九州大学 研究者情報
論文一覧
吾郷 浩樹(あごう ひろき) データ更新日:2019.07.30

教授 /  グローバルイノベーションセンター アドバンストプロジェクト部門 総合理工学府 物質理工学専攻 先進ナノマテリアル科学研究室


原著論文
1. 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.
2. 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, [URL], 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..
3. Masaharu Tsuji, Kanako Matsuda, Mayu Tanaka, Satsuki Kuboyama, Keiko Uto, Nozomi Wada, Hirofumi Kawazumi, Takeshi Tsuji, Hiroki Ago, Jun Ichiro Hayashi, Enhanced Photocatalytic Degradation of Methyl Orange by Au/TiO2 Nanoparticles under Neutral and Acidic Solutions, ChemistrySelect, 10.1002/slct.201702664, 3, 5, 1432-1438, 2018.02, [URL], A comparative study was carried out on the degradation of methyl orange (MO) by TiO2 and Au/TiO2 photocatalysts in neutral and acidic solutions. Au/TiO2 photocatalysts with an Au : Ti atomic ratio of 1.5±0.1% : 98.5±0.1% were prepared by using a microwave-polyol method in the presence of P25 TiO2. Initial degradation rates of MO by TiO2 and Au/TiO2 were 0.13 and 0.22 min−1 at pH 7, whereas they increased to 0.96 and 3.06 min−1 at pH 2, respectively. These results indicate that the MO degradation rates are enhanced by loading Au nanoparticles on TiO2 in neutral and acidic solutions by factors of 1.7 and 3.2, respectively. Mass spectroscopic studies lead us to conclude that major reaction products are formed by demethylation and OH addition of benzenoid form of MO in neutral solutions, whereas they are produced through ring opening and carboxylation of quinonoid form of MO after scission of a center N-NH bond in acidic solutions. The relative importance of electron trapping and surface plasmon resonance (SPR) effects of Au nanoparticles is discussed for the enhancement of photocatalytic activity of Au/TiO2..
4. 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, [URL], 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..
5. 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, [URL], 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 ms) response time. The work of the heterostacked structure combining WS2, graphene, and the very thin polymer film will find applications in various flexible electronics, such as wearable high-performance optoelectronics devices..
6. 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, [URL], 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..
7. 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, [URL], 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..
8. Dong Ding, Pablo Solís-Fernández, Rozan Mohamad Yunus, Hiroki Hibino, Hiroki Ago, Behavior and role of superficial oxygen in Cu for the growth of large single-crystalline graphene, Applied Surface Science, 10.1016/j.apsusc.2017.02.250, 408, 142-149, 2017.06, [URL], Decreasing the nucleation density of graphene grown on copper (Cu) foil by chemical vapor deposition (CVD) is essential for the synthesis of large-area single-crystalline graphene. Here, the behavior of the copper oxide layer and its impact on the graphene growth have been investigated. We found that a small amount of oxygen dissolves into the Cu when the oxide layer decomposes during the heating up in a non-reducing Ar environment. The remaining oxygen in the Cu foil can play an important role in decreasing the graphene nucleation density. The dissolved oxygen can withstand at high temperatures even in reducing H2 environments without completely losing its effectiveness for maintaining a low graphene nucleation density. However, heating up in a H2 environment significantly reduces the copper oxide layer during the very first moments of the process at low temperatures, preventing the oxygen to dissolve into the Cu and significantly increasing the nucleation density. These findings will help to improve the graphene growth on Cu catalyst by increasing the grain size while decreasing the grain density..
9. 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, [URL], 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..
10. 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, [URL], 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..
