Superconductivity and cu valence of Bi-Sr-Ca-Cu-O thin films
S. Kohiki, K. Hirochi, H. Adachi, K. Setsune, K. Wasa
DOI 10.1103/PhysRevB.38.9201 · Physical Review B
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Abstract
Bi-Sr-Ca-Cu-O superconducting films were prepared by rf magnetron sputtering using a target with modulated composition and successive annealing in oxygen. The resistivity and Cu valence of the films varied before and after annealing. The zero-resistance temperature of the films was 10 K before the annealing, and rose up to 96 K (midpoint 105 K) after annealing. Essentially no change in the characteristic layer spacing (d value) of ≅ 18 Å, corresponding to c2, was observed before and after annealing as seen by x-ray diffraction. The Cu valence of the films was investigated by x-ray photoemission before and after annealing. The photoemission core-level spectra and LMM Auger emission spectra revealed that the Cu valence after annealing became larger than that obtained before annealing. The superconductivity obviously is correlated with the Cu valence of the films.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Bi-Sr-Ca-Cu2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 105 | Pressure not reported | unknown |
| Bi-Sr-Ca-Cu2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 70 | Pressure not reported | unknown |
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