C-axis oriented (Hg,Ti)-based superconducting films with Tc≳125 K

Thin films with mostly (Hg,Tl)1Ba2Ca3Cu2O8+δ [(Hg,Tl)-1223] phase have been fabricated by radio frequency magnetron sputtering of precursor films and post-annealing method. The doping of a small amount of thallium in the film is helpful to the formation of the three-layer CuO2 compound. These films have a highly oriented structure with the c-axis perpendicular to the film surface. Resistivity measurements show that the films after annealing at 300°C for 1 h in O2 have the superconducting transition temperature of Tc(onset)=133 K and Tc(zero)=127 K. Scanning electron micrographs of the film reveal platelike micrometer-size grains coalesce to cover the substrate surface.