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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

Journal Articles

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Kataoka, Takashi*; Kobayashi, Masaki*; Sakamoto, Yuta*; Song, G. S.*; Fujimori, Atsushi*; Chang, F.-H.*; Lin, H.-J.*; Huang, D. J.*; Chen, C. T.*; Okochi, Takuo*; et al.

Journal of Applied Physics, 107(3), p.033718_1 - 033718_7, 2010/02

AA2009-0977.pdf:1.0MB

 Times Cited Count:49 Percentile:86.61(Physics, Applied)

Journal Articles

Localization of electrons in the sugar/phosphate backbone in DNA investigated via resonant Auger decay spectra

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

Physical Review B, 74(20), p.205433_1 - 205433_5, 2006/11

 Times Cited Count:4 Percentile:23.8(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Preparation and characterization of B-C-N hybrid thin films

Uddin, M. N.*; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Nath, K. G.*; Baba, Yuji; Nagano, Masamitsu*

JAEA-Research 2006-034, 72 Pages, 2006/06

JAEA-Research-2006-034.pdf:4.05MB

no abstracts in English

Journal Articles

Synthesis and characterization of oriented graphitelike B-C-N hybrid

Uddin, M. N.*; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.*; Nagano, Masamitsu*

Journal of Applied Physics, 99(8), p.084902_1 - 084902_5, 2006/04

 Times Cited Count:4 Percentile:17.99(Physics, Applied)

no abstracts in English

Journal Articles

Characterization of F$$^{+}$$-irradiated graphite surfaces using photon-stimulated desorption spectroscopy

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

Surface and Interface Analysis, 38(4), p.352 - 356, 2006/04

 Times Cited Count:3 Percentile:8.09(Chemistry, Physical)

We investigated the orientation nature at the top-most layers of F$$^{+}$$-irradiated graphite using polarization dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy which incorporates partial electron yield (PEY) detection and photon-stimulated ion desorption (PSID) techniques. The fluorine K-edge NEXAFS spectra conducted in PEY mode show no significant dependence on polarization angles. In contrast, NEXAFS spectra recorded in F$$^{+}$$ ion yield mode show enhanced yields at a feature of $$sim$$689.4 eV assigned as a $$sigma$$*(C-F) state relevant to =C-F sites, which depend on polarization angles. The C-F bonds prefer relatively tilting down the surface at the top-most layer, while the C-F bonds are randomly directed at deeper regions. We conclude that the difference in the orientation structures between the top surface and bulk is reflected in the NEXAFS recorded in the two different detection modes. It was also found that H$$^{+}$$- and F$$^{2+}$$- PSID NEXAFS spectra are helpful in understanding desorption mechanism, thus in analysing NEXAFS data.

Journal Articles

Substitution effect on orientation of organosilicon compounds (CH$$_{3}$$)$$_{3}$$SiX (X = F, Cl, Br, I, NCO) as studied using NEXAFS spectroscopy

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

Journal of Physics; Condensed Matter, 17(36), p.5453 - 5466, 2005/09

 Times Cited Count:1 Percentile:6.58(Physics, Condensed Matter)

The orientation nature of multilayer organosilicon compounds has been investigated by measuring the dependence of the Si K-shell near-edge X-ray absorption fine structures (NEXAFS) on the polarization angle. Two approaches helped to elucidate the orientation mechanism: the substitution effect and the deposition-rate dependence. The orientation angles of Si-X bond axes were obtained for trimethylsilyl halides, (CH$$_{3}$$)$$_{3}$$SiX (X =F Cl Br I NCO, condensed on Cu(111) at a low (82 K) temperature: the angles are 60, 73, 61, 55, and 55 degrees with respect to the surface normal, for X =F, Cl, Br, I, and NCO, respectively. Chloride (X =Cl) produces the most parallel tilt angle. The specific orientation nature of chloride is attributed to its strong dipole moment as well as the regular tetrahedron shape of the molecule. The molecular volumes calculated verify this view. Furthermore, deposition rates are found to greatly influence the growth manner: namely, high deposition rates led to a slightly perpendicular orientation of Si-X bond axis.

Journal Articles

Local bonding states of ion-irradiated graphite characterized by photon-stimulated desorption (PSD) spectroscopy

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

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.437 - 441, 2005/06

 Times Cited Count:3 Percentile:18.36(Spectroscopy)

no abstracts in English

Journal Articles

Synchrotron radiation photoabsorption and photoemission spectroscopy for thermal-induced reoriented Si polymer

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

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.323 - 326, 2005/06

 Times Cited Count:5 Percentile:28.59(Spectroscopy)

The effect of laser annealing on electronic atructures and molecular orientation for poly(dimethylsilane), {PDMS, [Si(CH$$_{3}$$)$$_{2}$$]$$_{n}$$} has been studied by synchrotron radiation photoemission and photoabsorption spectroscopy. Prior to annealing, PDMS powder was mounted on the basal plane of highly oriented pyrolytic graphite. Both Si 1s X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at Si 1s edge show that electronic structures have been modified due to annealing. Furthermore, the angle-dependent NEXAFS spectra clearly indicate that the annealed products maintain a specific orientation. Interestingly, no such kind of orientation is present in as-received PDMS powder as no angle-dependency is observed before annealing.

