Growth and property analysis of large-area epitaxial Tl-2212 high temperature superconducting films

Abstract

The extensive use of large-area high temperature superconducting (HTS) thin films has emerged in superconducting microwave devices. The interest in Tl-based HTS films arises from their high critical temperature (Tc), allowing the microwave device made on Tl films to work above the liquid nitrogen temperature zone. Here, we introduce a simplified two-step method to fabricate high-quality Tl2Ba2CaCu2O8 (Tl-2212) films on 2-inch LaAlO3 substrates. This method enables the preparation of Tl-2212 films to be easy and repeatable, promoting the theoretical research and practical applications of Tl-based films. Based on the high reproducibility of this fabricating process, we studied the superconducting properties of Tc, the critical current density Jc (77 K, zero field) and surface resistance (Rs) of 2-inch Tl-2212 films. Results show that the Tc values of the sample films prepared at different conditions vary from 99 K to 103 K, depending on the oxygen content; the Jc of the films ranges from 0.7 to 1.8 MA/cm2, relying on the surface roughness. On the basis of the two-fluid model, the influence of Jc on Rs of the Tl-2212 films is incorporated to explain the variation of Rs in different samples.