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Journal Articles

Gas barrier properties of chemical vapor-deposited graphene to oxygen imparted with sub-electronvolt kinetic energy

Ogawa, Shuichi*; Yamaguchi, Hisato*; Holby, E. F.*; Yamada, Takatoshi*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Journal of Physical Chemistry Letters (Internet), 11(21), p.9159 - 9164, 2020/11

 Times Cited Count:2 Percentile:42.52(Chemistry, Physical)

Atomically thin layers of graphene have been proposed to protect surfaces through the direct blocking of corrosion reactants such as oxygen with low added weight. The long term efficacy of such an approach, however, is unclear due to the long-term desired protection of decades and the presence of defects in as-synthesized materials. Here, we demonstrate catalytic permeation of oxygen molecules through previously-described impermeable graphene by imparting sub-eV kinetic energy to molecules. These molecules represent a small fraction of a thermal distribution thus this exposure serves as an accelerated stress test for understanding decades-long exposures. The permeation rate of the energized molecules increased 2 orders of magnitude compared to their non-energized counterpart. Graphene maintained its relative impermeability to non-energized oxygen molecules even after the permeation of energized molecules indicating that the process is non-destructive and a fundamental property of the exposed material.

Journal Articles

Valence-band electronic structure evolution of graphene oxide upon thermal annealing for optoelectronics

Yamaguchi, Hisato*; Ogawa, Shuichi*; Watanabe, Daiki*; Hozumi, Hideaki*; Gao, Y.*; Eda, Goki*; Mattevi, C.*; Fujita, Takeshi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; et al.

Physica Status Solidi (A), 213(9), p.2380 - 2386, 2016/09

 Times Cited Count:8 Percentile:46.1(Materials Science, Multidisciplinary)

We report valence-band electronic structure evolution of graphene oxide (GO) upon its thermal reduction. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored using real-time ultraviolet photoelectron spectroscopy. We observed a drastic increase in the density of states around the Fermi level upon thermal annealing at $$sim$$ 600$$^{circ}$$C. The result indicates that while there is an apparent bandgap for GO prior to a thermal reduction, the gap closes after an annealing around that temperature. This trend of bandgap closure was correlated with the electrical, chemical, and structural properties to determine a set of GO material properties that is optimal for optoelectronics. The results revealed that annealing at a temperature of 500$$^{circ}$$C leads to the desired properties, demonstrated by a uniform and an order of magnitude enhanced photocurrent map of an individual GO sheet compared to an as-synthesized counterpart.

Journal Articles

Graphene growth and carbon diffusion process during vacuum heating on Cu(111)/Al$$_{2}$$O$$_{3}$$ substrates

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

Japanese Journal of Applied Physics, 52(11), p.110122_1 - 110122_8, 2013/11

 Times Cited Count:17 Percentile:63.5(Physics, Applied)

Journal Articles

Vacuum annealing formation of graphene on diamond C(111) surfaces studied by real-time photoelectron spectroscopy

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

Japanese Journal of Applied Physics, 51(11), p.11PF02_1 - 11PF02_7, 2012/11

 Times Cited Count:23 Percentile:70.04(Physics, Applied)

Journal Articles

Observation of graphene-on-diamond formation studied by real-time photoelectron spectroscopy

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Watanabe, Daiki*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

Hyomen Kagaku, 33(8), p.449 - 454, 2012/08

Graphene-on-insulator structures are required for fabrication of the graphene transistor. Diamond has been attracted as the substrate for graphene growth because it has a larger band gap and break down voltage compared with SiC. The detail of graphitization on a diamond surface has not been clarified yet because the nondestructive evaluation for graphene-on-diamond (GOD) structure was hard. In this study, we have developed an evaluation method of GOD based on the photoemission spectroscopy using synchrotron radiation focusing the shift of photoelectron spectra due to band bending. We can clearly determine the graphitization temperature on the diamond C(111) surface as approximately 1120 K, which is lower than that on an SiC substrate. It is also confirmed from C 1s photoelectron spectra, there is the buffer layer at the interface between the grapheme layer and the diamond substrate.

