Microstructure of superconducting copper oxycarbonate thin films of the Ba–Ca–Cu–C–O system

The microstructural state of a-axis-oriented superconducting oxycarbonate films, grown by pulsed laser ablation, has been studied by high resolution electron microscopy (HREM). The member m= 3 of the structural family (CaCuO2)m(Ba2CuO2CO3)n is preferentially stabilized, in agreement with the nominal composition of the target, but m′ members ranging between m′= 1 and 11 have been identified. Different types of domain boundaries, mainly parallel to {100}p or {110}p, involve local distortions of the framework. These non-stoichiometry features were analysed, and were found to involve complex structural mechanisms such as variations of the cationic distribution within the different types of layers, intergrowths perpendicular to the layers, and intercalations of [CaCu2O3] and [Ca2CuO3]-type layers.