V0.5Mo0.5Nx/MgO(001): Composition, nanostructure, and mechanical properties as a function of film growth temperature

Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies

“…Previous experimental results show that the hardness (H) of B1 Group-VB (i.e. V, Nb, and Ta) nitrides and carbides is enhanced by anion vacancies [14][15][16][17], consistent with H vs. x trends in V0.5Mo0.5Nx [7][8][9]. Nonetheless, although understoichiometric V0.5Mo0.5Nx is considerably less prone to crack than single-crystal B1 TiN and B1 VN, it is more susceptible to fracturing than stoichiometric V0.5Mo0.5N [7].…”

“…We combine experiments and first-principles simulations to demonstrate that the control of It would be reasonable to assume that a vacancy-induced enhancement in metallic character of anion-deficient B1 TM carbonitridesevidenced by the increased x-ray photoelectron spectra intensities at low binding energies [9,[77][78][79][80][81] Table 3. Calculated tensile-to-shear strength ratios, here used as indicators of fracture resistance.…”

A review of the intrinsic ductility and toughness of hard transition-metal nitride alloy thin films

“…In this DFT-based work, instead of tuning the number of valence electrons by alloying the TM sublattice, they used TaC1-xNx as a model system to investigate alloying on the non-metal anion sublattice and found that both the hardness and elastic modulus of cubic TaC1-xNx decreases with increasing N content (i.e., with increasing VEC), which they attributed primarily to changes in bonding leading toward a more metallic character. [118] and [119]] have demonstrated that polycrystalline, columnar-structure VMoN films grown at Ts = 100 and 300 C also exhibt enhanced toughness and good mechanical properties. In the next sections, we first provide an overview of the structural, electronic, and bonding properties of TM nitrides (2.1); then discuss the effects of alloying (2.2), anion vacancy concentration (2.3), and crystallinity/orientation (2.4) on the mechanical properties of single-crystal pseudobinary TM nitride alloys.…”

“…Motivated by the above results, the effect of N vacancies on the mechanical properties of epitaxial V0.5Mo0.5Ny/MgO(001), with varying stoichiometries (0.55 ≤ y ≤ 1.03), was investigated experimentally [103]. Valence-band x-ray photoelectron spectroscopy (XPS) measurements [118,146,147] provide additional clues as to the origins of enhanced toughness. The valence-band spectra of TM nitrides consists of 2s(N) states, followed by a band which arises from the interaction of p(N) and the metal d-eg(TM) orbitals, and the metallic d-t2g interaction band situated closer to the Fermi level [98,148,149].…”

“…6(b) for N concentrations y = 0.55 (red circles), y = 0.72 (green triangles), and y = 1.03 (blue squares). For comparison, the XPS valence-band spectrum of single-crystal VN0.89 [118] is also shown in Fig. 6(a XPS core-level studies of V0.5Mo0.5Ny films [118,[150][151][152] revealed that the N(1s) photoelectron peaks shift to lower binding energies with decreasing N vacancy concentrations, while the Mo(3p3/2) peaks shift to higher binding energies.…”