CHINESE JOURNAL OF PHYSICS VOL. 38, NO. 2-II APRIL 2000

Polarization-Dependent X-ray Absorption Spectroscopy of La₂CuO₄F_x Thin Films Using Synchrotron Radiation

J. M. Chen¹, P. Nachimuthu¹, R. S. Liu², and P. P. Edwards<sup>3

1</sup>Synchrotron Radiation Research Center (SRRC), Hsinchu, Taiwan 300, R.O.C.

²Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, R.O.C.

³School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K.
(Received August 17, 1999)

High-resolution polarization-dependent O K-edge x-ray absorption spectra for c-axis oriented La₂CuO₄F_x thin films were investigated. In the O 1s absorption edge of La₂CuO₄F_x, the prepeak at 528.7 eV is assigned to transitions into O 2p_xy hole states located in the CuO₂ planes. Fluoride ions present in La₂CuO₄F_x induce hole states in the CuO₂ planes near the Fermi level, which in turn play an important role in enhancing superconductivity for this compound, as compared to parent La₂CuO₄. In La₂CuO₄F_x, fluoride ions are regarded as an electronic dopant to induce superconductivity.

PACS. 74.25.Jb - Electronic structure.

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