Epitaxial NbCxN1-x(001) layers: Growth, mechanical properties, and electrical resistivity

SURFACE & COATINGS TECHNOLOGY

卷:277

Article

Zhang, K.^1,2  Balasubramanian, K.¹  Ozsdolay, B. D.¹  Mulligan, C. P.^1,3  Khare, S. V.⁴  Zheng, W. T.²  Gall, D.¹ 

[1] Rensselaer Polytech Inst, Dept Mat Sci & Engn, Troy, NY 12180 USA

[2] Jilin Univ, Dept Mat Sci, Key Lab Mobile Mat, State Key Lab Superhard Mat,MOE, Changchun 130012, Peoples R China

[3] Benet Labs, US Army Armament Res Dev & Engn Ctr, Watervliet, NY 12189 USA

[4] Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA

关键词: Niobium nitride;    Niobium carbide;    Elastic constants;    Mechanical properties;    Resistivity;    Hardness;   

DOI  :  10.1016/j.surfcoat.2015.07.025

来源: Elsevier

【 摘 要 】

NbCxN1-x layers were deposited on MgO(001) by reactive magnetron co-sputtering from Nb and graphite targets in 5 mTorr pure N-2 at T-s = 600-1000 degrees C. The anion-to-Nb ratio of 1.09 +/- 0.05 is independent of T-s and indicates a nearly stoichiometric rock-salt structure Nb(N,C) solid solution. In contrast, the C-to-N ratio increases from 0.20-0.59 for T-s = 600-1000 degrees C, which is attributed to a low C sticking probability at high N surface coverage at low T-s. Layers grown at T-s >= 700 degrees C are epitaxial single-crystals with a cube-on-cube relationship to the substrate, (001)(NbcN)parallel to(001)(MgO) and [100](NbcN)parallel to[100](MgO), as determined from X-ray diffraction theta-2 theta and phi-scans. Reciprocal space mapping on a NbC0.37N0.63 layer deposited at T-s = 1000 degrees C indicates an in-plane compressive strain of -0.4% and a relaxed lattice constant of 4.409 +/- 0.009 angstrom. The lattice constant of NbCxN1-x increases with x, consistent with a linear increase predicted by first-principles density functional calculations. The calculated bulk modulus, 307 GPa for NbN and 300 GPa for NbC, is nearly independent of x. Similarly, c(11) increases slightly from 641 to 666 GPa, but c(12) decreases considerably from 140 to 117 GPa, and c(44) more than doubles from 78 to 171 GPa as x increases from 0 to 1, indicating a transition from ductile NbN to brittle NbC. This also results in an increase in the predicted isotropic elastic modulus from 335 to 504 GPa, which is in good agreement with the measured 350 +/- 12 GPa for NbCxN1-x(001) with x = 0.19-031. The hardness H = 22 +/- 2 GPa of epitaxial NbCxN1-x layers is nearly independent of x = 0.19-0.37 and T-s = 700-1000 degrees C, but is reduced to H = 18.2 +/- 0.8 GPa for the nanocrystalline layer deposited at T-s = 600 degrees C. The electrical resistivity decreases strongly with increasing T-s < 800 degrees C, due to increasing crystalline quality, and is 262 +/- 21 mu Omega-cm at room temperature and 299 +/- 22 mu Omega-cm at 77 K for T-s >= 800 degrees C, indicating weak carrier localization due to the random distribution of C atoms on anion sites. (C) 2015 Elsevier B.V. All rights reserved.

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