Bayesian sparse modeling of extended x-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film
Hiroyuki Kumazoe,
Yasuhiko Igarashi,
Fabio Iesari,
Ryota Shimizu,
Yuya Komatsu,
Taro Hitosugi,
Daiju Matsumura,
Hiroyuki Saitoh,
Kazunori Iwamitsu,
Toshihiro Okajima,
Yoshiki Seno,
Masato Okada,
Ichiro Akai
Affiliations
Hiroyuki Kumazoe
Institute of Industrial Nanomaterials, Kumamoto University, Kumamoto 860-8555, Japan
Yasuhiko Igarashi
Faculty of Engineering, Information and Systems, University of Tsukuba, Tsukuba 305-8573, Japan
Fabio Iesari
Aichi Synchrotron Radiation Center, Aichi 489-0965, Japan
Ryota Shimizu
Japan Science and Technology Agency, PRESTO, Saitama 332-0012, Japan
Yuya Komatsu
School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
Taro Hitosugi
School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
Daiju Matsumura
Materials Sciences Research Center, Japan Atomic Energy Agency, Hyogo 679-5148, Japan
Hiroyuki Saitoh
Quantum Beam Science Research Directorate, National Institute for Quantum Science and Technology, Hyogo 679-5148, Japan
Kazunori Iwamitsu
Technical Division, Kumamoto University, Kumamoto 860-8555, Japan
Toshihiro Okajima
Aichi Synchrotron Radiation Center, Aichi 489-0965, Japan
Yoshiki Seno
Kyushu Synchrotron Light Research Center, Saga 841-0005, Japan
Masato Okada
Department of Complexity Science and Engineering, The University of Tokyo, Chiba 277-8561, Japan
Ichiro Akai
Institute of Industrial Nanomaterials, Kumamoto University, Kumamoto 860-8555, Japan
This article presents a Bayesian sparse modeling method to analyze extended x-ray absorption fine structure (EXAFS) data with basis functions built on two-body signals. This method does not require any structural model and allows us to evaluate regression coefficients proportional to the radial distribution functions of the respective elements and their errors and is very effective for analysis of EXAFS with weak absorption intensity and severe signal-to-noise ratios. As an application example, we used it to analyze the EXAFS of an yttrium oxyhydride (YOxHy) epitaxial thin film. These EXAFS data show weak absorption intensity and a severe signal-to-noise ratio due to the small amount of x-ray absorption in the thin film sample. However, this approach revealed that the radial distance ratio of the second neighbor yttrium to the first neighbor oxygen coincides with that of a tetrahedral configuration. This result demonstrates that the interstitial oxygen position is tetrahedral in the YOxHy thin film.
