Epitaxial Growth and Electronic Properties of Large Hexagonal Graphene Domains on Cu(111) Thin Film
  • Investigation of mechanical strain of graphene by Raman spectroscopy
  • Iijima award
  • Tsukuba prize (industrial part)
Educational
Educational Activities
Graduate school:
"Basics of solid state chemistry" and "Advanced functional materials" for graduate students in the Interdisciplinary Graduate School of Engineering Sciences.

Undergraduate school:
"Basic theory of chemical bonds" for KIKAN education (FY2024-present)
"Recent advances of physics" for KIKAN education (FY2019-2020)
"Molecular Sciences" for undergraduate students belonging to all the departments (FY 2013-2015).
Other Educational Activities
  • 2019.04.
  • 2019.04.
  • 2018.04.
  • 2012.11.
  • 2008.08.


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