Friday, 2D-16, 5:40-5:50

Raman Scattering Spectroscopy and Phase Stability of Rare-earth based Cuprate Thin Tilms for Coated Conductor Applications

W. Jo

G. Kim¹, G. M. Shin², and S. I. Yoo²

¹Department of Physics, Ewha Womans University, Seoul 120-750, Korea
²School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea

We analyzed Gd_1+xBa _2−xCu₃O₇ (GdBCO) thin films by using Raman scattering spectroscopy. Highly oriented GdBCO films were deposited on ion beam assisted deposition MgO templates by pulsed laser deposition. We used thin LaMnO₃ buffer layers between MgO layers and superconducting GdBCO films by pulsed laser deposition. X-ray diffraction studies show highly oriented c-axis in-plane orientation as well as out-of plane textures less than 7 degree. Polarization dependent Raman scattering spectroscopy shows that the GdBCO film contains preferentially c-axis oriented grains and little cation disorder between Gd³⁺ ions and Ba²⁺ sites, which is very different from the case of Nd-based cuprates. Growth temperature and oxygen partial pressure of the GdBCO films is carefully compared with the known phase stability lines. The stoichimetric and well-ordered GdBCO films exhibit a high critical current (I_c) of 90 ~ 100 Acm at 77 K and self-field. From the Raman spectra, the O(2)-O(3) vibration and the O(4) vibration were found at 328 and 448 cm^-1, respectively. In particular, apical oxygen is well characterized around 500 ~ 505 cm^-1, which is known to be important for high T_c and J_c in rare-earth based cuprates. We could not observe any Ba-Cu oxide peaks, indicating that our process conditions are not liquid-based, which is a possible route to increase growth rates.

This work has been supported by the "Center for Applied Superconductivity Technology" under "21st Century Frontier R&D Programs" of the Ministry of Science and Technology.

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