Prefabricated Metal Nanorods on Biaxially-Textured Templates on Flexible Substrates for REBCO Superconductors

As an alternative to the introduction of flux pinning centers in RE-Ba-Cu-O (REBCO, RE = rare earth) films by the self-assembly process, we have explored prefabrication of metal nanorods on biaxially-textured templates on flexible substrates followed by REBCO film deposition. This approach provides an opportunity to control nanorod features such as size, shape, density, and orientation, which are difficult to achieve using self-assembly of nanoscale defects during in-situ growth. Successful growth of various metal nanorods such as Ni and Co on biaxially-textured substrates has been accomplished using high-energy ion bombardment of polycarbonate films for template formation followed by metal electrodeposition and polycarbonate removal. Ni nanorods of length up to 2 μm, diameter as small as 10-20 nm, variable orientation and density as high as 5 × 10¹⁰/cm² have been grown successfully on biaxially textured templates on flexible metal substrates. In order to provide a suitable interface between the metal nanorods and the subsequently deposited REBCO film, a strontium titanate (SrTiO₃) film was deposited to the nanorods by solution spin coating, which was also (200) textured on the substrate surface.