Reactive coevaporation of YBaCuO superconducting films

The conditions for the preparation of a superconducting YBaCuO thin films by in situ reactive coevaporation are described. These films, in the best cases, are superconducting with Tc up to 90 K and Jc (at 4.2 K) above 10 to the 7th A/sq cm. It was found that, for the growth of superconducting thin films, the minimum required partial oxygen pressure of 1 mtorr was needed, and that, at low oxygen pressure, films with average compositions off the 1-2-3 stoichiometry had higher Tc. Results indicate that cation disorder may become increasingly important at reduced oxygen pressure. It is suggested that cation disorder may be favorable for some superconducting properties, such as critical currents, while not significantly affecting other properties.