Structural distortion and suppression of superconductivity in stoichiometric B1-MoN epitaxial thin films

Physical Review B - Condensed Matter and Materials Physics Volume 73 Issue 5 Page 052504- published_at 2006
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Title ( eng )
Structural distortion and suppression of superconductivity in stoichiometric B1-MoN epitaxial thin films
Creator
Baba Kazuya
Source Title
Physical Review B - Condensed Matter and Materials Physics
Volume 73
Issue 5
Start Page 052504
Abstract
Molybdenum nitride films with the NaCl structure (B1-MoN) were epitaxially grown on α- Al2 O3 (001) and MgO(001) substrates at 973 K by pulsed laser deposition (PLD) under nitrogen radical irradiation. The highly crystalline epitaxial films enabled us to determine the three-dimensional cell parameters, which was motivated by theoretical calculations that B1-MoN, a predicted superconductor, is elastically unstable against tetragonal and trigonal distortions. On α- Al2 O3 (001), the B1-MoN phase (composition, Mo1 N0.98) was grown with its (111) planes parallel to the substrate surface. X-ray diffraction analysis with a multiaxes diffractometer detected only a small trigonal lattice distortion [a=0.4219(3) nm, α=89.28(5)°] with an expansion along the [111] direction perpendicular to the substrate surface. The film grown on MgO(001) had the MoN1.03 composition and showed a slight tetragonal distortion (a=0.4213 and c=0.424 nm) due to fitting to the MgO substrate lattice (a=0.4213 nm). These two stoichiometric films showed no superconductivity above 2 K. A lower nitrogen content (MoN0.86) film was obtained on α- Al2 O3 (001) using a higher deposition rate. The corresponding film had a much smaller lattice constant [a=0.4184(3) nm], and a similar distortion [α=89.41(5)°]. The B1- MoN0.86 film showed superconductivity with a transition temperature Tc =4.2 K. The suppression of the superconductivity of the former stoichiometric phase can be interpreted in terms of the lattice expansion.
NDC
Physics [ 420 ]
Language
eng
Resource Type journal article
Publisher
American Physical Society
Date of Issued 2006
Rights
Copyright (c) 2006 American Physical Society
Publish Type Version of Record
Access Rights open access
Source Identifier
[NCID] AA11187113
[ISSN] 1098-0121
[DOI] 10.1103/PhysRevB.73.052504
[DOI] http://dx.doi.org/10.1103/PhysRevB.73.052504