Superconducting NdBa₂Cu₃O_7-δ thin films grown on bare (11̄02) sapphire by pulsed laser deposition

Superconducting NdBa₂ Cu₃ O_7-δ (NBCO) thin films with T_c=89 K have been successfully grown on bare (11 02) sapphire substrates by pulsed laser deposition (PLD). The X-ray diffraction results show that the as-grown NBCO films are all c-axis oriented with no observable second phase. The c-axis parameter decreases monotonically with increasing the deposition temperature (T_s), suggesting that the corresponding degradation of T_c for T_s> 790 °C might not originate from oxygen deficiency. It is conceived that the film-substrate reaction that occurring at the interface may cause Ba-deficiency and hence enhance Nd-Ba antisite substitutions.