Abstract
This review contains recent information on the properties of Tl-Ca-Ba-Cu-O thin films. The conditions for the Tl-Ca-Ba-Cu-O film growth by sputtering and by molecular beam deposition are described. The highest zero resistance temperature is 116K. The as-deposited films are insulators, but they become superconductive after being annealed in oxygen at 880930°C for 10min. After post-annealing, the films on MgO and SrTiO3 substrates exhibit zero resistivity at 116K and 80K, respectively. The crystal structures of the films are tetragonal, so that the surface morphologies are essentially twin free.
Using a SQUID magnetization measuring technique in a parallel field, it was found the randomly oriented polycrystalline Tl-Ca-Ba-Cu-O thin film shows a critical current density (Jc) in excess of 1.5×106A/cm2 at 50K. This large Jc value indicates the presence of surface pinning, which is much stronger than any bulk pinning observed by a measurement in a perpendicular field.
It was also found that the microbridge DC-SQUID's fabricated from the Tl-Ca-Ba-Cu-O films patterned by maskless etching using focused ion beam (FIB) processes, operates up to 95K.
