Fabrication and characterization of high-quality (Hg,Re)Ba2CaCu2Oy thin films on LSAT substrates

Abstract

We have succeeded in fabricating high-quality (Hg,Re)Ba2CaCu2Oy ((Hg,Re)-1212) thin films with a thickness of 300 nm on (LaAlO3)0.3–(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates. The films were fabricated by repeating the two-step process, which consists of the preparation of a precursor film and the heat treatment in Hg-vapour atmosphere. For the purpose of improving their crystal quality, the heat treatment in the final process was carried out in a lower Hg-vapour pressure for a longer time. The obtained films had a flat surface and no appreciable outgrowth. The films exhibited a Tc value of 120 K and a Jc value of 4.4 × 106 A cm−2 at 77 K in a self-field, which are substantially higher than those for the films fabricated in higher Hg-vapour atmosphere. Their electrical transport properties in magnetic fields up to 7 T were investigated. Their lower irreversibility fields at 77 K as well as the higher Tc seem consistent with the improved crystallinity. Moreover, a microstrip resonator was made of the high-quality (Hg,Re)-1212 thin film and the input power dependence of the unloaded Q value at 10 GHz could be evaluated at a temperature as high as 100 K.