Polarization dependence of soft X-ray absorption spectroscopy on the heavy fermion superconductor CeNiGe

Fujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Sekiyama, Akira*; Tanaka, Arata*; Ebihara, Takao*; et al.

New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12

https://doi.org/10.3938/NPSM.73.1062

Fundamental research of X-ray absorption imaging for elemental identification using a secondary target

Nakae, Masanori*; Matsuyama, Tsugufumi*; Murakami, Masashi; Yoshida, Yukihiko; Machida, Masahiko; Tsuji, Koichi*

Advances in X-Ray Chemical Analysis, Japan, 54, p.89 - 99, 2023/03

Fundamental research on X-ray absorption imaging for elemental identification was studied. A secondary target was applied to obtain X-ray absorption images above and below the X-ray absorption edge of the target element. X-rays from an X-ray tube were irradiated to the secondary target, where the characteristic X-rays were emitted that were irradiated to the sample. X-ray absorption images were acquired with an exposure time of a few seconds with an X-ray camera. In this technique, it is difficult to change the energy of X-rays as we want, however we can apply this technique for imaging the specific element. Metal foil sample composed of Al, Cu, and Ni was analyzed. To obtain an X-ray elemental image of Ni, two X-ray absorption images were taken using the X-rays above and below the Ni K-edge. X-rays of Cu K and Zn K were prepared by using Cu and Zn plates as the secondary target. Finally, the Ni elemental image was obtained by subtracting two images. Furthermore, the X-ray camera had a function of setting critical energies for imaging, thus it was demonstrated that an X-ray elemental image of Ni was obtained using a single secondary target without changing the secondary target.

X-ray absorption spectroscopy and magnetocaloric study of PrSrCoO (00.5)

Matsumura, Daiju; Tsuji, Takuya; Yoshii, Kenji

Materials Chemistry and Physics, 238, p.121885_1 - 121885_5, 2019/12

https://doi.org/10.1016/j.matchemphys.2019.121885

We have conducted X-ray absorption spectroscopy study for perovskite cobaltite PrSrCoO (00.5) to understand Sr doping effect and magnetocaloric measurement for PrSrCoO to reveal the origin of magnetic anomaly at around 110 K. The extended X-ray absorption fine structure (EXAFS) measurements at the Co -edge suggest that the average valence value of Co ions increases, the interatomic distance of Co-O bonding decreases, and the local distortion of CoO octahedron increases as Sr is doped in PrCoO. The interatomic distance of Co-O bonding shrinks more greatly for the larger doping region. No temperature dependent electronic and structural changes were observed from Co -edge X-ray absorption spectra in the whole thermal range studied (17-300 K). The magnetocaloric effect of PrSrCoO indicates the change of magnetic structure at 110 K.

In Situ Time-Resolved XAFS Studies on Laser-induced Particle Formation of Palladium Metal in an Aqueous/EtOH solution

Saeki, Morihisa*; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 123(1), p.817 - 824, 2019/01

https://doi.org/10.1021/acs.jpcc.8b09532

Reaction kinetics of laser-induced particle formation in an aqueous solution of PdCl was investigated by transmission electron microscope (TEM) and dispersive X-ray absorption fine structure (DXAFS). The Pd particle was generated by irradiation of nanosecond pulsed 266-nm laser. The TEM observation showed dependence of the particle size on the laser fluence and promotion of the particle growth by irradiation of high-fluence laser. The DXAFS data give us the Pd concentration. Temporal changes of the Pd concentration analyzed based on Finke-Watzky two step mechanism. The analysis elucidates that the laser photon contributes to the reduction of the PdCl ion by the one-photon process and to the autocatalytic growth of the Pd particles by the multi-photon process.

