Effect of structure and morphology on resistive loss at 10 GHz of the large-area laser-deposited YBa2Cu3O7 thin films

Abstract

Three large-area YBa2Cu3O7(YBCO) superconducting thin films have been laser-deposited under almost identical conditions. However, the microwave surface resistance Rs of the films deviated greatly, they are 280 μΩ, 3.78 mΩ, and 97 mΩ, respectively. It was found that the structure and morphology of the films greatly influence the resistive losses at 10 GHz and 77 K of the YBCO thin films. Different loss mechanisms were discussed. For high Rs, the large angle grain boundaries were the dominate defect in the thin films and increased the Rs of the film markedly. For low Rs, it was mainly due to the misaligned ‘‘123’’ grains in the thin films and the intrinsic loss. For Rs up to the mΩ range, besides the misaligned 123 grains, domain boundaries and nonsuperconducting outgrowths of different sizes appeared and this caused the rise of Rs value. All these results were given experimentally and discussed theoretically.