EFFECTS OF OXYGEN-PRESSURE AND SUBSTRATE-TEMPERATURE ON THE INSITU GROWN BISRCACUO FILMS BY LASER ABLATION

The dependence of the phase formation on the oxygen pressures ranging from 2.0 X 10(-2) to 20 Torr and the substrate temperatures ranging from 500 to 750-degrees-C in the in situ grown BiSrCaCuO (BSCCO) films prepared by laser ablation from a Bi1.5Pb0.5Sr2Ca3Cu4Ox target was presented. The crystallization of significant amounts of the Bi2Sr2CaCu2Ox (2212) and Bi2Sr2CuOx (2201) phases appeared at 510-degrees-C. The minimum oxygen pressure required for the formation of the 2212 phase was 2.0 X 10(-2) Torr. Higher oxygen pressure enhanced the nucleation and growth of the 2201 phase and shifted the formation temperatures of the 2212 and Bi2Sr2Ca2Cu3Ox (2223) phases to be higher. The decomposition temperature of the perovskite structure increased with increasing the oxygen pressure. In this study, nearly pure 2212, 2223, and Bi2Sr2Ca3Cu4Ox (2234) films with the corresponding T(c) (zero) of 73, 83, and 71 K were, respectively, grown by varying the oxygen pressure and substrate temperature. The oxygen pressure and substrate temperature also played important roles in determining the microstructures and hence the superconductivity in the in situ grown BSCCO films. Conditions required for the successful in situ growth of the BSCCO films are prone to the higher oxygen pressure and lower substrate temperature in comparison with those of the YBa2Cu3Ox (123) films.