Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation
Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation
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DOI：
10.1063/1.4977813
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发表时间：
2017-05-07
影响因子：
3.2
通讯作者：
Schneider, J. M.
中科院分区：
文献类型：
--
作者：
Greczynski, G.;Mraz, S.;Schneider, J. M.
耐火陶瓷薄膜的现代应用，主要作为切削工具和汽车发动机部件上的耐磨涂层，需要兼具优异的机械性能、热稳定性和抗氧化性。具有改进的热稳定性和化学稳定性的过渡金属氮化物涂层的传统设计方法基于与Al的合金化。众所周知，Al在NaCl结构过渡金属氮化物中的溶解度是有限的。因此，最大的挑战是大幅增加Al浓度，同时避免热力学上有利的纤锌矿-AlN相沉淀，这对机械性能不利。在这里，我们使用 VAlN 作为模型系统来说明合成亚稳态单相 NaCl 结构薄膜的新概念，其 Al 含量远远超出传统等离子体工艺获得的溶解度极限。这种过饱和是通过在Ar/N-2气体混合物中对Al靶进行反应混合高功率脉冲磁控溅射和对V靶进行直流磁控溅射期间将70μs长的脉冲衬底偏压与高能Al+金属离子的强烈周期性通量同步，在时间和能量域中分离成膜物质来实现的。由此，Al被植入到由低能V中性子的连续通量形成的立方VN晶粒中。我们表明，Al 置换使得 V1-xAlxN 中亚稳态 Al 溶解度极限前所未有地增加了 42%，从传统方法获得的 x-0.52 增加到 0.75。弹性模量为 325 +/- 5GPa，与密度泛函理论计算结果非常一致，比通过直流磁控溅射生长的相应薄膜高约 50%。将所提出的策略扩展到其他铝离子辅助气相沉积方法或材料系统是简单的，这为生产结合优异机械性能和高抗氧化性的过饱和单相功能陶瓷合金薄膜开辟了道路。由 AIP 出版社出版。
Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-mu s-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N-2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x-0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 +/- 5GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single-phase functional ceramic alloy thin films combining excellent mechanical properties with high oxidation resistance. Published by AIP Publishing.