a Department of Physics, Campus Box 390, University of Colorado, Boulder, CO 80309, USA
b National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401, USA
c Sandia National Laboratories, Albuquerque, NM 87185, USA
Abstract:
Although Tl-based superconductors show higher critical temperatures than other compounds, they suffer some disadvantages, such as surface roughness, non-uniform chemical composition, and the need for excess Tl from a separate source during post-deposition annealing. This paper reports a post-deposition annealing process (in the absence of a separate Tl source) of sequentially deposited metallic layers of Tl:Ba:Ca:Cu with excess amount of thallium in the multilayer. The films show uniform chemical composition and smooth surfaces. Critical temperatures as high as 101 K and critical current densities as high as 1.5 × 104 A/ cm2 at 77 K in zero magnetic field have been achieved.