11. Naohiro Fujita, Daisuke Matsumoto, Yuki Sakurai, Kenji Kawahara, Hiroki Ago, Taishi Takenobu, Kazuhiro Marumoto, Direct observation of electrically induced Pauli paramagnetism in single-layer graphene using ESR spectroscopy, Scientific Reports, 10.1038/srep34966, 6, 2016.10, [URL], Graphene has been actively investigated as an electronic material owing to many excellent physical properties, such as high charge mobility and quantum Hall effect, due to the characteristics of a linear band structure and an ideal two-dimensional electron system. However, the correlations between the transport characteristics and the spin states of charge carriers or atomic vacancies in graphene have not yet been fully elucidated. Here, we show the spin states of single-layer graphene to clarify the correlations using electron spin resonance (ESR) spectroscopy as a function of accumulated charge density using transistor structures. Two different electrically induced ESR signals were observed. One is originated from a Fermi-degenerate two-dimensional electron system, demonstrating the first observation of electrically induced Pauli paramagnetism from a microscopic viewpoint, showing a clear contrast to no ESR observation of Pauli paramagnetism in carbon nanotubes (CNTs) due to a one-dimensional electron system. The other is originated from the electrically induced ambipolar spin vanishments due to atomic vacancies in graphene, showing a universal phenomenon for carbon materials including CNTs. The degenerate electron system with the ambipolar spin vanishments would contribute to high charge mobility due to the decrease in spin scatterings in graphene..
12. Haidong Wang, Kosaku Kurata, Takanobu Fukunaga, Hiroki Ago, Hiroshi Takamatsu, Xing Zhang, Tatsuya Ikuta, Koji Takahashi, Takashi Nishiyama, Yasuyuki Takata, A general method of fabricating free-standing, monolayer graphene electronic device and its property characterization, Sensors and Actuators, A: Physical, 10.1016/j.sna.2016.05.002, 247, 24-29, 2016.08, [URL], We demonstrate a general process for fabricating graphene nanoelectronic devices that have next several features: free-standing, micrometer-sized monolayer graphene with high quality, arbitrarily-shaped metallic electrodes or sensors. In contrast to the normal routes, a gas etching process is used to create a deep trench in silicon for suspending the whole graphene device in a much larger area. User-designed electrodes or sensors are fabricated on the suspended graphene at the same time for realizing multiple functions. In this work, a suspended gold nanofilm sensor is designed to measure the intrinsic electrical and thermal properties of graphene on site. The sensor serves as both electrode and precise resistance thermometer at the same time. By simply changing the metallic electrode shape and electrical circuit, the free-standing graphene can be made into different devices, such as single-molecule detector or nano-resonator. In order to test the robustness of graphene device, a high electrical current is applied to heat the graphene in vacuum until it breaks. The breakdown current density is measured to be 1.86 mA/μm. More importantly, this method is not only limited to graphene, but also can be applied to any other two-dimensional materials..
13. 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, [URL], 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..
14. Haidong Wang, Kosaku Kurata, Takanobu Fukunaga, Hiroki Ago, Hiroshi Takamatsu, Xing Zhang, Tatsuya Ikuta, Koji Takahashi, Takashi Nishiyama, Yasuyuki Takata, Simultaneous measurement of electrical and thermal conductivities of suspended monolayer graphene, Journal of Applied Physics, 10.1063/1.4954677, 119, 24, 2016.06, [URL], We measured both in-plane electrical and thermal properties of the same suspended monolayer graphene using a novel T-type sensor method. At room temperature, the values are about 240 000 Ω-1 m-1 and 2100 W m-1 K-1 for the electrical and thermal conductivities, respectively. Based on the Wiedemann-Franz law, the electrons have negligible contribution to the thermal conductivity of graphene, while the in-plane LA and TA modes phonons are the dominant heat carriers. In monolayer graphene, the absence of layer-layer and layer-substrate interactions enhances the contribution of long wave-length phonons to the heat transport and increases the thermal conductivity accordingly. The reported method and experimental data of suspended monolayer graphene are useful for understanding the basic physics and designing the future graphene electronic devices..
