Superstructure in thin films of bi-based compounds on mgo

In situ epitaxial growth of BiSrCaCuO films by three target sputtering was performed on MgO substrates at a temperature of 650°C. From high resolution transmission electron microscopy, the film showed a superstructure consisting of the alternate stacking of the low-T_c and high-T_c phases with a c-axis of 34 A. The film in the [110] or [11̄0] directions was parallel to <100>MgO, and the transient layers between the substrate and the film were less than a few atomic layers thick. X-ray diffraction simulations indicated that the films contained random layer ordering of 34 A bi-layers (low-T_c + high-T_c and high-T_c + low-T_c) and random layer ordering of low-T_c and high-T_c phase layers.