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Shimoyama, Iwao; Hakoda, Teruyuki; Baba, Yuji; Sekiguchi, Tetsuhiro; Hirao, Norie; Koswattage, K.
Photon Factory Activity Report 2011, Part B, p.93_1 - 93_2, 2012/00
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
Applied Surface Science, 258(4), p.1561 - 1564, 2011/12
Times Cited Count：6 Percentile：29.25(Chemistry, Physical)Adsorption behavior of atomic deuterium on a hexagonal boron nitride (h-BN) thin film is studied by photon-stimulated ion desorption (PSID) of D
and near edge X-ray absorption fine structure (NEXAFS) at the B and N K-edges. After the adsorption of atomic deuterium, D desorption yield 
(h
) shows clear enhancement at the B K-edge and almost no enhancement at the N K-edge. NEXAFS spectra show a large change in the B K-edge and a small change in the N K-edge after the adsorption. We propose selective adsorption of atomic deuterium on the h-BN thin film based on the experimental results, and mention the effectiveness of applying the PSID method with X-ray to study hydrogen storage materials.
-BN thin filmKoswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
Journal of Chemical Physics, 135(1), p.014706_1 - 014706_12, 2011/07
Times Cited Count：23 Percentile：63.01(Chemistry, Physical)The adsorption of atomic hydrogen on hexagonal boron nitride (-BN) is studied using two element-specific spectroscopies, i.e., near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). B K-edge NEXAFS spectra show a clear change in the energy region of the 
band before and after reaction with atomic deuterium. On the other hand, N K-edge NEXAFS spectra show only a little change. B 1s XPS spectra show a distinct component at the low binding energy side of a main component, while N 1s XPS spectra show peak broadening at the high binding energy side. These experimental results are analyzed by the discrete variational (DV) X
method with a core-hole effect and are explained by a model in which hydrogen atoms are preferentially adsorbed on the B sites of -BN. Based on the experimental and theoretical results, we propose a site-selective property of BN material on adsorption of atomic hydrogen.
Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Narita, Ayumi; Mannan, M. A.*; Koswattage, K.
no journal, ,
Recently much higher-quality thin films are needed in the field of organic semiconductor development. We report on the project started recently: Method to map direction of chemical -bonds in nanometer scale. We are striving to develop a unique instrument to measure polarization-angle dependence of Near-edge X-ray absorption fine structure (NEXAFS) spectra at nano-meter level using photoelectron emission microscopy (PEEM), in order to understand creation and growth mechanisms of oriented domains. It is possible to measure XAFS spectra of microscopic regions magnified by the PEEM scope. The most unique point is the fact that the PEEM column can be rotated along the axis of synchrotron beam, so that one can measure polarization-angle dependences of such micro-XAFS spectra. Moreover, we demonstrate that other experimental and theoretical methods which provide complementary information for chemical and electronic states of organic films.
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji; Nakagawa, Kazumichi*
no journal, ,
Boron nitride (BN) attracts attention for hydrogen storage because of nanotube structure and large interaction with hydrogen. Chemical adsorption of atomic hydrogen is interesting for hydrogen storage at room temperature. However, experimental research on the interaction of atomic hydrogen is little due to the difficulty in synthesizing BN nanomaterials. In this work, we studied adsorption of atomic deuterium on a BN thin film as model system of BN nanotubes with diameter of infinity using NEXAFS spectroscopy. BN thin film was formed on Ni(111) surface by exposure of borazine gas at 800 
C. We measured NEXAFS for the BN film before and after reaction with atomic deuterium produced by a tungsten hot filament. While NEXAFS spectra showed clear change at B K-edge, little change was observed at N K-edge. We analyzed these results by density functional theory calculations and clarified that atomic deuterium preferentially adsorbs on B site in BN materials.
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji; Nakagawa, Kazumichi*
no journal, ,
Boron-nitride (BN) has attracted much attention as a promising candidate for hydrogen storage. Recently, some theoretical efforts have predicted that BN materials have site selectivity on adsorption of atomic hydrogen. However, adsorption structure is still controversial because of inconsistent theoretical reports. In this work, we used NEXAFS and XPS to study adsorption behavior of atomic deuterium on a hexagonal BN thin film as a model system of BN nanotubes. After deuteration, B K-edge NEXAFS spectra showed clear change in between the first * and 
* resonant peaks. On the other hand, N K-edge spectra showed only slight change. XPS of B 1s showed a prominent shoulder on the low binding energy side after deuteration, in contrast to N 1s showed mere peak broadening at the high binding energy side. These results were analyzed by DV-X method. Finally, we concluded that hydrogen is preferentially adsorbed on B sites of BN materials.
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji; Nakagawa, Kazumichi*
no journal, ,
no abstracts in English
Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Narita, Ayumi; Mannan, M. A.*; Koswattage, K.
no journal, ,
We report on a new analytical system we are recently developing in order to clarify creation and growth mechanisms of orientation of organic semiconductors in nano-meter scale. Using the instrument, it is possible to measure polarization angle dependence of X-ray absorption fine structure (XAFS) spectra at nano-meter level using photoelectron emission microscopy; thus, it probes direction of chemical -bonds in nanometer scale. We report on fundamental studies of silicon phthalocyanine thin films, which we first try to clarify orientation mechanism of the organic semiconductor. Samples were prepared by wet-based methods followed by annealing. XAFS spectra and their angle dependent data are well understood by core-excited electronic states calculated under Z+1 approximation model. We have found that one-dimensional polymers are synthesized on the substrate, where phthalocyanine planes are stacked face-to-face, and that the chain axis is perpendicular to the substrate.
Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji; Koswattage, K.
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
no journal, ,
Boron nitride (BN) nanotubes (BNNTs) have attracted much research attention as a promising candidate for hydrogen storage. One of the most basic arguments is the site dependence of atomic hydrogen adsorption. In this work, we investigated the site dependence of atomic deuterium adsorption on a thin film of BN as a representative system for BN nanomaterials, using NEXAFS and XPS. A BN thin. The XPS spectrum of B 1s showed a prominent shoulder on the low binding energy side of the main peak after deuteration, while the N 1s spectrum showed only peak broadening at the high binding energy side. In the PSID measurements, it was observed that there was a clear resonance peak at the B site but no resonance at the N site. The experimental results of NEXAFS and XPS were analyzed by the DV-X method with core-hole effect. Finally, we conclude that deuterium (hydrogen) atoms are preferentially adsorbed on the B sites of BN materials, via a single hydrogen adsorption model.
Koswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji
no journal, ,
no abstracts in English
Koswattage, K.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji
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no abstracts in English