15. Takeshi Koyama, Kenta Mizutani, Hiroki Ago, Hideo Kishida, Two-Step Excitation Triggered by One-Photon Absorption on Linear Dispersion in Monolayer Graphene, Journal of Physical Chemistry C, 10.1021/acs.jpcc.6b01490, 120, 20, 11225-11229, 2016.05, [URL], We report the decrease in absorption caused by a near-infrared laser pulse in the visible region in monolayer graphene. This absorption decrease shows the existence of a two-step excitation process of carriers, in which one-photon absorption and Auger recombination sequentially occur. This process results from the linear dispersion nature of monolayer graphene. In addition, the monolayer graphene shows the ultrafast decay of carrier population. The observed properties are of importance for ultrafast optical switching utilizing the optical nonlinearity induced by carrier excitation..
16. Haidong Wang, Kosaku Kurata, Takanobu Fukunaga, Hiroshi Takamatsu, Xing Zhang, Tatsuya Ikuta, Koji Takahashi, Takashi Nishiyama, Hiroki Ago, Yasuyuki Takata, A simple method for fabricating free-standing large area fluorinated single-layer graphene with size-tunable nanopores, Carbon, 10.1016/j.carbon.2015.12.070, 99, 564-570, 2016.04, [URL], As a solid-state membrane with only one-atom thickness, nano-porous graphene has attracted intense attention in many critical applications. Here, the key challenge is to suspend a single-layer graphene (SLG) and drill nanopores with precise dimensions. Here, we report a simple and reliable route for making suspended fluorinated SLG with size-tunable nanopores. Our method consists of two steps: 1. a free-standing SLG ribbon was created between two gold pads after deep dry etching of silicon substrate by xenon difluoride. The SLG was fluorinated by 5-13%. Superior to the normal wet etching method, the dry etching process is much simpler and results in less hole-defect and edge deformation. A large area fluorinated SLG can be suspended due to the sufficient etch depth. 2. a focused ion beam was introduced to drill nanopores in graphene with an initial diameter around 20 nm. Followed by an electron beam induced carbon deposition, the diameter of nanopore was gradually decreased to sub-10 nm. By changing the deposition time, the size of nanopore can be precisely controlled. High-cost transmission electron microscope is no longer needed. Our method provides a simple and effective way for preparing free-standing fluorinated SLG ribbon suitable for single-molecule detection..
17. S. Dushenko, Hiroki Ago, K. Kawahara, T. Tsuda, S. Kuwabata, T. Takenobu, T. Shinjo, Y. Ando, M. Shiraishi, Gate-Tunable Spin-Charge Conversion and the Role of Spin-Orbit Interaction in Graphene, Physical Review Letters, 10.1103/PhysRevLett.116.166102, 116, 16, 2016.04, [URL], The small spin-orbit interaction of carbon atoms in graphene promises a long spin diffusion length and the potential to create a spin field-effect transistor. However, for this reason, graphene was largely overlooked as a possible spin-charge conversion material. We report electric gate tuning of the spin-charge conversion voltage signal in single-layer graphene. Using spin pumping from an yttrium iron garnet ferrimagnetic insulator and ionic liquid top gate, we determined that the inverse spin Hall effect is the dominant spin-charge conversion mechanism in single-layer graphene. From the gate dependence of the electromotive force we showed the dominance of the intrinsic over Rashba spin-orbit interaction, a long-standing question in graphene research..
18. 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, [URL], 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..
