Strain analysis and structural characterization of SrCuO2/CaCuO2 infinite layer superlattices

A detailed structural characterization of SrCuO2/CaCuO2 infinite layer superlattices is presented. The analyses are performed by using high-resolution X-ray diffraction, reciprocal space mapping and X-ray specular reflectivity. In addition, preliminary results of X-ray photoelectron spectroscopy are reported, The X-ray analyses confirm the high structural quality of infinite layer superlattices deposited by pulsed laser technique on slightly misoriented SrTiO3 substrates. The strain analyses indicate that (i) a macroscopic tilt of the superlattice with respect to the substrate lattice occurs, and (ii) the SrCuO2 layers are in a relaxed state, while the CaCuO2 unit cells are tetragonally distorted with respect the SrCuO2 lattice. The low-angle X-ray measurements reveal good interfacial properties and indicate a partial correlation of the interface roughness across the layers. A computer simulation of the experimental X-ray specular reflectivity patterns yields an average interface roughness of about 4 Angstrom. Finally, the X-ray photoelectron spectroscopy investigations confirm the good quality of the infinite layer superlattices with a correct stoichiometric contents and, particularly, a chemical state of CuO2 planes similar to that of typical high quality superconducting YBCO thin films.