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

Published

December 7, 2012

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

Pub Type

Journals

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 September 19, 2024)