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−xAl_xN_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 + N₂ plasma discharges. The Al content was varied by changing the respective Mo and Al target powers, at a fixed N₂ (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 $\mathrm{si}{\mathrm{n}}^2\psi$ 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 C₄₄ was measured selectively by surface Brillouin light spectroscopy. All deposited Mo_1−xAl_xN_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−xAl_xN 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_0.81Al_0.19N_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.

中文翻译：

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直流反应磁控共溅射沉积Mo-Al-N薄膜的结构，应力和力学性能：点缺陷的作用

在这项工作中，通过结合薄膜生长实验和密度泛函理论（DFT）计算来研究三元Mo-Al-N合金的结构和力学性能。沉积了Mo _1-x Al _x N _y薄膜（约300 nm厚），其中各种Al含量在x = 0至0.5范围内，氮与金属（Al + Mo）之比在y = 0.78至1.38之间。在Ar + N ₂等离子体放电下，通过直流反应磁控管共溅射技术从元素Mo和Al靶上获得。通过在固定的N ₂（20 SCCM）和Ar（25 SCCM）流速下并使用两个不同的基板温度T _s改变各自的Mo和Al目标功率来改变Al含量= 350和500°C。通过波长色散X射线光谱，X射线反射率，X射线衍射（包括极图和X射线衍射）检查了元素组成，质量密度，晶体结构，残余应力状态和固有（生长）应力。$\mathrm{si}{\mathrm{ñ}}^2\psi$测量和实时原位晶圆曲率。进行纳米压痕测试以确定膜硬度H和弹性模量E _IT，同时通过表面布里渊光谱法选择性地测量剪切弹性常数C ₄₄。全部沉积的Mo _1-x Al _x N _y薄膜具有立方岩盐晶体结构，并显示具有[001]优先取向的纤维纹理。Al的引入伴随着氮含量从44at。％增加到58at。％。％，当x从0增加到0.27时，导致晶格参数显着增加（2％）。这种趋势是相反的什么DFT计算预测立方无缺陷的化学计量的Mo _1-x的Al _X Ñ化合物和归因于点缺陷浓度（氮和金属空位）变化时Al取代Mo的增加Ť_小号温度从350到500°C对三元合金的结构性能和相组成影响很小，但会导致压缩应力从-5 GPa显着降低到-4 GPa。横向声速和质量密度的连续增加和减少分别导致剪切弹性常数从130 GPa适度变强至144 GPa，其中Al分数增加到x = 0.50，H和E的变化复杂且非单调_IT观察。Mo _0.81 Al _0.19 N _1.13的最大硬度为〜33 GPa氮含量接近化学计量组成的薄膜。基于DFT计算的无缺陷和金属或氮缺乏的岩盐MoAlN化合物的结构常数和弹性常数值，对实验结果进行了解释。