Film/substrate interactions and superconducting properties of Tl(Ba1−xSrx)2Ca2Cu3Oy thin films on (001) SrTiO3 and SrTiO3-buffered (001) MgO substrates

• Published in: Journal of materials research 1998-08, Vol.13 (8), p.2057-2066
• Main Authors: Bramley, A. P., Grovenor, C. R. M., Goringe, M. J., O'Connor, J. D., Jenkins, A. P., Dew-Hughes, D., Reschauer, N., Wagner, H. H., Brozio, W., Spreitzer, U., Renk, K. F.
• Format: Article
• Language: English
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.1998.0289

We have developed a process for the fabrication of (001) oriented SrTiO3 buffer layers onto (001) MgO substrates by rf magnetron sputtering followed by a post-deposition heat treatment in air. Precursor films with Tl :Ba : Ca : Cu ratio 2 : 2 : 2 : 3 were deposited by dc magnetron sputtering onto both these buffered substrates and directly onto (001) SrTiO3 single-crystal substrates, and thalliated at elevated temperatures. Because of Sr diffusion from the substrate/buffer layer, and its subsequent substitution for Ba in the superconducting film, the single Tl–O layer phase Tl(Ba1−xSrx)2Ca2Cu3Oy was stabilized. Diffusion of Ba and Ca in the opposite direction led to the formation of a Ba–Ca–Ti–O compound at the interface. The Tl(Ba1xSrx)2Ca2Cu3Oy films typically have superconducting transition temperatures (Tc's) > 103 K and critical current densities (Jc's) > 2.9 × 105 A cm−2 at 77 K. Rs values measured on these films and scaled to 10 GHz were 3.0 mΩ at 80 K and