Hg-based cuprate superconducting thin films prepared on CeO₂buffered R-plane sapphire substrate

Abstract

Hg-Ba-Ca-Cu-O films have been grown on CeO 2 /R-plane sapphire substrates using a two-step process. First, a 200 nm thick Ba-Ca-Cu-(O, F) precursor film was prepared by sequential evaporation, then Hg-Re-Ba-Ca-Cu-O pellets as a source of Hg-vapour were applied using heat treatment. The prepared films were continuous with sufficient adhesion to the substrate and a maximum zero-resistance critical temperature of T C0 = 118 K. The x-ray diffraction measurements of all the prepared films confirmed the Hg-1212 phase as well as the minor Hg-1223 phase in some cases. We found that the best results were obtained at the mercuration temperature of 775 • C and an optimal annealing time within the range 0.5-5 h. The superconducting properties of the films prepared under unsuitable conditions were mostly improved after annealing in oxygen atmosphere. Darker parts of the film exhibited a different surface morphology and the presence of the Hg-1223 phase in plate-like grains.

Fabrication and characterization of high-quality (Hg,Re)Ba2CaCu2Oythin films on LSAT substrates

“…These materials are considered promising materials for electronic devices such as superconducting quantum interference devices (SQUIDs) and superconducting filters, which can operate at a high temperature above 100 K. For microwave devices, a film thickness typically larger than 300 nm and a low dielectric loss of a substrate are required. Recently, Hg-based thin films fabricated on LaAlO 3 (LAO) substrates and CeO 2 -buffered R-plane sapphire substrates were reported [4,5]. Inoue et al also tried fabricating 300 nm thick Re-doped Hg-1212 thin films on (LaAlO 3 ) 0.3 -(SrAl 0.5 Ta 0.5 O 3 ) 0.7 (LSAT) substrates whose dielectric constant is comparable to LAO.…”