Improvement of IBAD MgO template layers on metallic substrates for YBCO HTS deposition

Abstract

We present our results to improve ion beam assisted deposition (IBAD) of magnesia (MgO) templates for subsequent YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) deposition. The substrate surface roughness has a significant effect on the initial nucleation texture of IBAD MgO films. We have found that reduction in our substrate surface roughness to /spl sim/ 3.5 nm has resulted in better in-plane texture for IBAD MgO films than those deposited on rougher metal substrates. We have further improved the IBAD MgO deposition parameters by using an in situ reflected high-energy electron diffraction (RHEED) analysis tool that allows for monitoring of IBAD MgO growth. We have found a direct correlation between the RHEED generated intensity versus time curve and in-plane texture. Utilizing X-ray diffraction analysis, we have been able to determine the optimum deposition parameters to routinely grow films in batch mode that have a phi scan /spl Delta//spl phi/ from 6 - 7/spl deg/. Coupling the improvements in substrate preparation with optimization of IBAD MgO deposition has allowed for both batch and continuous deposition (termed c-IBAD MgO) on metallic substrates that result in superior superconducting properties. We have demonstrated that deposited meter lengths have had phi scan FWHM values from 8 - 9/spl deg/ with /spl plusmn/ 10% uniformity. Additionally, we have been able to widen the processing zone in our system and coat two, one-meter lengths simultaneously while preserving good texture quality (/spl Delta//spl phi//sub ave/ /spl sim/ 8/spl deg/) and uniformity (60 - 80% of tape length within /spl plusmn/ 5% of /spl Delta//spl phi//sub ave/) for both tapes.