Structure refinement of Ba-based infinite-layer superlattices

The structure of BaCuO(2) and CaCuO(2) thin crystalline films and of artificially layered (BaCuO(2))(2)/(CaCuO(2))(2) superconducting superlattices, obtained by the pulsed laser deposition technique, is investigated by x-ray diffractometry and electron microprobe. Simulations of x-ray diffraction and x-ray specular reflectivity data piloted by stoichiometric data obtained from microanalytical measurements lead to an accurate structure refinement of the investigated films. We found that the BaCuO(2) compound can be deposited in the infinite layer phase, even if the real structure can present many percents of copper vacancies in the CuO(2) planes. Also in the (BaCuO(2))(2) layers of the investigated superconducting superlattices the Cu/Ba ratio obtained by the simulations is less than one. However, in this latter case the copper vacancies are localized only in the CuO(2), planes between barium atoms. Nonstoichiometric compounds with an excess of oxygen are compatible with the experimental data, indicating the Ba(2)Cu(2-x)O(4-y), layers as the "reservoir charge blocks" in the superconducting superlattices.