Percolation behaviour in intergrowth BiSrCaCuO structures grown by molecular beam epitaxy

BiSrCaCuO thin films and specially Bi-2212 compounds were grown on (100) SrTiO 3 substrates by molecular beam epitaxy (MBE). The growth mechanism was controlled in real time by monitoring the RHEED intensity. The deposition sequence of the elements was also varied in order to induce intergrowth structures at nanometer scale. The resulting high density of stacking faults is in contrast with a very low roughness (in the range of 1 nm as measured by atomic force microscopy), a strong c-axis texturation, and a full epitaxy within the ab-plane as confirmed by four circle X-ray diffraction. The local structure of the films was examined by high resolution transmission electron microscopy (HRTEM) in correlation with the superconducting properties. Both structural and transport properties seem to be deeply affected by the percolation of 2212 domains as their concentration in the film is changed.