Raman Scattering Studies of ${rm YBa}_{2}{rm Cu}_{3}{rm O}_{7-{rm x}}$ Films Grown by High-Rate e-Beam Co-Evaporation

摘要

We present results of Raman scattering studies of superconducting ${rm YBa}_{2}{rm Cu}_{3}{rm O}_{7-{rm x}}$ (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 $sim 300 {rm cm}^{-1}$, $sim 600 {rm cm}^{-1}$, and $sim 630 {rm cm}^{-1}$, which are related to second-phases such as ${rm Ba}_{2}{rm Cu}_{3}{rm O}_{5.9}$ and ${rm BaCuO}_{2}$ . 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.