Process monitoring during post-annealing of YBa2Cu3O7 thin films containing fluorine

The post-annealing method of producing thin films of YBa₂Cu₃O₇ (YBCO) has taken on a new impetus due to the recent work showing that films of the highest quality can be made by using low partial pressures of oxygen during the annealing cycle. Here it is shown that for films produced by using BaF₂ as a source material, the post-annealing procedure can be closely controlled by monitoring the F that evolves due to the water vapor reaction with BaF₂. The use of an ion-sensitive electrode allowed small F evolution rates (about 1 ng s^?1) to be detected above background, sufficient to measure the F evolution rate from even the smallest samples used. The time interval during which F evolves was found to increase with increasing YBCO film area being annealed.