LOW-NOISE DC SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES IN BI2SR2CACU2O8+X THIN-FILMS

Low-noise dc superconducting quantum interference devices (SQUIDs) were fabricated by thin film deposition of Bi2Sr2Ca Cu 2O8+x (BSCCO) on bicrystalline substrates of SrTiO 3 with misorientation angles Θ from 24°to 45°. An optimized dc SQUID design (βL=1) was developed for Θ=24°. Therein the SQUID inductance was varied between 7 and 80 pH. Fabricated dc SQUIDs operated at 77 K as well as high-quality YBa 2Cu3O7-y (YBCO) SQUIDs, especially the 1/f and white noise levels were in the lowest range of data reported so far for YBCO SQUIDs and are two orders of magnitude better than noise data published this far for BSCCO SQUIDs at 77 K. © 1995 American Institute of Physics.