The interfaces in YBa2Cu3O7/BaTbO3and PrBa2Cu3O7/BaTbO3heterostructure thin films

Abstract

The interfaces in YBa 2 Cu 3 O 7 /BaTbO 3 and PrBa 2 Cu 3 O 7 /BaTbO 3 heterostructure thin films are investigated by high-resolution transmission electron microscopy. Depending on the deposition temperature of the BaTbO 3 layers two types of interface, type I and type II, are found. For a deposition temperature of 780°C the interfaces between YBa 2 Cu 3 O 7 and BaTbO 3 are of type I. In this configuration a Cu-O chain plane of YBa 2 Cu 3 O 7 or PrBa 2 Cu 3 O 7 faces a TbO 2 plane of BaTbO 3 . Interface dislocations are found whose line direction is [110] or [110]. Residual misfit can be observed in a layer close to the interface. At a deposition temperature of 500°C, type I and type II interfaces coexist. In the type II configuration, a Cu-O plane of YBa 2 Cu 3 O 7 or PrBa 2 Cu 3 O 7 faces a BaO plane of the BaTbO 3 layer. In this case, misfit dislocations are found to lie along the [100] and [010] directions. In addition close to the interface the lattice is strongly distorted. Models for the interface structure are suggested and tested by image simulation. The differences in dislocation configuration and residual strain level for the two types of interface are discussed in the light of O-lattice theory and the bonding state of the ions in the interface layer.