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This content will become publicly available on March 29, 2019

Title: Vapor annealing synthesis of non-epitaxial MgB 2 films on glassy carbon

Here, we describe the fabrication and characterization of 25–800 nm thick MgB 2 films on glassy carbon substrates by Mg vapor annealing of sputter-deposited amorphous B films. Results demonstrate a critical role of both the initial B film thickness and the temperature–time profile on the microstructure, elemental composition, and superconducting properties of the resultant MgB 2 films. Films with thicknesses of 55 nm and below exhibit a smooth surface, with a roughness of 1.1 nm, while thicker films have surface morphology consisting of elongated nano-crystallites. The suppression of the superconducting transition temperature for thin films scales linearly with the oxygen impurity concentration and also correlates with the amount of lattice disorder probed by Raman scattering. The best results are obtained by a rapid (12 min) anneal at 850°C with large temperature ramp and cooling rates of ~540°C min -1. Such fast processing suppresses the deleterious oxygen uptake.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-743108
Journal ID: ISSN 0953-2048; 898052
Grant/Contract Number:
AC52-07NA27344; 17-ERD-040
Type:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 31; Journal Issue: 5; Journal ID: ISSN 0953-2048
Publisher:
IOP Publishing
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; Superconductivity; MgB2; Thin Films; Levitation
OSTI Identifier:
1458621