Surface resistance of Bi-2212 films and influence of intergrowth

We investigated surface resistance R-s of Bi-2212-based films fabricated by the multitarget sputtering technique, focusing on the effect of intergrowt h on R-s. The Bi-2212 single-phase film had surface resistance R-s of about 1 m Omega at 30 K and 20 GHz. Intergrowth with Bi-2201 made the R-s worse, while intergrowth with Bi-2223 improved, not only the R-s, but also the cr itical current density J(c) more than expected from the ratio of Bi-2223. T hese phenomena were discussed in terms of the change in the carrier density by the intergrowth. The improvement of these properties by the intergrowth with Bi-2223 was possibly due to the decrease in carrier density in Bi-221 2, which is naturally overdoped, by the interaction with neighboring Bi-222 3 cells. (C) 2000 Elsevier Science B.V. All rights reserved.