Growth and characterization of 2 inch double-sided Tl2Ba2CaCu2O8 thin films on LaAlO3 substrates

Superconducting Tl2Ba2CaCu2O8 thin films (Tl-2212) have been reproducibly fabricated on both sides of 2 inch LaAlO3(001) substrates by using a so-called two-step process. A simple and flexible horizontal arrangement inside the crucible during thallination has been proposed, to ensure a good convection of thallous oxide vapor around the film surface, and thus a high film quality on both sides. A good uniformity over the whole area of the films has been realized. The films are strongly textured, with the c-axis perpendicular to the substrate surface, and they show the fourfold symmetry of the tetragonal crystal structure. The full width at half maximum of the (002) peak for both films on the best sample is 0.43° and 0.55° respectively. The films exhibit flat terraces with particles and shallow holes, but free of microcracks. The superconducting critical temperatures fall in the range 105–108.5 K. The critical current densities are between 1.0 × 106 and 4.8 × 106 A cm−2 at 77 K. The microwave surface resistances at the central area of the films are around 500 μΩ at 77 K and 10 GHz. These films are suitable for microwave applications.