Comparative Study of Thickness Dependence of Critical Current Density of Yba₂Cu₃O_7–δ on (100) SrTiO₃ and on Rolling-assisted Biaxially Textured Substrates

We investigated the dependence of critical current density (J_c) on thickness of Yba₂Cu₃O_7−δ (YBCO) films grown by pulsed laser deposition on (100) SrTiO₃ (STO) and on rolling-assisted biaxially textured substrates (RABiTS). The thickness of YBCO films varied from 0.19 to 3 μm. The highest J_cs of 5.3 and 2.6 MA/cm² at 77 K, self-field were obtained for 0.19-μm YBCO films on STO and RABiTS, respectively. J_c was found to decrease exponentially with YBCO thickness on both substrates. However, the results suggest different mechanisms are responsible for the J_c reduction in the two cases. On STO, growth of a-axis grains within c-axis films and broadening of the in-plane texture were observed in thick films. On RABiTS, degradation in cube texture as well as development of a porous surface morphology were found to correlate with film thickness.