Ba–Ca–Cu oxycarbonate thin films, prepared by pulsed laser deposition: structure, growth mechanism and superconducting properties

Abstract

Ba–Ca–Cu oxycarbonate superconducting thin films on LaAlO 3 (100) substrates were grown by pulsed laser deposition in off axis geometry. X-ray diffraction, selected area electron diffraction, and high-resolution transmission electron microscopy indicated that the films consisted of different phases of the (C x Cu 1− x )Ba 2Ca n−1 Cu n O 2 n+3 compound. The main phase was the n=4 phase (C x Cu 1− x )Ba 2Ca 3Cu 4O 11, besides other phases as the n=1,2,3,5… phases and precipitates of CaO. The films were grown predominantly a-axis oriented and contained, in a small amount, c-axis oriented domains of the n=4 phase near the film surface. An onset of superconductivity at 115 K and critical temperatures up to 78 K were found by AC resistive and inductive measurements.