As-grown Y-Ba-Cu-O thin films by reactive coevaporation with oxygen plasma cooling

Abstract
We have developed a new fabrication process of as‐grown Y‐Ba‐Cu‐O thin films using a reactive coevaporation method specially with the rf‐plasma cooling in the low oxygen pressure of 0.4 mTorr. By this O2 plasma cooling process, the transition temperature Tc is improved from 40 to 81 K for the film with a thickness of 1000 Å. The x‐ray diffraction analysis shows that the activated oxygen species generated by the rf plasma make Y‐Ba‐Cu‐O films oxidize sufficiently even in the low pressure of oxygen. In addition, we have studied the thickness dependence of Tc for as‐grown films with various thicknesses of 60–2000 Å.