Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 303

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Absorbent property of fullerene for cesium isotope separation investigated using X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi

Progress in Nuclear Science and Technology (Internet), 5, p.161 - 164, 2018/11

For nuclear transmutation of cesium-135 ($$^{135}$$Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom onto the surface of fullerene (C$$_{60}$$) film has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (XPS). The results were compared with those of CsI. It was found that Cs penetrates into C$$_{60}$$ deep bulk. In contrast, CsI deposits on shallow surface. Furthermore, XPS spectra were measured as a function of Ar$$^{+}$$-sputtering time in order to know Cs concentration profiles in deep region. Results showed that Cs penetrates into deep region of several hundreds ${AA}$.

Journal Articles

Photo-oxidative doping in $$pi$$-conjugated zig-zag chain of carbon atoms with sulfur-functional group

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Applied Physics Letters, 111(23), p.231605_1 - 231605_4, 2017/12

 Times Cited Count:0 Percentile:0(Physics, Applied)

Photo-oxidative doping processes were studied for the trans-polyacetylene (PA) backbone with the -SCH$$_{3}$$ side group as a chemically representative of the S-functionalized zig-zag graphene nanoribbon edge. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy indicates that photochemical reaction of S-CH$$_{3}$$ with atmospheric O$$_{2}$$ forms selectively oxidized products such as -S(O)CH$$_{3}$$ and -SO$$_{3}$$$$^{-}$$ bound to the (PA) backbone. Using the correlation between the oxidation states of sulfur and the XANES peak positions, the partial charge distribution of CH$$_{3}$$S$$^{delta+}$$ -PA$$^{delta-}$$ has been estimated. The results can provide some strategy for area-selective and controllable doping processes of atomic-scale molecular systems with the assistance of UV light.

Journal Articles

Observation of oriented organic semiconductor using Photo-Electron Emission Microscope (PEEM) with polarized synchrotron

Sekiguchi, Tetsuhiro; Baba, Yuji; Hirao, Norie; Honda, Mitsunori; Izumi, Toshinori; Ikeura, Hiromi*

Molecular Crystals and Liquid Crystals, 622(1), p.44 - 49, 2015/12

BB2014-1632.pdf:0.71MB

 Times Cited Count:0 Percentile:0.01(Chemistry, Multidisciplinary)

The molecular orientation is one of the important factors for controlling various properties in organic semiconductor materials. Films are usually heterogeneous. Thus they exist as a mixture of microscopic domains which have a variety of orientation directions. Therefore, it is essential to observe selectively microscopic domains with different orientation direction. In this work, we have developed the photoelectron emission microscopy (PEEM) system combined with the linearly polarized vacuum ultraviolet (VUV) light or synchrotron radiation (SR) X-rays. PEEM images (FOV = ca.50 micro m) for poly(3-hexylthiophene), P3HT thin films were observed under the UV irradiation with various polarization angles, including in-plain and out-of-plain polarization. Morphologies at some bright parts are different each other. The resultant observation suggests that it enables us to distinguish oriented micro-domains with specific directions of polymer chain axis from other amorphous parts.

Journal Articles

Electronic properties of 6,13-Bis(triisopropylsilylethynyl)pentacene probed by inner-shell spectroscopy

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Molecular Crystals and Liquid Crystals, 622(1), p.50 - 54, 2015/12

BB2014-1633.pdf:0.39MB

 Times Cited Count:0 Percentile:0.01(Chemistry, Multidisciplinary)

Organic electrically conducting $$pi$$-stacked molecules are widely regarded as promising materials for future application of nanoelectronics. Direct measurements of electronic structures of unoccupied states in organic semiconductors lead to better understanding of mechanism of electron conduction. For probing unoccupied partial density of states (DOS), X-ray absorption spectroscopy (XAS) is commonly used, where selective excitation of the 1s core electron to the unoccupied conduction band is possible. However, XAS cannot distinguish localized and delocalized features without comparing any theoretical approach. In this work, the core-hole-clock method in resonant Auger spectroscopy (RAS) has been applied to probe electron delocalization through the empty conduction band in the attosecond domain for the purpose of exploring electronic materials with high-speed electron transport. We will discuss some organic molecules such as pentacenes.

