The effect of growth conditions and vacancies on the electronic and mechanical properties of cubic Mo2N; A DFT study

Lahmer, M.A.

doi:10.1016/j.cocom.2019.e00405

Cited by 4 publications

(4 citation statements)

References 36 publications

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“…We used for the analysis a fixed Poisson ratio of ν = 0.35 for each sample. This value was calculated from DFT-computed elastic constants on the γ-Mo 2 N compound 26 and assuming a (001) crystal orientation, ν ¼ C 12 /(C 11 þ C 12 ).…”

Section: B Characterization Techniquesmentioning

confidence: 99%

“…Here, we observe only a moderate continuous increase of C 44 by ∼10%-15% for both experimental and predicted DFT values until x = 0.5. It is demonstrated from DFT simulations by Lahmer 26 that insertion of 3% V Me and 6% V N vacancies into γ-Mo 2 N leads to the reduction of all elastic constants, with a larger effect observed for V Me . Here, when the ternary Mo 1−x Al x N solid solution is formed, the influence of vacancy concentration (10% V Me or V N are considered here) on C 44 is more complex and may change as a function of Al fraction.…”

Section: Elastic and Mechanical Propertiesmentioning

confidence: 99%

“…19 This has stimulated some recent investigations aiming at determining the phase stability under different deposition conditions, as well as understanding the influence of point defects (metal and nitrogen vacancies) at the origin of stabilization of cubic MoN x compounds with off-stoichiometry. [20][21][22][23][24][25][26] The optical properties of an epitaxial cubic MoN x film (x = 0.69) are also very appealing for ultraviolet technologies, as this compound exhibits negative and near-zero real permittivity combined with room temperature resistivity as low as 250 μΩ cm. 27 The presence of nitrogen vacancies in MoN x is believed to impart its unique optical performance.…”

Section: Introductionmentioning

confidence: 99%

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Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Anğay

Löfler

Têtard

et al. 2020

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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In this work, the structural and mechanical properties of ternary Mo-Al-N alloys are investigated by combining thin film growth experiments and density functional theory (DFT) calculations. Mo 1−x Al x N y thin films (∼300 nm thick), with various Al fractions ranging from x = 0 to 0.5 and nitrogen-to-metal (Al + Mo) ratio ranging from y = 0.78 to 1.38, were deposited by direct-current reactive magnetron cosputtering technique from elemental Mo and Al targets under Ar + N 2 plasma discharges. The Al content was varied by changing the respective Mo and Al target powers, at a fixed N 2 (20 SCCM) and Ar (25 SCCM) flow rate, and using two different substrate temperatures T s = 350 and 500°C. The elemental composition, mass density, crystal structure, residual stress state, and intrinsic (growth) stress were examined by wavelength dispersive x-ray spectroscopy, x-ray reflectivity, x-ray diffraction, including pole figure and sin 2 ψ measurements, and real-time in situ wafer curvature. Nanoindentation tests were carried out to determine film hardness H and elastic modulus E IT , while the shear elastic constant C 44 was measured selectively by surface Brillouin light spectroscopy. All deposited Mo 1−x Al x N y films have a cubic rock-salt crystal structure and exhibit a fiber-texture with a [001] preferred orientation. The incorporation of Al is accompanied by a rise in nitrogen content from 44 to 58 at. %, resulting in a significant increase (2%) in the lattice parameter when x increases from 0 to 0.27. This trend is opposite to what DFT calculations predict for cubic defect-free stoichiometric Mo 1−x Al x N compounds and is attributed to variation in point defect concentration (nitrogen and metal vacancies) when Al substitutes for Mo. Increasing T s from 350 to 500°C has a minimal effect on the structural properties and phase composition of the ternary alloys but concurs to an appreciable reduction of the compressive stress from −5 to −4 GPa. A continuous increase and decrease in transverse sound velocity and mass density, respectively, lead to a moderate stiffening of the shear elastic constant from 130 to 144 GPa with increasing Al fraction up to x = 0.50, and a complex and nonmonotonous variation of H and E IT is observed. The maximum hardness of ∼33 GPa is found for the Mo 0.81 Al 0.19 N 1.13 film, with nitrogen content close to the stoichiometric composition. The experimental findings are explained based on structural and elastic constant values computed from DFT for defect-free and metal-or nitrogen-deficient rock-salt MoAlN compounds.

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Section: B Characterization Techniquesmentioning

confidence: 99%

Section: Elastic and Mechanical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Anğay

Löfler

Têtard

et al. 2020

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…Density functional theory (DFT) is a powerful method to study not only perfect crystals but also the effect of defects on the properties of materials [24]. In addition, the formation energy (E f ) of defects can be calculated which paves the way for defect engineering in materials [25].…”

Section: Introductionmentioning

confidence: 99%

Vacancies and substitutional defects in multicomponent diboride Ti_0.25Zr_0.25Hf_0.25Ta_0.25B₂: first-principle study

Matas¹,

Farhadizadeh²,

Houška³

2021

J. Phys.: Condens. Matter

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We study the hard and electrically conductive multicomponent diboride Ti0.25Zr0.25Hf0.25Ta0.25B2 with high thermal stability by ab initio calculations. We focus on the effect of defects (either vacancies or C atoms, both relevant for numerous experiments including our own) on material characteristics. Different types, concentrations and distributions of defects were investigated, and the configurations leading to the lowest formation energies were identified. We show that the replacement of B by C is more unfavorable than the formation of B vacancies. We show that vacancies prefer to coalesce into a larger planar void, minimizing the number of broken B B bonds and the volume per atom, while carbon substitutions at boron sites do not prefer coalescence and tend to minimize the number of C-C bonds. We show the effect of vacancies on mechanical and electronic properties, and use the results to explain experimental data.

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RHOMBOHEDRAL NIOBIUM MONOXIDE: THEORETICALLY PREDICTED HIGH- PRESSURE PHASE NbO

et al. 2022

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The effect of growth conditions and vacancies on the electronic and mechanical properties of cubic Mo2N; A DFT study

Cited by 4 publications

References 36 publications

Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Vacancies and substitutional defects in multicomponent diboride Ti_0.25Zr_0.25Hf_0.25Ta_0.25B₂: first-principle study

RHOMBOHEDRAL NIOBIUM MONOXIDE: THEORETICALLY PREDICTED HIGH- PRESSURE PHASE NbO

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The effect of growth conditions and vacancies on the electronic and mechanical properties of cubic Mo2N; A DFT study

Cited by 4 publications

References 36 publications

Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects

Vacancies and substitutional defects in multicomponent diboride Ti0.25Zr0.25Hf0.25Ta0.25B2: first-principle study

RHOMBOHEDRAL NIOBIUM MONOXIDE: THEORETICALLY PREDICTED HIGH- PRESSURE PHASE NbO

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Vacancies and substitutional defects in multicomponent diboride Ti_0.25Zr_0.25Hf_0.25Ta_0.25B₂: first-principle study