Superconducting Y-Ba-Cu-O films have been prepared by on-axis DC magnetron sputtering from single sintered targets with various compositions, and relationships of transition temperature
Tc to film composition and
c-axis lattice parameter
c0 have been examined. Films with zero-resistance transition temperature
Tc, end exceeding 85K are easily obtained using Ba-poorer targets than stoichiometry under the conditions of lower oxygen pressures, 3-10mTorr, than those reported by other investigators. The
Tc and
c0 of these films strongly depend on X-ray intensity ratio Cu/Ba which has been obtained directly by EDX and is related to film composition ratio. As the Cu/Ba ratio is decreased from an optimum value,
Tc values rapidly decrease and
c0 values increases. Moreover, the
c0 values are influenced by X-ray intensity ratio Ba/Y. Although some films with higher Ba/Y ratios have
c0 values larger than 11.82Å (=tetragonal lattice parameter of bulk), they still show superconductivity. Their dependence of
Tc on
c0 is clearly different from that usually reported for bulk samples and post-annealed films. On the basis of these results, effects of oxygen pressure during sputter-deposition on
Tc, film composition and
c0 are discussed.
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