Raman Scattering Studies of YBa₂Cu₃O_7−x Films Grown by High-Rate e-Beam Co-Evaporation

We present results of Raman scattering studies of superconducting YBa₂Cu₃O_7-x (YBCO) films grown by a high-rate electron-beam co-evaporation method. It is shown by X-ray diffraction that the as-grown YBCO films have a highly c-axis oriented and in-plane aligned texture. Raman scattering measurements were used to study optical phonon modes, oxygen content and second phases of the YBCO coated conductors. Raman spectra of YBCO films with lower-transport properties exhibit additional phonon modes at ~ 300 cm^-1, ~ 600 cm^-1, and ~ 630 cm^-1, which are related to second-phases such as Ba₂Cu₃O_5.9 and BaCuO₂. We also performed micro-Raman scattering measurements, which enable the local characterization of the material over a few micrometer scales. We could clearly determine the chemical homogeneities of the films on which we could not have information using XRD. Our results strongly suggest that micro-Raman scattering can be a very effective tool for characterizing structural and chemical properties, which is essential for optimizing growth conditions.