GROWTH OF (PB0.75CU0.25)SR2(Y1-YCAY)CU2O7 THIN-FILMS BY LASER ABLATION

In this letter we investigate the effects of varying the values of x and y in (Pb1-xCux)Sr2(Y1-yCay)Cu2O7 films deposited by laser ablation. The films are grown in situ on (100) LaAlO3 at the relatively low substrate temperature of 620-degrees-C. The films are highly oriented with the c-axis perpendicular to the substrate and exhibit a surface morphology which is unique to the oxide superconductors. By substituting Ca for Y it is possible to systematically vary the superconducting transition temperature from 10 K to a maximum of 86 K. On the other hand, variations in the value of x seem to suggest that the film's copper concentration in the (PbCu) plane can only exist within the narrow range of approximately x = 0.2-0.3 and any extra copper added to the target ends up in an impurity phase.