19. Haidong Wang, Kosaku Kurata, Takanobu Fukunaga, Hiroshi Takamatsu, Xing Zhang, Tatsuya Ikuta, Koji Takahashi, Takashi Nishiyama, Hiroki Ago, Yasuyuki Takata, In-situ measurement of the heat transport in defect-engineered free-standing single-layer graphene, Scientific Reports, 10.1038/srep21823, 6, 2016.02, [URL], Utilizing nanomachining technologies, it is possible to manipulate the heat transport in graphene by introducing different defects. However, due to the difficulty in suspending large-area single-layer graphene (SLG) and limited temperature sensitivity of the present probing methods, the correlation between the defects and thermal conductivity of SLG is still unclear. In this work, we developed a new method for fabricating micro-sized suspended SLG. Subsequently, a focused ion beam (FIB) was used to create nanohole defects in SLG and tune the heat transport. The thermal conductivity of the same SLG before and after FIB radiation was measured using a novel T-type sensor method on site in a dual-beam system. The nanohole defects decreased the thermal conductivity by about 42%. It was found that the smaller width and edge scrolling also had significant restriction on the thermal conductivity of SLG. Based on the calculation results through a lattice dynamics theory, the increase of edge roughness and stronger scattering on long-wavelength acoustic phonons are the main reasons for the reduction in thermal conductivity. This work provides reliable data for understanding the heat transport in a defective SLG membrane, which could help on the future design of graphene-based electrothermal devices..
20. 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, [URL], 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..
21. 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.
22. 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.
23. 服部 真史, Daisuke Shimamoto, Hiroki Ago, Masaharu Tsuji, AgPd@Pd/TiO2 nanocatalyst synthesis by microwave heating in aqueous solution for efficient hydrogen production from formic acid, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c5ta01434d, 3, 20, 10666-10670 , 2015.04.
24. 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.
25. Qin-Yi Li, Koji Takahashi, Hiroki Ago, Zhang, Xing, Ikuta, Tatsuya, Takashi Nishiyama, Kenji Kawahara, Temperature dependent thermal conductivity of a suspended submicron graphene ribbon, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4907699, 117, 6, 065102, 2015.02.
26. SOLIS FERNANDEZ PABLO, MARK ALEXANDER BISSETT, Masaharu Tsuji, Hiroki Ago, Tunable doping of graphene nanoribbon arrays by chemical functionalization, NANOSCALE, 10.1039/c4nr07007k, 7, 8, 3572-3580 , 2015.01.
27. MARK ALEXANDER BISSETT, Yuichiro Takesaki, Masaharu Tsuji, Hiroki Ago, Increased chemical reactivity achieved by asymmetrical 'Janus' functionalisation of graphene, RSC Advances, 4, 52215-52219, 2014.10.
28. Kawasaki, Tetsuya, Sugawara, Kenta, Dobroiu, Adrian, Eto, Takanori, Kurita, Yuki, Kojima, Kazuki, Yabe, Yuhei, Sugiyama, Hiroki, Watanabe, Takayuki, Suemitsu, Tetsuya, Ryzhii, Victor, Iwatsuki, Katsumi, Fukada, Youichi, Kani, Jun-ichi, Terada, Jun, Yoshimoto, Naoto, Kenji Kawahara, Hiroki Ago, Otsuji, Taiichi, Graphene-channel FETs for photonic frequency double-mixing conversion over the sub-THz band, SOLID-STATE ELECTRONICS, 10.1016/j.sse.2014.07.009, 103, 216-221 , 2015.01.
29. R. Ohshima, A. Sakai, Y. Ando, T. Shinjo, K .Kawahara, Hiroki Ago, S. Shiraishi, Observation of spin-charge conversion in CVD-grown single-layer graphene, Applied Physics Letters, 105, 162410, 2014.10.
30. Hiroki Ago, Yasumichi Kayo, SOLIS FERNANDEZ PABLO, Kazuma Yoshida, Masaharu Tsuji, Synthesis of high-density arrays of graphene nanoribbons by anisotropic metal-assisted etching, CARBON, 10.1016/j.carbon.2014.07.010, 78, 339-346, 2014.11.
31. 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.
32. 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.
33. Hu BaoShan, ZiDong Wei, Hiroki Ago, Jin Yan, Xia MeiRong, Luo ZhengTang, Pan QingJiang, Liu YunLing, Effects of substrate and transfer on CVD-grown graphene over sapphire-induced Cu films, Science China Chemistry, 10.1007/s11426-014-5073-3, 57, 6, 895-901, 2014.06.
