In situ processing of epitaxial Y-Ba-Cu-O high T_c superconducting films on (100) SrTiO₃ and (100) YS-ZrO₂ substrates at 500-650 °C

We report the formation of excellent quality epitaxial YBa ₂Cu₃O₇ films on (100) SrTiO₃ and (100) ZrO₂ (yttria stabilized) substrates in the temperature range of 500-650°C by XECl excimer laser ablation in a 0.2 Torr oxygen ambient. By applying a dc bias voltage of +300 V to an interposing ring, we were able to reduce the substrate temperatures from 650 to 500°C for obtaining epitaxial films. The quality of the epitaxial films was found to decrease with temperature, particularly below 550°C. The thickness of the superconducting films was varied from 500 to 5000 Å with superconducting transition temperatures T_c (zero resistance) varying from 87 to 90 K for 650°C deposits. The critical current density J_c of films was found to vary linearly with temperature with values of (zero magnetic field at 77 K) 5.0×10⁶ and 1.0×10⁶ for films deposited at 650°C on (100) SrTiO₃ and (100) yttria-stabilized zirconia substrates, respectively. X-ray diffraction, transmission electron microscopy, electron channeling patterns, and Rutherford backscattering (RBS)/channeling showed excellent epitaxial quality of films on both substrates with best values of minimum ion channeling yield of 3.5% on (100) SrTiO₃ substrates.