Correlation between structural disorder and electric properties in YBa2Cu3O7-δ (YBCO)

The degradation of the surface resistance Rs of YBCO material by ion milling is usually supposed to be linked to oxygen loss and crystallographic defects. To study this effect, the structural and physical analysis of the milled YBCO thin film has been carried out using Ion Beam Analyses and SQUID measurements. The cationic composition and the oxygen quantity measured in the disordered layer on the top of the film are the same on milled and reference samples. An increase of the bulk defect concentration, especially in the oxygen sublattice, is observed in the layer underlying the disordered layer. From SQUID measurements, the milled sample shows a degradation of susceptibility vs temperature X(T) compared to the reference sample. This observation is in a good agreement with the structural analysis and the Rs measurements. After an oxygen annealing at 450deg. C on the milled samples, the cationic disorder decreased and the bulk defect concentration has not been affected. The X(T) characteristic has improved for the milled film showing its correlation with the evolution of the disordered layer. However the Rs value of the annealed material is not restored