| AVS 62nd International Symposium & Exhibition | |
| Advanced Surface Engineering | Monday Sessions |
| Session SE+AS+NS+TR-MoM |
| Session: | Nanostructured Thin Films and Coatings |
| Presenter: | Brian Ozsdolay, Rensselaer Polytechnic Institute |
| Authors: | B.D. Ozsdolay, Rensselaer Polytechnic Institute K. Balasubramanian, Rensselaer Polytechnic Institute C.P. Mulligan, U.S. Army Armament Research Development & Engineering Center, Benét Laboratories M.J. Guerette, Rensselaer Polytechnic Institute L. Huang, Rensselaer Polytechnic Institute D. Gall, Rensselaer Polytechnic Institute |
| Correspondent: | Click to Email |
WNx layers, 1.45-μm-thick, were deposited by reactive magnetron sputtering on MgO(001), MgO(111), and Al2O3(0001) in 20 mTorr N2 at Ts = 500-800 °C. X-ray diffraction ω-2θ scans, ω-rocking curves, φ scans, and reciprocal space maps show that all layers deposited from 500-700 °C exhibit the cubic rock-salt structure, with a relaxed lattice constant that decreases from 4.299 to 4.171 Å as the N-to-W ratio decreases from x = 1.20 for Ts = 500 °C to x = 0.83 for Ts = 700 °C, as measured by energy dispersive and photoelectron spectroscopies. Ts = 500-600 °C yields a polycrystalline 111-textured microstructure on all substrates. In contrast, deposition at 700 °C results in epitaxial growth of WN(111) and WN(001) on MgO(111) and MgO(001), respectively, while deposition on Al2O3(0001) yields a 111-preferred orientation, misoriented cubic WN grains as well as N-deficient BCC W. Ts = 800 °C causes nitrogen loss and WNx layers with primarily BCC W grains and x = 0.04-0.06. The measured elastic modulus ranges from 110-260 GPa for Ts = 500-700 °C and decreases with increasing N-content, and increases to 350 GPa for Ts = 800 °C. For samples deposited at Ts = 700 °C, nanoindentation on WN on MgO(001), MgO(111), and Al2O3(0001) provides hardness values of 9.8 ± 2.0, 12.5 ± 1.0, and 10.3 ± 0.4 GPa, and elastic moduli of 240±40, 257±13, and 242±10 GPa, respectively. The corresponding shear moduli measured by Brillouin light scattering are 127±2 GPa, 121±2 GPa and 115±2 GPa. MoNx layers, 1- μm-thick, deposited on MgO(001) also exhibit a cubic rock salt structure with x decreasing from 1.18 for Ts = 500 and 600 °C to x = 0.76 for Ts = 800 °C but remaining approximately constant for Ts = 800-1000 °C. Layers with Ts > 700 °C contain both epitaxial MoNx(001) and 111-oriented grains. The out-of-plane lattice constant decreases from 4.22 to 4.18 Å for 111 oriented grains and from 4.17 to 4.06 Å for epitaxial 001-oriented grains, as Ts is increased from 700 °C to 1000 °C.