Pulsed laser deposition of niobium thin films for in-situ device fabrication and their superconducting properties

Abstract

Here, we studied the crystallographic and superconducting properties of niobium thin films grown by pulsed laser deposition. Depending on laser fluence our samples showed a critical temperature of up to 8.4 K and critical current densities of 3.0 · 106 A/cm2 at 4.2 K. X-ray diffraction measurements and TEM images suggest a granular structure with a preferred orientation of the (110) lattice plane parallel to the substrate surface. The superconducting properties of our films are significantly influenced by this granularity and the oxygen content in the film. We discuss the temperature dependence of the critical current density in the framework of an crossover from Ginzburg-Landau to Ambegaokar-Baratoff type behaviour. According to this the current transport is mainly dominated by Josephson-tunnelling in a granular network.