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Ikeura, Hiromi*; Sekiguchi, Tetsuhiro
Japanese Journal of Applied Physics, 58(SI), p.SIIC04_1 - SIIC04_4, 2019/08
Times Cited Count：0 Percentile：0(Physics, Applied)The electronic structure of the unoccupied conduction band of polycrystalline chloroaluminum phthalocyanine was investigated by X-ray absorption spectroscopy (XAS) near the Cl K-edge. XAS spectra were recorded in total electron yield (TEY) and partial Auger electron yield (AEY) modes. Partial AEY spectra were measured using normal and spectator Cl KL
L Auger yields as a function of photon energy. Although the TEY spectrum showed a broad shape; that was difficult to deconvolute curve fitting, the normal and spectator AEY spectra clearly showed that 
*(Cl-Al) transition splits into two competitive peaks attributed to the core excitons (localized with a core hole) and conduction band (delocalized without a core hole). The existence of a band-like peak in the Cl K-edge XAS is evidence that the Cl axial ligand participates in forming the conduction band. Thus, band-like electron transport is expected to occur in the oligomer-like (-Al-Cl-Al-) site.
Ikeura, Hiromi*; Sekiguchi, Tetsuhiro
Molecular Crystals and Liquid Crystals, 622(1), p.50 - 54, 2015/12
Times Cited Count：0 Percentile：0.01(Chemistry, Multidisciplinary)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.
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 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.
and O ion-implanted Si(100)Yamamoto, Hiroyuki; Baba, Yuji; Sasaki, Teikichi
Surface and Interface Analysis, 23, p.381 - 385, 1995/00
Times Cited Count：17 Percentile：53.88(Chemistry, Physical)no abstracts in English
Ikeura, Hiromi*; Sekiguchi, Tetsuhiro
no journal, ,
Femo and atto second electron dynamics through unoccupied conduction band in organic electronic materials can be probed by Auger spectroscopy (RAS). In this method, RAS spectra are interpreted based on two competing decay channels: core-hole decay and core-excited resonant electron delocalization. Recent progress in our understanding of previous data, we found that maximum energies in P K-edge X-ray absorption spectra (XAS) measured by Auger electron yields are different between spectator Auger (SA) and normal Auger (NA) for phosphate groups in DNA and nucleotides. This can be explained by core excitation binding energy shifts for the localized state corresponding to SA.
