Orientation of one-dimensional silicon polymer films studied by polarization-dependent NEXAFS

Mannan, M. A.*; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Nagano, Masamitsu*; Noguchi, Hideyuki*

Photon Factory Activity Report 2011, Part B, P. 159, 2012/00

http://pfwww.kek.jp/acr2011pdf/part_b/pf11b159.pdf

no abstracts in English

Self-ordering of silicon polymer thin film grown on indium tin oxide surface investigated by X-ray absorption spectroscopy

Mannan, M. A.*; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Narita, Ayumi; Nagano, Masamitsu*; Noguchi, Hideyuki*

Journal of Electron Spectroscopy and Related Phenomena, 181(2-3), p.242 - 248, 2010/08

https://doi.org/10.1016/j.elspec.2010.02.014

The ordering and molecular orientation of polydimethylsilane (PDMS) films grown on indium tin oxide (ITO) surface has been assigned. The orientation of the samples as well as that of the annealed sample was studied by Si K-edge near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy using linearly polarized synchrotron radiation. The Si K-edge NEXAFS spectra for the thick film have at least four resonance peaks of which two peaks are found to be strongly polarization dependent. On the basis of the polarization dependences of the peak intensities, it is revealed that the backbones of the PDMS films are perpendicularly oriented on the ITO surface. The angle between surface and the Si-Si bonds for multilayered film calculated from the helical structure of PDMS molecule was found to be 41.5 which was almost coincided with the experimentally obtained angle of 40 . It was concluded that PDMS molecules are highly self-ordered on ITO surface.

ESR method for detecting irradiated fresh mangoes

Kikuchi, Masahiro; Hussain, M. S.*; Morishita, Norio; Sakashita, Tetsuya; Funayama, Tomoo; Ukai, Mitsuko*; Shimoyama, Yuhei*; Kobayashi, Yasuhiko

JAEA-Review 2009-041, JAEA Takasaki Annual Report 2008, P. 86, 2009/12

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2009-041.pdf

When tropical fruits are imported, quarantine treatments are required for preventing plant pests. The irradiation is a choice of the quarantine treatments for tropical fruits in the world. When the irradiation is utilized as the treatment, detection methods are required to endorse the reliability of labels for consumers. To distinguish the irradiated fresh mangoes from non-irradiated ones, radical detection was carried out using ESR. After freeze-drying mangoes, the ESR main peak was observed but the signal intensity was affected by ripeness and period of storage. We found that the existence of side peaks is an effective indicator to detect fresh mangoes irradiated to dose range of quarantine treatment. Since ESR method is able to measure without complicate preparation, this technique is useful to detect the irradiation treatment against a wide variety of foods.

Atomic arrangement, composition and orientation of hexagonal BCN films synthesized by radiofrequency plasma enhanced CVD

Mannan, M. A.*; Kida, Tetsuya*; Noguchi, Hideyuki*; Nagano, Masamitsu*; Shimoyama, Iwao; Hirao, Norie; Baba, Yuji

Journal of the Ceramic Society of Japan, 117(1364), p.503 - 507, 2009/04

https://doi.org/10.2109/jcersj2.117.503

Oriented hexagonal BCN films were synthesized on Si(100) substrate by radiofrequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane as a precursor. The formation of the crystalline hexagonal BCN hybrids was confirmed by FT-IR and XRD. CH + H carrier gas increased the C content in the films in comparison with N carrier gas. XPS measurement showed that the films were composed of a variety of B-N, B-C, C-N bonds to form the BCN atomic hybrids. The resonance peak in the B K-edge NEXAFS spectra also indicated the presence of the hybrid configuration of B-C-N bonds like BN in h-BN. The resonance peaks suggested the diversity in the bonds in the films. Orientation of the h-BCN hybrids was suggested on the basis of the polarization dependence of NEXAFS.

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

Substitution effect on orientation of organosilicon compounds (CH)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

https://doi.org/10.1088/0953-8984/17/36/002

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)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.

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

https://doi.org/10.1016/j.apsusc.2004.09.040

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 C. An ultrahigh vacuum (UHV) chamber with base pressure 10 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 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.

Detection of desorbed ions from the top surface using angle-dependent detector

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

no journal, , 

We have constructed a novel rotatable time-of-flight (TOF) mass detector for desorbed fragment-ions produced by irradiation of synchrotron radiation (SR). This makes the best use of advantages in synchrotron, including variable X-ray energy, linear polarization, and pulsed capability. The detector allows us to measure excitation-energy dependences of desorbing ion yields from solid surfaces in a variety of incident angles of X-ray beams. We propose that this angle-dependent technique provides insights into orientation of chemical bonds lying at the top surface. The present paper reports our recent findings that the mass-patterns and yields of desorbed ions drastically depend on the incident angles less than 10 degrees. The results suggest that direct desorption mechanism prevails in extremely small angles and indirect desorption mechanism induced through collision excitation by secondary electrons is suppressed.

Coordination and configuration analysis of local structures of B-C-N hybrid thin films

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

no journal, , 

Graphite-like B-C-N hybrids have been expected to control a wide variety of electronic properties from metal to insulator. However, since most B-C-N hybrids have complex structure including various unknown chemical bonding states, the local structures have not been clarified yet. In order to clarify the chemical bonding states of this material, we measured near-edge X-ray absorption fine structure (NEXAFS) of B-C-N hybrid thin films. B-C-N hybrid thin films were synthesized by ion beam deposition of borazine on a graphite substrate, and the composition was controlled by ion fluence. Some * peaks were observed in B and N K-edge NEXAFS spectra, and relative intensities of the peaks depended on ion fluence and polarization. Electronic structures of some model clusters are calculated by a molecular orbital theory, and compared with NEXAFS spectra. From the experimental and theoretical results, we discuss some models of local structures.

Structure analysis of B-C-N hybrid thin films by inner-shell excitation spectroscopy

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

no journal, , 

B-C-N hybrids have been expected to be used for an alternative catalysis for Pt. Since most products have complex structure including various unknown chemical bonding states, the local structures have not been clarified yet. In order to clarify the chemical bonding states of this material, we measured near-edge X-ray absorption fine structure (NEXAFS) of B-C-N hybrid thin films. B-C-N hybrid thin films were synthesized by ion beam deposition of borazine on a graphite substrate. Some * peaks were observed in B and N K-edge NEXAFS spectra, and these peaks showed different polarization dependences. This suggests that buckled structures were formed with graphite-like planner structures. Heat of formation is calculated for some model clusters which consist of a pentagon and hexagons, and compared with that for planner clusters with same compositions. From the comparison, we propose that substitution of B and N atoms for C atoms in graphite can induce fullerene-like structure.