THIN-FILM YBA2CU3O7-X DIRECT-CURRENT SQUIDS WITH JOSEPHSON-JUNCTIONS MADE BY DIRECT ELECTRON-BEAM WRITING

We have investigated dc superconducting quantum interference devices ( SQUIDs) with loop areas 8 and 64 mu m(2) made by direct electron beam writing in YBa2Cu3O7-x films with thickness 25 and 50 nm. The SQUIDs h ave maximum peak-to-peak voltage modulation of about 20 mu V, which co rresponds to the transfer factor dV/d Phi(0) similar to 50-60 mu V/Phi (0) at 30-40 K. By measuring the mutual inductance of the SQUID signal line as a function of temperature and comparing the data with the num erical calculations and the two-fluid model, we extracted the values o f the London penetration depth for YBa2Cu3O7-x thin films. (C) 1996 Am erican Institute of Physics.