Characterization of electronic structure of superconducting (Cu, C)–Ba–O films by in situ photoemission spectroscopy

Change of electronic structure of superconducting (Cu, C)-1201 thin films grown by pulsed laser deposition with superconducting critical temperature Tc has been characterized by means of in situ photoemission spectroscopy. The finite spectral weight at the Fermi level in the valence band of (Cu, C)-1201 superconducting thin films and a rigid-band-like approach of the main peak of the valence band toward the Fermi level with a rise of Tc has been observed, which reveals hole-doping-induced superconductivity of this system. The obtained Ba 4d and Cu 2p signals with an increase of Tc suggest excess oxygen should be introduced around Ba ions in the early stage of the emergence of superconductivity. Then, they should be preferentially introduced around Cu ions. The changes of core signals with Tc and comparisons of the obtained data with infinite-layer and other cuprate superconductor compounds suggest that the (Cu, C)–O charge reservoir in this system is in the heavily hole-doped state, similar to that of the Cu–O chain in YBa2Cu3O7−δ.

[1]  T. Makimōto,et al.  Thin film growth of (Cu, C)Ba2Ca(n−1)CunOy (n=1–4) superconductor by molecular beam epitaxy , 2007 .

[2]  Takafumi Ogata,et al.  Fabrication of (Cu, C)Ba2CuOy superconducting thin film by RF magnetron sputtering , 2006 .

[3]  T. Okuda,et al.  Pulsed Laser Deposition Synthesis and Photoemission Study of Superconducting Ba-Cu-O Thin Films , 2006 .

[4]  Y. Tanaka,et al.  Soliton in two-band superconductor. , 2001, Physical review letters.

[5]  N. Hamada,et al.  Electronic band structures of CuBa2Can−1CunO2n+2 and CuBa2Can−1CunO2n+1F (n=3–5) , 2001 .

[6]  S. Martellucci,et al.  Reflection high-energy electron diffraction oscillations during epitaxial growth of artificially layered films of (BaCuOx)m/(CaCuO2)n , 2000, cond-mat/0007432.

[7]  M. Tokumoto,et al.  High pressure synthesis and characterization of single crystals of CuBa2Ca3Cu4Oy superconductor , 1998 .

[8]  S. Ishibashi,et al.  In-situ characterization of doping-effect on electronic structure of epitaxial films of infinite layer SrCuO2 , 1996 .

[9]  T. Satoh,et al.  Incorporation of carbon into infinite-layer BaCuO2 films and formation of superconducting phase , 1995 .

[10]  B. Hunt,et al.  Valence band and Ba core level study of chemically-etched YBa2Cu3O7-δ , 1991 .

[11]  R. Vasquez,et al.  X-ray photoelectron spectroscopy study of chemically etched Tl2Ba2CaCu2O8+x thin film surfaces , 1991 .

[12]  R. Vasquez,et al.  Study of chemically-etched Bi2Sr2−xCa1+xCu2O8+δ surfaces , 1991 .

[13]  V. Kinsinger,et al.  The Cu valence in the highTc superconductors and in monovalent, divalent and trivalent copper oxides determined from XPS core level spectroscopy , 1987 .