Journal Articles

Investigation of unoccupied electronic states near the fermi level of polysilane using resonant Auger spectroscopy

Ogawa, Hiroshi*; Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Molecular Crystals and Liquid Crystals, 622(1), p.164 - 169, 2015/11

 Times Cited Count:0 Percentile:0.01(Chemistry, Multidisciplinary)

Unoccupied electronic states near the Fermi level of poly(dimethylsilane) were probed using Si 1s X-ray absorption spectroscopy (XAS) and Si KL$$_{2,3}$$L$$_{2,3}$$ resonant Auger spectroscopy (RAS). The measured resonance peaks of XAS spectra near Si K-edge have been assigned in comparison with the discrete variational (DV)-X$$alpha$$ molecular orbital calculations. The rapid delocalization of Si 1s core-excited electron through the empty conduction band was observed along the polymer chain with the energy dependent RAS measurement, and the electron delocalization time was estimated based on the core-hole clock method.

Journal Articles

Reconsidering of a polarization rule on atomic arrangements of graphite-like boron carbonitride

Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro

DV-X$$alpha$$ Kenkyu Kyokai Kaiho, 27(1&2), p.34 - 44, 2015/03

no abstracts in English

Journal Articles

A Fluorescence XAFS measurement instrument in the Soft X-ray region toward observation under operando conditions

Honda, Mitsunori; Baba, Yuji; Shimoyama, Iwao; Sekiguchi, Tetsuhiro

Review of Scientific Instruments, 86(3), p.035103_1 - 035103_5, 2015/03

 Times Cited Count:8 Percentile:43.44(Instruments & Instrumentation)

Journal Articles

Structures of quasi-freestanding ultra-thin silicon films deposited on chemically inert surfaces

Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Sekiguchi, Tetsuhiro

Chemical Physics, 444, p.1 - 6, 2014/09

AA2014-0499.pdf:0.68MB

 Times Cited Count:2 Percentile:7.92(Chemistry, Physical)

Silicon thin films were deposited on a sapphire and a highly oriented pyrolytic graphite (HOPG), which have atomically flat and chemically inert surfaces. The electronic and geometrical structures of the films were analyzed by polarization-dependent X-ray absorption fine structure (XAFS). It was found that the silicon K-edge XAFS spectra for ultra-thin silicon films thinner than 0.2 monolayer exhibited two distinct resonance peaks which were not observed for bulk silicon. The peaks were assigned to the resonance excitations from the Si 1s into the valence unoccupied orbitals with $$pi^{*}$$ and $$sigma^{*}$$ characters. The average tilted angle of the $$pi^{*}$$ orbitals was determined by the polarization dependencies of the peak intensities. It was demonstrated that direction of a part of the $$pi^{*}$$ orbitals in silicon film is perpendicular to the surface. These results support the existence of quasi-freestanding single-layered silicon films with sp2 configuration.

Journal Articles

A Polarization rule on atomic arrangements of graphite-like boron carbonitride

Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro

Carbon, 71, p.1 - 10, 2014/05

 Times Cited Count:7 Percentile:29.25(Chemistry, Physical)

B and N K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra of boron carbonitride (B-C-N) films prepared by ion beam deposition are interpreted by molecular orbital calculations with the core-hole effect. Model clusters with different atomic arrangements are compared in terms of photoabsorption cross section (PACS) and net charge, and they are classified into two groups, i.e., polarization and non-polarization types. PACS of $$pi$$$$^{*}$$ peaks near the lowest unoccupied molecular orbital (LUMO) state increase at B K-edge and decrease at N K-edge for polarization type and vice versa for non-polarization type. Based on a comparison between experimental and theoretical results, we propose a rule for atomic arrangements of boron, carbon, and nitrogen atoms in graphite-like B-C-N. Finally, the relationship between the rule and structural stability is discussed.

Journal Articles

Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

Honda, Mitsunori; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

Thin Solid Films, 556, p.307 - 310, 2014/04

 Times Cited Count:5 Percentile:27.7(Materials Science, Multidisciplinary)

Journal Articles

Structure of ultra-thin silicon film on HOPG studied by polarization-dependence of X-ray absorption fine structure

Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Sekiguchi, Tetsuhiro

Chemical Physics Letters, 594, p.64 - 68, 2014/02

 Times Cited Count:2 Percentile:7.92(Chemistry, Physical)

Structures of mono-layered silicon on a highly oriented pyrolytic graphite (HOPG) have been investigated by X-ray photoelectron spectroscopy and X-ray absorption near edge structure (XANES). For the Si K-edge XANES spectrum of the 0.15 mono-layered film, two distinct peaks were observed, which were assigned to the resonant excitations from the Si 1s into the valence unoccupied orbitals with $$pi$$$$^{*}$$ and $$sigma$$$$^{*}$$ characters. On the basis of the polarization dependences of the peak intensities, it was concluded that a part of the Si film lies flat on the HOPG surface, which supports the existence of two-dimensional graphene-like structure in mono-layered silicon.