Oral presentation

Investigation of deposit condition in the first stage of $$beta$$-FeSi$$_{2}$$ homoepitaxial growth

Wakaya, Ippei*; Ochiai, Kunihito*; Udono, Haruhiko*; Nagano, Takatoshi*; Yamada, Yoichi; Yamamoto, Hiroyuki; Esaka, Fumitaka

no journal, , 

Deposit condition in the first stage of $$beta$$-FeSi$$_{2}$$ homoepitaxial growth has been investigated.

Oral presentation

Development of simplified pelletizing process for fast reactor MOX fuels, 3; Development of die wall lubrication pressing method

Sudo, Katsuo; Okita, Takatoshi; Takeuchi, Kentaro; Takano, Tatsuo; Kato, Akebumi*; Haga, Tetsuya; Yamada, Yoshikazu; Kihara, Yoshiyuki

no journal, , 

no abstracts in English

Oral presentation

Real-time synchrotron radiation photoelectron spectroscopic observation of high temperature thermal anneal processes of oxidized graphene

Hozumi, Hideaki*; Yamaguchi, Hisato*; Kaga, Toshihide*; Eda, Goki*; Mattevi, C.*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

In order to clarify the time evolution of the chemical bonding state during thermal reduction of graphene oxide (GO), real-time photoelectron spectroscopy was employed for observing the thermal reduction kinetics of GO. The GO was prepared by the modified Hummer method. The experiments were performed using the surface reaction analysis apparatus placed at the BL23SU of SPring-8. The XPS measurements were performed simultaneously during the annealing at 473 K, 673 K, 873 K, and 1073 K. The C1s photoelectron spectra are decomposed by 8 components. The $$pi$$-$$pi^*$$ transition loss peak intensity is propotional to the intensity of sp$$^{2}$$ graphene components with temperature elevation. In addition, defect intensity increased in proportion with the sp$$^{2}$$ graphene intensity. These facts indicate that defects were formed on the graphene during reduction and these defects cause the recovery of electric conductivity, that is, the appearance of Fermi edge.

Oral presentation

Real time XPS observation of oxidized graphene reduction processes

Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Kaga, Toshihide*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Temperature dependence of chemical bonding states during annealing on diamond (111) surfaces

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Kaga, Toshihide*; Hozumi, Hideaki*; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Formation of graphene on diamond C(111) surfaces by vacuum annealing

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Kaga, Toshiteru*; Hozumi, Hideaki*; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

Oral presentation

Observation of graphen-on-diamond formation processes by real-time photoelectron spectroscopy

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Vacuum annealing formation of graphene on diamond C(111) surfaces studied by real-time photoelectron spectroscopy

Ogawa, Shuichi*; Yamada, Takatoshi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Watanabe, Daiki*; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

Oral presentation

Photoelectron spectroscopic observation of formation of graphene-on-diamond structure made by thermal annealing in vacuum

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Watanabe, Daiki*; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Real-time XPS study of reduction of graphene oxide; Effect of hydrazine treatment

Watanabe, Daiki*; Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Photoelectron spectroscopic observation of thermal annealing processes in vacuum for graphene oxide treated by hydrazine

Watanabe, Daiki*; Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Chemical bonding states and electronic states of reduced graphene oxides studied by real-time photoelectron spectroscopy

Watanabe, Daiki*; Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

Oral presentation

In-situ photoelectron spectroscoic observation of graphene formation processes by control of diamond single crystal surface C(001)

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Real-time photoelectron spectroscopic analysis of chemical bonding states in reduction processes of graphene oxides

Watanabe, Daiki*; Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Effects of hydrazine processing in reduction of oxidized graphene

Watanabe, Daiki*; Ogawa, Shuichi*; Yamaguchi, Hisato*; Hozumi, Hideaki*; Eda, Goki*; Mattevi, C.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; et al.

no journal, , 

no abstracts in English

29 (Records 1-20 displayed on this page)