As-deposited near-single crystalline high T_c and J_c superconducting thin films by a pulsed lased deposition process

Abstract

As-deposited high T_c superconducting Y₁Ba₂Cu₃O_7-x films with zero resistance temperatures of 89 K and critical current densities about 0.7×10⁶ A/cm² at 77 K have been reproducibly fabricated at a substrate holder temperature at 650°C, using pulsed laser deposition, without post-annealing. One key to these results is the injection of gaseous oxygen into laser produced plume just in front of the target. In this way, the correct amount of oxygen is incorporated into the as-grown film so that post-deposition treatment becomes unnecessary. Axial ion channeling in these as-deposit high T_c superconducting films on (100) SrTiO₃ and X-ray photoelectron spectroscopy (XPS) on the film surfaces were performed. Angular yield profile near the film surface for Ba, and the surface peak intensity were measured using 3 MeV He ions. For channeling normal to the substrate a minimum yield of 7%, compared to 3% for single crystals, was obtained. The results of ion channeling and XPS studies indicate that the as-deposited films have good crystallinity as well as toichiometry to within 1 nm of the film surface. The in-situ growth of such high T_c and J_c films is an important step in the use of the laser deposition technique to fabricate multilayer structures and the surface perfection is of importance in tunneling devices such as Josephson junctions.