Journal Articles

Molecular ordering effect of regioregular poly(3-hexylthiophene) using sulfur K-edge X-ray absorption spectroscopy

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Japanese Journal of Applied Physics, 53(2S), p.02BB07_1 - 02BB07_4, 2014/02

 Times Cited Count:11 Percentile:50.47(Physics, Applied)

The electronic structure of the unoccupied conduction band of regioregular poly(3-hexylthiophene) (RR-P3HT) was investigated by X-ray absorption spectroscopy (XAS) near the sulfur K-edge. Angle-dependent XAS studies revealed that polymer chains in films are well aligned and oriented edge-on with respect to the Si substrate. It was clearly observed that the bottom of the conduction band near the Fermi level in a $$pi$$-$$pi$$ stacking film is lower (0.3 eV) than that in a powder. It was demonstrated that $$pi$$-$$pi$$ stacking interactions improve the power conversion efficiency through the reduction of the lowest unoccupied molecular orbital (LUMO) energy level.

Journal Articles

Focusing of soft X-rays using poly-capillary with precise adjustment mechanism and its application to quick chemical-state analysis

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao

Bunseki Kagaku, 63(1), p.53 - 58, 2014/01

AA2013-0769.pdf:1.16MB

 Times Cited Count:0 Percentile:0(Chemistry, Analytical)

A method for quick and real-time observations of a solid surface at nanometer scale is described. The principle of the method is as follows. Soft X-rays from a synchrotron light source are irradiated on a solid surface and the total photoelectrons are expanded and focused on a screen using electrostatic lenses. When the energy of X-rays is scanned and the brightness is plotted, we can obtain micro X-ray absorption (micro-XAFS) spectra in all regions of the image. The spacial resolution of the method was 40 nm. In order to more quickly observe a microscopic image and measure micro-XAFS spectra, the soft X-rays from the bending magnet were focused using a newly developed poly-capillary. As a result, the photon flux of 3 keV X-rays was increased about 60 time higher than that before the focusing. Using focused X-rays, we succeeded in observing one image at 10 ms for a bulk sample. We have also tried to shorten the measuring time of the micro-XAFS spectrum. For a Si-SiO$$_{2}$$ sample, it has been demonstrated that micro-XAFS spectra in all regions of an image can be obtained within 1 min. It is concluded that real-time observations of chemical-states at nanometer scale are possible by the present method.

Journal Articles

Orientation effect of organic semiconducting polymer revealed using Photo-Electron Emission Microscope (PEEM)

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Honda, Mitsunori; Izumi, Toshinori; Ikeura, Hiromi*

Photon Factory Activity Report 2013, Part B, P. 546, 2014/00

The molecular orientation is one of the important factors for controlling various properties in organic semiconductor materials. Films are usually heterogeneous. Thus they exist as a mixture of microscopic domains which have a variety of orientation directions. Therefore, it is essential to observe selectively microscopic domains with different orientation direction. In this work, we have developed the photoelectron emission microscope (PEEM) system combined with the linearly polarized vacuum ultraviolet (VUV) light or synchrotron radiation (SR) X-rays. PEEM images for poly(3-hexylthiophene), P3HT thin films were observed under synchrotron X-ray irradiation with linearly polarization. In conclusion, it was found that PEEM with polarized synchrotron can be a powerful tool that gives information of molecular orientation in nano-meter scale.

Journal Articles

Molecular orientation of pentacene derivative

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Photon Factory Activity Report 2013, Part B, P. 518, 2014/00

Organic electrically conducting $$pi$$-stacked small molecules are widely regarded as promising materials for future application of low-cost and flexible nanoelectronics. Pentacene is one of the most promising organic semiconductors because of its excellent device performance. Direct measurements of electronic structures of unoccupied states of organic semiconductors lead to better understanding of mechanism of electron conduction. For probing unoccupied partial density of states (DOS), X-ray absorption spectroscopy (XAS) is commonly used, where selective excitation of the 1s core electron to the unoccupied conduction band is possible. The molecular orientation of pentacene derivative has been investigated by angle dependent XAS measurements. Electronic states were calculated by DVX$$alpha$$ method.

