Optimization of Jc for Photo-Assisted MOCVD Prepared YBCO Thin Films by Robust Design

Abstract

Metalorganic chemical vapor deposition (MOCVD) is emerging as a practical high T_c superconducting thin film preparation technique for industrial application. Intrinsically this technique involves a large number of variable parameters. This is especially critical for the quarternary or higher high T_c materials. Thus, effective methods are required to optimize the parameters for the preparation of high T_c films. A matrix experimental design named Robust Design has been employed for this purpose. The first-phase design was based on a starting knowledge of growth temperature and pressure, and annealing temperature for MOCVD preparation of YBCO thin films. A minimum lab effort of only nine deposition experiments was then used to optimize the process control parameters of precursor oven temperature, carrier gas (Ar) flow rate, O₂ flow rate and N₂O flow rate. The results were then followed by three confirmation depositions. The Robust Design resulted in the growth of YBCO film with Tc consistently in the range of 87.0 K to 90.2 K and Jc improved from about 1.0 × 10⁶ A/cm² to 3-5 × 10⁶ A/cm².