MICROSTRUCTURE OF HIGH-TEMPERATURE SUPERCONDUCTOR THIN-FILMS AS STUDIED BY MICRO-RAMAN SPECTROSCOPY

Based on correlations established between Raman spectra and structure and on high anisotropy in Raman polarization of superconducting materials, the micro-structure and orientation of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O thin films deposited on various substrates were determined for both surfaces having grains or without grain. A relationship, established between the Cu2-O1 vibrational frequency vH (467-503 cm-1) and the oxygen content x in YBa2Cu3O(x): x = 0.025 vH - 5.57 facilitated a rapid evaluation of the oxygen content of any surface, by this non destructive technique. With step-etched surfaces, the micro-structure and epitaxial quality can be observed in function of the thickness of the deposit. Finally, with bevelled samples, micro-Raman spectroscopic technique also allows to illuminate a bilayer from the substrate to the interface then to the outer surface and can eventually show structural modifications or the appearance of new chemicals due to the interaction between the superconducting layer and the substrate.