Journal Articles

B-C-N hybrid synthesis by high-temperature ion implantation

Uddin, M. N.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.; Nagano, Masamitsu*

Applied Surface Science, 241(1-2), p.246 - 249, 2005/01

 Times Cited Count:8 Percentile:38.49(Chemistry, Physical)

Recently, much attention has been given on the synthesis and characterization of graphite-like B-C-N hybrid. Since graphite-like B-C-N hybrid may have semiconducting property, this material is interesting for applications to electronic and luminescent devices. In order to synthesize this material, borazine ion plasma was implanted in graphite at room temperature (RT) and 600 $$^{circ}$$C. An ultrahigh vacuum (UHV) chamber with base pressure $$sim$$10$$^{-7}$$ Pa was used for the experiment. The X-ray photoelectron spectroscopy (XPS) study suggested that B atoms in the deposited films are in a wide variety of atomic environment such as BC3, BN3 and B-C-N hybrid. The ratios of these coordinations strongly depend on the temperature during the ion implantation. It was found that the B-C-N hybrid is predominantly synthesized by the implantation at 600 $$^{circ}$$C where the surface [B]/([B]+[C]+[N]) ratio ranges from 0.1 to 0.35. The results imply that it is possible to control the composition of B-C-N hybrid by changing the fluence of the ion plasma and the temperature of graphite during ion implantation.

Journal Articles

Structure of sub-monolayered silicon carbide films

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

Applied Surface Science, 237(1-4), p.176 - 180, 2004/10

 Times Cited Count:7 Percentile:38.81(Chemistry, Physical)

no abstracts in English

Journal Articles

Electronic structure analysis of a $$h$$-BN thin film on Ni(111) using NEXAFS spectroscopy

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

Hyomen Kagaku, 25(9), p.555 - 561, 2004/09

no abstracts in English

Journal Articles

Electronic structures of ultra-thin silicon carbides deposited on graphite

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

Applied Surface Science, 234(1-4), p.246 - 250, 2004/07

 Times Cited Count:8 Percentile:42.35(Chemistry, Physical)

no abstracts in English

Journal Articles

Study of the oxidation for Si nanostructures using synchrotron radiation photoemission spectroscopy

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

Applied Surface Science, 234(1-4), p.234 - 239, 2004/07

 Times Cited Count:6 Percentile:35.11(Chemistry, Physical)

Here we report oxidization properties of Si nanostructures grown on graphite. Si 1s X-ray photoemission spectra using synchrotron radiation are used in order to understand the oxidization pathways. Several Si films, such as 0.4, 2, 5.5 & Aring; were grown on highly oriented pyrolitic graphite (HOPG). In the case of a 0.4 & Aring; Si on HOPG, where different types of Si nanostructures in the form of nanoclusters are present, oxygen reactivity is nearly zero. In contrast, the thick film (5.5 & Aring;), where a bulk-type phase is present, shows a higher degree of reactivity. The results are discussed on the basis of nanostructure geometry, number of constituting Si atoms and cluster size.

Journal Articles

NEXAFS spectra of an epitaxial boron nitride film on Ni(111)

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

Journal of Electron Spectroscopy and Related Phenomena, 137-140, p.573 - 578, 2004/07

 Times Cited Count:25 Percentile:70.72(Spectroscopy)

Hexagonal boron nitride (h-BN) thin film has been epitaxially formed on Ni(111) by chemical vapor deposition using borazine gas. The electronic structure of this system is studied by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). The thickness of the h-BN is estimated to be about two-layers from XPS. B K-edge NEXAFS spectra show new $$pi$$* peak which is not observed in the spectrum for bulk h-BN. From a polarization dependence analysis of NEXAFS, we propose this new $$pi$$* peak originates from the interaction between the h-BN and Ni(111). This new $$pi$$* peak clearly proves that conduction band of h-BN/Ni(111) is different from that of bulk h-BN.

Journal Articles

Fragmentation pathways caused by soft X-ray irradiation; The detection of desorption products using a rotatable time-of-flight mass-spectrometer combined with pulsed synchrotron radiation

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

Free Electron lasers 2003, p.II_69 - II_70, 2004/00

no abstracts in English

Journal Articles

Characterization of B-C-N hybrid prepared by ion implantation

Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.; Sasaki, Masayoshi*; Okuno, Kenji*

Journal of Vacuum Science and Technology A, 21(6), p.1843 - 1848, 2003/11

 Times Cited Count:6 Percentile:29.19(Materials Science, Coatings & Films)

Ion implantation method is applied to synthesize B-C-N hybrids and their electronic structures are characterized by X-ray photoelectron spectroscopy. A boron nitride film is deposited on a graphite target by borazine plasma implantation. At the interface between the BN film and the graphite, variety of bonding combinations including B-N, B-C, and C-N are observed. This proved that B-C-N hybrids is formed by this method.

Journal Articles

Element- and orientation-selective photo-fragmentation using polarized synchrotron radiation

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

Photon Factory Activity Report 2002, Part B, P. 80, 2003/11

no abstracts in English

Journal Articles

Chemical-state analysis for low-dimensional Si and Ge films on graphite

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

Journal of Applied Physics, 94(7), p.4583 - 4588, 2003/10

 Times Cited Count:15 Percentile:53.57(Physics, Applied)

no abstracts in English

Oral presentation

Structures of low-dimensional silicon-carbon mixed systems

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

no journal, , 

no abstracts in English

29 (Records 1-20 displayed on this page)