In situ growth and flux pinning in Ag-doped YBa2Cu3O7-y thin films

We have grown in situ Ag-doped YBa2Cu3O7-y thin films by high-pressure magnetron sputtering using a stoichiometric target. The sputtering was carried out in a mixture of Ar (70%) and O2 (30%) at a pressure of 200 mTorr, with the substrate temperature kept at about 700°C during sputtering. We made a relatively high-pressure oxygen environment by employing an oxygen jet near the substrates. After deposition one atmosphere of O2 was introduced into the chamber, and the sample was cooled down to room temperature slowly (5°C/min). This method gives highly reproducible superconducting films with Tc (50%) at 8388 K and zero resistance at 7887 K depending on the growth conditions and the substrates used. In magnetic fields there is a narrowing of the resistive transition width for Y-Ba-Cu-O films with Ag impurities. We attribute the narrowing to the enhanced flux pinning due to the Ag impurities.