Laser-ablated epitaxial LaAlO₃ buffer layers on biaxially textured Ni substrates for superconducting tapes

Reported here is a new epitaxial buffer layer configuration on biaxially textured Ni substrates for high temperature superconducting films. The hetero-epitaxial LaAlO₃/SrTiO₃/CeO₂/Ni structure was grown using pulsed laser deposition and is the first demonstrated epitaxial deposition of LaAlO₃ on a metal substrate. This buffer configuration was designed specifically for, but is not limited to, the Tl-based superconducting materials for which LaAlO₃ has been shown to be the optimum substrate to date. The epitaxy and crystal quality of these layers were investigated using X-ray diffraction including θ/2θ and pole figure analysis, which showed that the consistency of the SrTiO₃ orientation requires further optimization. Atomic force microscopy measurements revealed initial films that, although epitaxial, have a cracked morphology. The formation mechanism of these cracks and their subsequent elimination are discussed.