Structural characterization of ultrathin cuprate artificial superconducting structures by x-ray synchrotron radiation

Grazing incidence x-ray diffraction and reflectivity measurements were carried out on ultrathin (a few unit cells thick) superconducting heterostructures, based on Ba0.9Nd0.1CuO2+x and CaCuO2 individual blocks, using undulator radiation from a third-generation synchrotron. We investigated films with different thicknesses of the intermediate CaCuO2 block, grown on (001)SrTiO3 substrates by the pulsed-laser deposition technique with no in situ diagnostic. In this communication we demonstrate that the thickness of such heterostructures can be controlled at the single unit cell level. This analysis shows that the interfaces between the different constituent blocks are very sharp with roughness less than one unit cell.