Degradation of YBa₂Cu₃O_7—x Films under Transport Current

The effect of the current pulse bias on the electrical characteristics and surface morphology of YBCO films during the time 70 to 300 h at T = 78 K has been investigated. The YBCO films were deposited onto an Al₂O₃ (r-cut) substrate with CeO₂ buffer layer in situ by magnetron sputtering. Two types of experimental conditions have been used: the film under test was periodically switched to the resistive state by a low-frequency pulsed current; the film under test was in the superconducting state under a pulsed current with magnitude less than the critical one. Scanning electron microscopy has been used to characterize the surface morphology of the films. In the resistive state the surface morphology has been changed due to the formation of voids and hillocks. A few samples failed owing to discontinuities originated under the current. In the superconducting state damage of the samples was also observed. No change in the electrical characteristics of the survived samples was observed under both types of experimental conditions.