Critical current densities of submillimeter single-grain TL-2223 superconducting thin film

Abstract

Large single-crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x (Tl-2223) with sizes up to 150 mu m x 150 mu m x 1 mu m are obtained on both MgO(100) and LaAlO3 (100) substrates by a single-target de-sputtering process followed by appropriate postannealing at temperatures around 910 degrees C. Such superconducting grains were isolated and patterned into 10-mu m-wide bridges by reactive ion etching. The etching process was found to only minimally affect the transition temperature, T-c, typically around 110 K, of the films. Although there was evidence that these films were indeed two-dimensional in nature, the critical current densities, J(c), were greater than 10(6) A/cm(2) at temperatures below 90 K. At lower temperatures, e.g., T = 30 K, the J(c) value of these films remains well above 10(6) A/cm(2) even with magnetic fields as large as 7 T applied parallel to the c-axis of the grains. The results are in sharp contrast to the low J(c) values expected from the low-dimensionality nature of this system.