34. MARK ALEXANDER BISSETT, Masaharu Tsuji, Hiroki Ago, Strain Engineering the Properties of Graphene and Other Two-Dimensional Crystals, Physical Chemistry Chemical Physics, 16, 23, 11124-11138 , 2014.06.
35. 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.
36. 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.
37. 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.
38. Yui Ogawa, Tianchao Niu, Swee Liang Wong, Masaharu Tsuji, Andrew Thye Shen Wee, Wei Chen, Hiroki Ago, Self-assembly of polar phthalocyanine molecules on graphene grown by chemical vapor deposition, Journal of Physical Chemistry C, 117, 42, 21849-21855, 2013.10.
39. 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.
40. 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.
41. Xiaoyang Hu, Yingjiu Zhang, Hiroki Ago, Huihua Zhou, Xiao Li, Lili Fan, Bin Cai, Xinjian Li, Minlin Zhong, Kunlin Wang, Dehai Wu, Hongwei Zhu, Ultra-fast synthesis of graphene by melt spinning, Carbon, 61, 299-304, 2013.09.
42. GE WANYIN, kenji Kawahara, Masaharu Tsuji, Hiroki Ago, Large-scale synthesis of NbS2 nanosheets with controlled orientation on graphene by ambient pressure CVD, Nanoscale, 5, 13, 5773-5778, 2013.07.
43. Z. Tang, E. Shikoh, Hiroki Ago, K. Kawahara, Y. Ando, T. Shinjo, M. Shiraishi, Dynamically-generated pure spin current in single-layer graphene, Phys. Rev. B (Rapid Communication), 87, 14, 140401-1-5, 2013.04.
44. T. Koyama, Y. Ito, K. Yoshida, Masaharu Tsuji, Hiroki Ago, H. Kishida, A. Nakamura, Near-infrared photoluminescence in the femtosecond time region in monolayer graphene, ACS Nano, 7, 3, 2335-2443, 2013.03.
45. MARK ALEXANDER BISSETT, Masaharu Tsuji, Hiroki Ago, Mechanical strain of chemically functionalized chemical vapor deposition grown graphene, J. Phys. Chem. C, 117, 6, 3152-3159, 2013.02.
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. C. M. Orofeo, H. Hibino, K. Kawahara, Y. Ogawa, M. Tsuji, K. Ikeda, S. Mizuno, H. Ago, Influence of Cu metal on the domain structure and carrier mobility in single-layer grap, Carbon, 50, 6, 2189-2196, 2012.06.
50. H. Ago, Y. Kayo, M. Tsuji, Growth of horizontally-aligned single-walled carbon nanotubes on sapphire surface by needle-scratching method, Jpn. J. Appl. Phys., 51, 4, 04DN02-1-4, 2012.04.
51. 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.
52. B. Hu, H. Ago, C. M. Orofeo, Y. Ogawa, M. Tsuji, On the nucleation of graphene in chemical vapor deposition, New J. Chem., 36, 1, 73-76, 2012.01.
53. 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.
54. 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.
55. 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.
56. H. Ago, Y. Nakamura, Y. Ogawa, M. Tsuji, Combinatorial catalyst approach for high-density growth of horizontally aligned single-walled carbon nanotubes on sapphire, Carbon, 49, 1, 176-186, 2011.01.
57. 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.
58. C. M. Orofeo, H. Ago, N. Yoshihara, M. Tsuji, Methods to horizontally align single-walled carbon nanotubes on amorphous substrate
, J. Novel Carbon Resourse Sci., 2, 36-40, 2010.09.
59. Y. Ogawa, H. Ago, M. Tsuji , Epitaxial growth of faceted Co nanoparticles on sapphire surfaces, Chem. Lett., 39, 9, 964-965, 2010.09.
60. 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.
61. C. M. Orofeo, H. Ago, T. Ikuta, K. Takahashi, M. Tsuji , Growth of horizontally aligned single-walled carbon nanotubes on anisotropically etched silicon substrate, Nanoscale, 2, 9, 1708-1714, 2010.09.
