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Superconductivity in Nb-Sn thin films of stoichiometric and off-stoichiometric compositions

Published

Author(s)

Matthijs Mentink, John E. Bonevich, Marc Dhalle, Daniel Dietderich, Arno Godeke, Frances Hellman, Herman Ten Kate

Abstract

Binary Nb-Sn thin film samples are fabricated and characterized in terms of their composition, morphology and superconducting properties. Nb-Sn is magnetron-sputtered onto heated R-plane sapphire substrates at 700 C, 800 C, and 900 C, using a custom-built heater assembly. Samples are cut into strips, where each strip has a unique composition ranging from (0.19 to 0.25) atom fraction Sn and is homogeneous along it's length within an uncertainty of 0.005 atomic fraction Sn, as determined by Scanning Electron Microscopy - X-ray Energy Dispersive Spectroscopy (SEM-XEDS). For a subset of the samples, Nb-Sn is selectively etched away, using a mixture of 0.065 volume fraction hydro-fluoric and 0.19 volume fraction nitric acid, with an etching rate of 6 nm/s +/- 1 nm/s. Surface and cross-section morphology are investigated using SEM and Scanning Transmission Electron Microscopy (STEM), revealing a dense, columnar, poly-crystalline grain structure. X-ray Diffraction (XRD) measurements indicate a highly textured film that is (100) oriented out-of-plane and random in-plane. The critical temperature Tc (ranging from 9.8 K to 17.9 K), critical magnetic field mu0Hc2 (ranging from 12.5 T to 31.3 T), Residual Resistivity Ratio (RRR), and normal state resistivity 0 are measured and found to be broadly consistent with literature data on bulk Nb3Sn.
Citation
Applied Superconductivity

Keywords

thin film, superconductor, stoichiometry, SEM, STEM, XEDS

Citation

Mentink, M. , Bonevich, J. , Dhalle, M. , Dietderich, D. , Godeke, A. , Hellman, F. and Ten Kate, H. (2012), Superconductivity in Nb-Sn thin films of stoichiometric and off-stoichiometric compositions, Applied Superconductivity (Accessed July 6, 2022)
Created December 6, 2012, Updated October 12, 2021