Effect of deposition conditions on YBa2Cu3O 7-δ thin films by inverted cylindrical magnetron sputtering and substrate effects
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The dependence of YBCO thin film properties on the deposition conditions was studied for different substrates. The deposition conditions were optimized for the epitaxial growth of high quality YBCO thin films of 1500 Å thickness onto single crystal (100-oriented) SrTiO3 (STO), MgO and LaAlO3 (LAO) substrates by DC Inverted Cylindrical Magnetron Sputtering (ICMS). The samples were investigated in detail by means of X-ray diffraction analysis (XRD), EDX, AFM, ρ-T, magnetic susceptibility and current-voltage (I-V) characterizations. The samples show strong diamagnetic behavior and sharp transition temperatures of 89-91 K with ΔT < 0.5 K. XRD of the samples exhibited highly c-axis orientation. The full width at half maximum (FWHM) values of the rocking curves were ranging typically from 0.22 to 0.28°. The samples have smooth surfaces as shown from AFM micrographs. The surface roughness, Ra, changed between 5-7 nm. I-V characteristics were obtained from the 20μm-wide microbridges, which were patterned by a laser writing technique. The critical current densities (Jc, 1.06 × 106 for LAO-based YBCO, 1.39 × 106 for MgO-based YBCO, 1.67 × 106A/cm2 for STO based YBCO) of the microbridges were evaluated from I-V curves at 77 K.