| Autor: |
Gall, D., Shin, C.-S., Spila, T., Ode´n, M., Senna, M. J. H., Greene, J. E., Petrov, I. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 3/15/2002, Vol. 91 Issue 6, p3589, 9p, 2 Black and White Photographs, 3 Graphs |
| Abstrakt: |
CrN layers, 0.5 μm thick, were grown on MgO(001) at T[sub s]=570–775 °C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N[sub 2] discharges at 20 mTorr. Layers grown at T[sub s]≤700 °C are stoichiometric single crystals exhibiting cube-on-cube epitaxy: (001)[sub CrN]||(001)[sub MgO] with [100][sub CrN]||[100][sub MgO]. At higher temperatures, N[sub 2] desorption during deposition results in understoichiometric polycrystalline films with N fractions decreasing to 0.35, 0.28, and 0.07 with T[sub s]=730, 760, and 775 °C, respectively. The surface morphologies of epitaxial CrN(001) layers were found to depend strongly on the incident ion-to-metal flux ratio J[sub N[sub 2][sup +]]/J[sub Cr] which was varied between 1.7 and 14 with the ion energy maintained constant at 12 eV. The surfaces of layers grown with J[sub N[sub 2][sup +]]/J[sub Cr]=1.7 consist of self-organized square-shaped mounds, due to kinetic roughening, with edges aligned along orthogonal <100> directions. The mounds have an average peak-to-valley height =5.1 nm and an in-plane correlation length of =0.21 μm. The combination of atomic shadowing by the mounds with low adatom mobility results in the formation of nanopipes extending along the growth direction. Increasing J[sub N[sub 2][sup +]]/J[sub Cr] to 14 leads, due to increased adatom mobilities, to much smoother surfaces with =2.5 nm and =0.52 μm. Correspondingly, the nanopipe density decreases from 870 to 270 μm[sup -2] to <20 μm[sup -2] as J[sub N[sub 2][sup +]]/J[sub Cr] is increased from 1.7 to 6 to 10. The hardness of dense CrN(001) is 28.5±1 GPa, but decreases to 22.5±1 GPa for layers containing significant nanopipe densities. The CrN(001) elastic modulus, 405±15 GPa, room-temperature resistivity, 7.7×10[sup -2] Ω cm, and relaxed lattice constant, 0.4162±0.0008 nm, are independent of J[sub N[sub 2][sup +]]/J[sub Cr].... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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