Superstructure in Thin Films of Bi-Based Compounds on MgO

Abstract

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 Å. The film in the [110] or [1 1̄0] 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 Å 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.