62. J. Onoda, S. Mizuno, H. Ago, STEM observation of tungsten tips sharpened by field-assisted oxygen etching
, Surf. Sci., 604, 13-14, 1094-1099, 2010.07.
63. H. Ago, I. Tanaka, M. Tsuji, K. Ikeda, Patterned growth of graphene over epitaxial catalyst, Small, 6, 11, 1226-1233, 2010.06.
64. H. Ago, C. M. Orofeo, N. Ishigami, N. Yoshihara, M. Tsuji, Recent development in technology for horizontally-aligned growth of single-walled carbon nanotubes, Sens. Mater., 21(7), 321-330, 2009.12.
65. H. Ago, R. Ohdo, M. Tsuji, T. Ikuta, and K. Takahashi, Effective patterning of metal nanoparticles on sapphire surface for aligned growth of single-walled carbon nanotubes, J. Nanosci. Nanotech., 10(6), 3867-3872., 2010.06.
66. B. Hu, H. Ago, N. Yoshihara, and M. Tsuji, Effects of water vapor on diameter distribution of SWNTs grown over Fe/MgO based catalysts, J. Phys. Chem. C, 114(9), 3850-3856., 2010.03.
67. A. Nakamura, N. Hikosaka, S. Imamura, Y. Takahashi, H. Ago, H. Kishida, Third-order nonlinear optical response in double-walled carbon nanotubes, J. Luminescence, 129(12), 1722-1725., 2009.12.
68. 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.
69. 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.
70. 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.
71. 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.
72. H. Ago, N. Ishigami, K. Imamoto, T. Suzuki, K. Ikeda, M. Tsuji, T. Ikuta, and K. Takahashi, Horizontally-aligned single-walled carbon nanotubes on sapphire, J. Nanosci. Nanotech., 8(11), 6165-6169, 2008.11.
73. H. Ago, I. Tanaka, M. Tsuji, K. Ikeda, and S. Mizuno , Hole-doping to aligned single-walled carbon nanotubes from sapphire induced by heat treatment, J. Phys. Chem. C, 112(47), 18350-18354, 2008.10.
74. 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.
75. H. Ago, N. Ishigami, K. Imamoto, T. Suzuki, K. Ikeda, M. Tsuji, T. Ikuta, and K. Takahashi, Horizontally-alinged single-walled carbon nanotubes on sapphire, J. Nanosci. Nanotech., J. Nanosci. Nanotech., in press (2008)., 2008.06.
76. N. Yoshihara, H. Ago, and M. Tsuji, Mechanism of carbon nanotube growth over gold-supported catalysts, Jpn. J. Appl. Phys., 47(4), 1944-1948 (2008).
, 2008.04.
77. 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.
78. N. Yoshihara, H. Ago, and M. Tsuji, Chemistry of water-assisted carbon nanotube growth over Fe-Mo/MgO catalyst, J. Phys. Chem. C, J. Phys. Chem. C, 111(31), 11577-11582 (2007)., 2007.08.
79. 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.
80. 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.
81. X. Zhang, H. Xie, M. Fujii, H. Ago, K. Takahashi, T. Ikuta, H. Abe, and T. Shimizu, Thermal and electrical properties of a suspended nanoscale thin film, Int. J. Heat Mass Transfer, Int. J. Thermophys., 28(1), 33-43 (2007.2)., 2007.02.
82. H. Ago, E. Uchimura, T. Saito, S. Ohshima, N. Ishigami, M. Tsuji, M. Yumura, and M. Miyake, Mechanical Immobilization of Hela Cells on aligned carbon nanotube array, Mater. Lett, 60(29-30), 3851-3854, 2006.12.
83. 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.
84. X. Zhang, H. Xie, M. Fujii, K. Takahashi, T. Ikuta, H. Ago, H. Abe, and T. Shimizu, Experimental study on thermal characteristics of suspended platinum nanofilm sensors, Int. J. Heat Mass Transfer, 49(21-22), 3879-3883, 2006.10.
