Soft x-ray spectroscopy of Ca-doped BiCuOSe thin films grown by pulsed laser deposition

ORAL

Abstract

Thin films of Ca-doped BiCuOSe were grown on (001) MgO and SrTiO$_{3}$ substrates via pulsed laser deposition. X-ray absorption and emission spectroscopy were used to analyze the O $K$-edge and Cu $L_{3,2}$-edge in order to determine the bulk electronic structure of BiCuOSe. Analysis of the O $K$-edge XAS/XES spectra yield a band gap of $\sim $1 eV, consistent with optical measurements on thin films. Optical measurements on single crystals show a band gap of $\sim $0.83 eV. XAS/XES results show the presence of strongly hybridized Bi 6$s$ - O 2$p$ orbitals in undoped samples. This hybridization is diminished in doped samples, providing strong evidence of Ca$^{2+}$ on the Bi$^{3+}$ site. X-ray diffraction measurements show that the films are highly oriented, with rocking curves around the (003) peak having a FWHM of 1\r{ }. Expansion of the c-axis is observed as Ca concentration is increased. All films show $p$-type conductivity and develop more metallic character as calcium doping increased. Ca concentration was determined by EPMA, which shows non-stoichiometric transfer of Ca from the target into the films.

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Authors

  • Jason Francis

    Physics Department, Oregon State University

  • A. Knecht

    Oregon State University, University of Idaho, Department of Chemistry, Oregon State University, Corvallis, OR, School of EECS, Oregon State University, Corvallis, OR, National Renewable Energy Laboratory, Golden, CO, Oregon Health and Science University, Linfield College, Purdue University, National Institute of Standards and Technology, Montana State University, University of British Columbia, University of Washington, Cornell University, Philipps-University, 35032 Marburg, Germany, University of Arizona, Tucson, Arizona 85721, Oregon State University, Corvallis, OR 97331, Physics Department, SUNY Binghamton, Physics Department, Oregon State University, Argonne National Laboratory

  • A. Knecht

    Oregon State University, University of Idaho, Department of Chemistry, Oregon State University, Corvallis, OR, School of EECS, Oregon State University, Corvallis, OR, National Renewable Energy Laboratory, Golden, CO, Oregon Health and Science University, Linfield College, Purdue University, National Institute of Standards and Technology, Montana State University, University of British Columbia, University of Washington, Cornell University, Philipps-University, 35032 Marburg, Germany, University of Arizona, Tucson, Arizona 85721, Oregon State University, Corvallis, OR 97331, Physics Department, SUNY Binghamton, Physics Department, Oregon State University, Argonne National Laboratory

  • A. Knecht

    Oregon State University, University of Idaho, Department of Chemistry, Oregon State University, Corvallis, OR, School of EECS, Oregon State University, Corvallis, OR, National Renewable Energy Laboratory, Golden, CO, Oregon Health and Science University, Linfield College, Purdue University, National Institute of Standards and Technology, Montana State University, University of British Columbia, University of Washington, Cornell University, Philipps-University, 35032 Marburg, Germany, University of Arizona, Tucson, Arizona 85721, Oregon State University, Corvallis, OR 97331, Physics Department, SUNY Binghamton, Physics Department, Oregon State University, Argonne National Laboratory