Journal of Synchrotron Radiation

Volume 13, Part 4 (July 2006)

research papers

J. Synchrotron Rad. (2006). 13, 314-320 [ doi:10.1107/S0909049506015251 ]

Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature superconducting thin-film single crystals

H. Oyanagi, A. Tsukada, M. Naito, N. L. Saini, M.-O. Lampert, D. Gutknecht, P. Dressler, S. Ogawa, K. Kasai, S. Mohamed and A. Fukano

Abstract: A Ge pixel array detector with 100 segments was applied to fluorescence X-ray absorption spectroscopy, probing the local structure of high-temperature superconducting thin-film single crystals (100 nm in thickness). Independent monitoring of pixel signals allows real-time inspection of artifacts owing to substrate diffractions. By optimizing the grazing-incidence angle [theta] and adjusting the azimuthal angle [varphi] , smooth extended X-ray absorption fine structure (EXAFS) oscillations were obtained for strained (La,Sr)₂CuO₄ thin-film single crystals grown by molecular beam epitaxy. The results of EXAFS data analysis show that the local structure (CuO₆ octahedron) in (La,Sr)₂CuO₄ thin films grown on LaSrAlO₄ and SrTiO₃ substrates is uniaxially distorted changing the tetragonality by 5 × 10^-3 in accordance with the crystallographic lattice mismatch. It is demonstrated that the local structure of thin-film single crystals can be probed with high accuracy at low temperature without interference from substrates.

Keywords: pixel array detector; fluorescence XAS; high-temperature superconductivity; thin-film single crystals.