85. A. Nakamura, T. Tomikawa, M. Watanabe, Y. Hamanaka, Y. Saito, and H. Ago, Nonlinear optical response and relaxation dynamics in double-walled carbon nanotubes, J. Luminescence, 119-120, 8-12, 2006.07.
86. H. Ago, N. Uehara, K.Ikeda, R. Ohdo, K. Nakamura, and M. Tsuji, Synthesis of horizontally-aligned single-walled carbon nanotubes with controllable density and polarized Raman spectroscopy, Chem. Phys. Lett., 421(4-6), 399-403, 2006.04.
87. T. Saito, W. C. Xu, S. Ohshima, H. Ago, M. Yumura, and S. Iijima, Supramoleclar catalysts for the gas-phase synthesis of single-walled carbon nanotubes, J. Phys. Chem. B, 110(12), 5849-5853, 2006.03.
88. M. Fujii, X. Zhang, H. Xie, H. Ago, K. Takahashi, T. Ikuta, H. Abe, and T. Shimizu, Measuring the thermal conductivity of a single carbon nanotub, Phys. Rev. Lett., 10.1103/PhysRevLett.95.065502, 95, 6, 95(6), 065502-1-4, 2005.08.
89. T. Saito, S. Ohshima, W. C. Xu, H. Ago, M. Yumura, and S. Iijima, Size-control of metal nanoparticle catalysts for the gas-phase synthesis of single-walled carbon nanotubes, J. Phys. Chem. B, 10.1021/jp044200z, 109, 21, 10647-10652, 109(21), 10647-10652 (2005)., 2005.07.
90. 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.
91. 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.
92. X. Zhang, H. Xie, M. Fujii, H. Ago, K. Takahashi, T. Ikuta, H. Abe, and T. Shimizu, Thermal and electrical conductivity of a suspended platinum nanofilm, Appl. Phys. Lett., 10.1063/1.1921350, 86, 17, 86(17), 171912-171912-3 (2005)., 2005.04.
93. 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.
94. 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.
95. 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.
96. 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.
97. Y. Zhang, H. Ago, M. Yumura, S. Ohshima, K. Uchida, T. Komatsu, and S. Iijima, Study of the growth of boron nanowires synthesized by laser ablation, Chemical Physics Letters, 385, 177-183 (2004)., 2004.01.
98. H. Ago, R. Azumi, S. Ohshima, H. Kataura, and M. Yumura, STM study of molecular adsorption on single-wall carbon nanotube surface, Chemical Physics Letters, 10.1016/j.cplett.2003.11.053, 383, 5-6, 469-474, 383, 469-474 (2004)., 2004.01.
99. 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.
100. K. Tsukagoshi, At. Suzuki, I. Yagi, E. Watanabe, Y. Aoyagi, H. Ago, S. Ohshima, and M. Yumura, High density current operation in nanographite fiber synthesized by chemical vapor deposition, Journal of Applied Physics, 2003.09.
101. 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.
102. Y. Zhang, H. Ago, M. Yumura, T. Komatsu, S. Ohshima, K. Uchida, and S. Iijima, Synthesis of crystalline boron nanowires by laser ablation, Chemical Communications, 2806 (2002)., 2002.12.
103. 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.
104. 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.
105. S. Ohshima, H. Ago, H. Inoue, and M. Yumura, Development of mass-production technology for multiwalled carbon nanotubes, New Diamond and Frontier Carbon Technology, 11(6), 437-448 (2001)., 2001.12.
106. 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.
107. B. W. Alphenaar, K. Tsukagoshi, and H. Ago, Spin electronics using carbon nanotubes, Physica E, 6(1-4), 848-851 (2000)., 2000.02.
108. 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.
109. 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.
110. 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.
111. 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.
112. 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.
113. 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.