Micro-orientation control of silicon polymer thin films on graphite surfaces modified by heteroatom doping

Shimoyama, Iwao; Baba, Yuji; Hirao, Norie*

Advances in Engineering (Internet), 1 Pages, 2018/02

The performance of organic devices largely depends on molecular orientation in organic films. Whereas micro-orientation control of organic molecules is an indispensable technology for integration of organic devices, the method has not been established. We attempted to control micro-orientation of polydimethylsilane (PDMS) thin films by deposition of PDMS on graphite substrates modified by hetero atom doping using ion beam. Polarization dependence measurements of X-ray absorption spectroscopy and molecular orbital calculations clarified that PDMS films have lying, standing, and random orientations on the non irradiated, N-irradiated, and Ar-irradiated graphite surfaces, respectively. Furthermore, photoemission microscopy observation clarified that a PDMS film showed micro-patterns on a graphite surface with a microstructure on the order of m by separating N-irradiated and non irradiated areas. These results demonstrate our method is promising for micro-orientation of organic molecules.

Preferred site occupation of 3 atoms in NiFeN ( = 1 and 3) films revealed by X-ray absorption spectroscopy and magnetic circular dichroism

Takata, Fumiya*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Takanashi, Koki*; Kimura, Akio*; Suemasu, Takashi*

Physical Review Materials (Internet), 2(2), p.024407_1 - 024407_5, 2018/02

https://doi.org/10.1103/PhysRevMaterials.2.024407

Element specific electronic states and spin-flip-like behavior of Ce in (CeGd)Ni composed of heavy fermion CeNi and ferri-magnet GdNi through XMCD method

Yano, Kazuo*; Okane, Tetsuo; Takeda, Yukiharu; Yamagami, Hiroshi; Fujimori, Atsushi; Nishimura, Katsuhiko*; Sato, Kiyoo*

Physica B; Condensed Matter, 515, p.118 - 125, 2017/06

https://doi.org/10.1016/j.physb.2017.03.012

The electronic states of the three constituent elements in the crystal mixed system between CeNi and GdNi, CeGdNi, were investigated by soft X-ray magnetic circular dichroism (XMCD). Not only Gd 4f but also Ni 3d and Ce 4f electrons were magnetic and both magnetic moments of Ni and Ce were coupled anti-parallel to the direction of the Gd magnetic moment. After saturation, Ce magnetic moment decreased over 2 T and this behavior was explained by a spin-flip behavior of the Ce magnetic moment. In addition, sum rule analysis has revealed that the magnetic moments of Gd 4 f and Ni 3d electrons could retain small values of orbital magnetic moments.

Non-destructive depth analysis of the surface oxide layer on MgSi with XPS and XAS

Esaka, Fumitaka; Nojima, Takehiro; Udono, Haruhiko*; Magara, Masaaki; Yamamoto, Hiroyuki

Surface and Interface Analysis, 48(7), p.432 - 435, 2016/07

https://doi.org/10.1002/sia.5939

XPS is widely used for non-destructive chemical state analysis of solid materials. In this method, depth profiling can be carried out by a combination with ion beam sputtering. However, the sputtering often causes segregation and preferential sputtering of atoms and gives inaccurate information. The use of energy-tunable X-rays from synchrotron radiation (SR) enables us to perform non-destructive depth profiling in XPS. Here, the analytical depth can be changed by changing excitation X-ray energy. In the present study, we examined methods to perform depth profiling with XPS by changing excitation energy and XAS by changing electron energy for detection. These methods were then applied to the analysis of native surface oxide layers on MgSi crystals. In this XAS analysis, the peak at 1843.4 eV becomes dominant when the electron energy for detection increases, which implies that Si-O or Si-O-Mg structure is formed as the surface oxide layer on the MgSi.

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

https://doi.org/10.1080/15421406.2015.1096990

Organic electrically conducting -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.

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

https://doi.org/10.1080/15421406.2015.1105081

Unoccupied electronic states near the Fermi level of poly(dimethylsilane) were probed using Si 1s X-ray absorption spectroscopy (XAS) and Si KLL 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 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.