Journal Articles

Electronic structures of silicon monoxide film probed by X-ray absorption spectroscopy

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

Surface Science, 612, p.77 - 81, 2013/06

 Times Cited Count:8 Percentile:41.17(Chemistry, Physical)

Electronic structures of thin films of silicon monoxides (SiO) deposited on a solid surface have been in-situ investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS). For thin films with less than monolayer on highly oriented pyrolytic graphite (HOPG), it was elucidated that the stable divalent silicon surely exists in the deposited SiO layer. For the Si K-edge XAFS spectrum of the SiO thin film, the energy of the core-to-valence resonance peak is located between those of the elemental silicon (Si$$^{0}$$) and SiO$$_{2}$$ (Si$$^{4+}$$). The polarization dependence of the Si K-edge XAFS spectra revealed that the SiO molecules are well-ordered and almost perpendicularly oriented on HOPG surface. The obtained well-ordered SiO films with divalent silicon will become an excellent starting material for the synthesis of low-dimensional SiO$$_{rm x}$$ films.

Journal Articles

Orientation of silicon phthalocyanine thin films revealed using polarized X-ray absorption spectroscopy

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Honda, Mitsunori; Deng, J.*

Photon Factory Activity Report 2012, Part B, P. 68, 2013/00

The orientation of organic semiconducting molecules on surfaces plays a crucial role in improving the properties of electronic devices. We prepared thin films of silicon phthalocyanine dichroride (SiPcCl$$_{2}$$) on graphite spin-cast followed by heating to 350$$^{circ}$$C at ambient condition. We investigate the molecular orientation of the films using angle-dependent near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. Si 1s NEXAFS spectra for the thin films after annealing are very different each other, indicating that the corresponding reactions thus the structures of final products are different. The structures of the reaction products are estimated with the help of ab initio molecular orbital calculations that fit the observed NEXAFS spectra.

Journal Articles

Electronic structure of regioregular poly(3-hexylthiophene)

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Photon Factory Activity Report 2012, Part B, P. 118, 2013/00

We have investigated the electronic property of RR-P3HT (regioregular-poly(3-hexylthiophene)) films with $$pi$$-$$pi$$ stacking using sulfur K-edge X-ray absorption fine structure (XAFS) spectroscopy. It was observed that the LUMO of $$pi$$-$$pi$$ stacking film is lower in energy by 0.3 eV than that of the polycrystalline powder, although these compounds are the same origin. This shift was explained that the interaction between the two molecules in co-facial leads to splitting of the LUMO level to LUMO and LUMO+1, resulting in reduced LUMO energy.

Journal Articles

Immobilization of alkyl chain molecules on oxide surface using phosphonic acid as an anchor

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Yaita, Tsuyoshi

e-Journal of Surface Science and Nanotechnology (Internet), 10, p.367 - 373, 2012/07

To apply organic thin films as new devices, it is important to immobilize organic molecules on oxide surfaces. In this study, we investigated the formation of organic self-assembled monolayer on the oxide surface. Decyl phosphonic acid (DPA) molecules were used as the adsorbed molecule on the surface. The DPA film was prepared by immersing the sapphire substrate in DPA ethanol solution. The sample was measured by XPS using synchrotron soft X-ray. For the P 1s XPS spectra of the DPA powder and the DPA film on the sapphire surface, a single peak was observed and the binding energies of the two samples were almost the same. And we measured the sample by the total reflection (TR) XPS, which is highly surface sensitive method. Compared with the normal XPS, the intensity of the C 1s peak in TR-XPS was enhanced. As a result, it was elucidated that the phosphonic acid of the DPA molecule was located at the lower side, while the alkyl chain was located at the upper side on the surface.

Journal Articles

Formation of boron nitride ultra-thin films on Si(111)

Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.*

Physica Status Solidi (C), 9(6), p.1450 - 1453, 2012/06

 Times Cited Count:2 Percentile:66.99

no abstracts in English

303 (Records 1-20 displayed on this page)