114. H. Ago, Th. Kugler, F. Cacialli, K. Petritsch, R. H. Friend, W. R. Salaneck, Y. Ono, T. Yamabe, and K. Tanaka, Workfunction of purified and oxidized carbon nanotubes, Synthetic Metals, 103, 2494-2495 (1999)., 1999.11.
115. A. K. Bakhshi, Y. Yamaguchi, H. Ago, and T. Yamabe, Theoretical design of donor-acceptor polymers with low bandgaps, Journal of Molecular Structure (THEOCHEM), 427, 211-219 (1998)., 1998.03.
116. 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.
117. 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.
118. 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.
119. 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.
120. 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.
121. K. Tanaka, H. Ago, Y. Matsuura, T. Kuga, S. Yata, Y. Hato, and N. Ando, ESR study of Li-doped polyacenic semiconductor (PAS) materials, Synthetic Metals, 89, 133-139 (1997)., 1997.08.
122. K. Tanaka, H. Aoki, H. Ago, T. Yamabe, and K. Okahara, Interlayer interaction of two graphene sheets as a model of double-layer carbon nanotube, Carbon, 35, 121-125 (1997)., 1997.05.
123. K. Tanaka, H. Ago, T. Yamabe, K. Okahara, and M. Okada, Bond alternation in carbon nanotubes including s-electrons, International Journal of Quantum Chemistry, 63, 637-644 (1997)., 1997.06.
124. T. Yamabe, K. Tanaka, H. Ago, K. Yoshizawa, and S. Yata, Structure and properties of deeply Li-doped polyacenic semiconductor (PAS), Synthetic Metals, 86, 2411-2414 (1997)., 1997.02.
125. A. K. Bakhshi, H. Ago, K. Yoshizawa, K. Tanaka, and T. Yamabe, Electronic properties of polymers based on thienothiadiazole and thiophene, The Journal of Chemical Physics, 104, 5528-5538 (1996)., 1996.04.
126. K. Tanaka, H. Aoki, H. Ago, and T. Yamabe, Electronic property of polyacene in a constant magnetic field perpendicular to the condensed aromatic-rings plane, Synthetic Metals, 79, 145-148 (1996)., 1996.05.
127. K. Yoshizawa, M. Hatanaka, H. Ago, K. Tanaka, and T. Yamabe, Magnetic properties of 1,3,5-tris[bis(p-methoxyphenyl)amino]benzene cation radicals, Bulletin of the Chemical Society of Japan, 69, 1417-1422 (1996)., 1996.05.
128. A. K. Bakhshi, Y. Yamaguchi, H. Ago, and T. Yamabe, Design of novel donor-acceptor polymers with low band gaps, Synthetic Metals, 79, 115-120 (1996)., 1996.05.
129. A. K. Bakhshi, Y. Yamaguchi, H. Ago, and T. Yamabe, Electronic structures of donor-acceptor polymers based on polythiophene, polyfuran, and polypyrrole, Molecular Engineering, 6, 239-248 (1996)., 1996.03.
130. K. Tanaka, H. Ago, T. Yamabe, J. Li, and K. Kitazawa, An ESR analysis of C60S16, Chemical Physics Letters, 235, 217-220 (1995)., 1995.03.
131. K. Tanaka, H. Ago, and T. Yamabe, Design of ferromagnetic polymers involving organosilicon moieties, Synthetic Metals, 72, 225-229 (1995)., 1995.06.
132. J. Ohshita, T. Watanabe, D. Kanaya, H. Ohsaki, M. Ishikawa, H. Ago, K. Tanaka, and T. Yamabe, Polymeric organosilicon systems. 22: synthesis and photochemical properties of poly[(disilanylene)oligophenylenes] and poly[(silylene)biphenylenes], Organometallics, 13, 5002-5012 (1994), 1994.09.
133. K. Tanaka, H. Ago, T. Yamabe, M. Ishikawa, and T. Ueda, Electronic structures of organosilicon polymers containing thienylene units, Organometallics, 13, 3496-3501 (1994)., 1994.12.

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