AVS 60th International Symposium and Exhibition
    Thin Film Friday Sessions
       Session TF+EM+NS+SS-FrM

Paper TF+EM+NS+SS-FrM6
Toughness Enhancement in Hard Single-crystal V0.5Mo0.5N/MgO(001) Thin Films

Friday, November 1, 2013, 10:00 am, Room 104 A

Session: Thin Film: Growth and Characterization III
Presenter: H. Kindlund, Linköping University, Sweden
Authors: H. Kindlund, Linköping University, Sweden
J. Lu, Linköping University, Sweden
I.G. Petrov, University of Illinois at Urbana Champaign
J.E. Greene, University of Illinois at Urbana Champaign
L. Hultman, Linköping University, Sweden
Correspondent: Click to Email
Hardness is an essential property for a wide range of applications, while for some purposes one also needs ductility to avoid film failure in ceramic films exposed to high stresses. Using VN as a model system, we demonstrate that VMoN alloys exhibit not only enhanced hardness, but impressive increased ductility, i.e. toughness, and study the effect of N vacancies on mechanical properties of pseudobinary NaCl-structure transition metal nitride, VMoN.

V0.5Mo0.5Nx thin films with 0.55 ≤ x ≤ 1.03, as determined by RBS, are deposited on MgO(001) substrates by dual reactive magnetron sputtering. For the entire N composition range x, we obtain single-crystal B1-structure V0.5Mo0.5Nx, as determined by XRD and TEM analyses. RLM results indicate that the films are relaxed with lattice parameters varying from a = 4.12 Å for x = 0.55 to a = 4.19 Å for x = 1.03, increasing with increasing N content. The nanoindentation hardness H increases as N-vacancy concentration increases, from H = 18 GPa (x=1.03), to 20 GPa (x=0.94), 21 GPa (x=0.72), to 26 GPa (x=0.55), while the elastic modulus is maintained essentially constant. In addition, while nanoindented VN and TiN reference samples suffer from severe cracking typical of brittle ceramics, V0.5Mo0.5Nx films do not crack. Instead, they exhibit material pile-up around nanoindents, characteristic of plastic flow in ductile materials.