High-resolution electron microscopy investigations of stacking faults in Y1Ba2Cu3O7-delta metalorganic chemical vapor deposited thin films

New structural planar defects in Ba-deficient Y1Ba2Cu3O7-delta (YBCO) (1:1. 6:3) thin films grown on NdGaO3 and SrTiO3 substrates by metalorganic chemi cal vapor deposition have been observed by means of high-resolution electro n microscopy. The defects are associated with perturbations of the YBCO "1: 2:3" stacking sequences along the c direction which give rise to structural variants with locally "2:5:7," "3:4:7," or "4:6:10" cationic stoichiometri es. The defects can be consistently interpreted as CuO-YO-CuO/CuO conversio ns or YO/BaO (BaO/YO) interconversions in the (a,b) planes and extending ov er a few nanometers along the c axis. Structural models based on image matc hing with simulations are proposed for two particular cases. It is thought that these structural imperfections can be effective sites of flux pinning.