DEFECT FORMATION CAUSED BY A TRANSIENT DECREASE IN THE AMBIENT OXYGEN CONCENTRATION DURING GROWTH OF YBA2CU3O7-DELTA FILMS

Thin films of YBa2Cu3O7-δ have been grown in an oxygen atmosphere by pulsed laser deposition using two synchronized lasers, separated by a variable delay (1 μs-10 ms). The ablated fragments from the first laser lead to formation of a blast wave in O2, leaving behind a rarefied ambient. If the second laser is triggered before the O 2 pressure returns to equilibrium, the resulting films show a decrease in transition temperature with an expanded c-lattice parameter caused by defects in the nonchain sites of YBa2Cu3O 7-δ. This demonstrates the necessity of maintaining a sufficiently high concentration of oxygen within the time period that the fragments travel and deposit on the substrate.