Epitaxial growth of cubic WC (001) on MgO(001)
Epitaxial growth of cubic WC (001) on MgO(001)
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DOI：
10.1016/j.jallcom.2020.158403
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发表时间：
2021-04
影响因子：
6.2
通讯作者：
Peijiao Fang;Baiwei Wang;C. Mulligan;T. M. Murray;Sanjay V. Khare;D. Gall
中科院分区：
文献类型：
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作者：
Peijiao Fang;Baiwei Wang;C. Mulligan;T. M. Murray;Sanjay V. Khare;D. Gall
在 400°C、5 mTorr Ar-CH4 气体混合物（CH4 分数 fCH4= 0.4–6%）中将碳化钨薄膜溅射沉积到 MgO(001) 基底上，通过离子束分析和能量色散 X 射线光谱测定，总 C 与 W 比率 x= 0.57–1.25。立方 WCy 相中的 C-W 比 y 小于 x，范围为 y= 0.47–0.68，根据晶格常数测量结合第一原理计算确定，预测 y= 0.3–1.0 时 ao= (0.4053 + 0.0295y) nm 的增加。这表明立方相通过碳空位稳定，并且层中含有无定形 C，对于 fCH4= 0.4–6%，其体积分数从 4% 增加到 26%。 X 射线衍射 (XRD)θ-2θ 扫描、ω 摇摆曲线和倒易空间图与高分辨率透射电子显微镜 (TEM) 相结合表明外延岩盐结构 WCy(001) 层的生长，与衬底具有立方体上立方体外延关系：(001)WC|| (001)MgO 和 [100]WC|| [100]氧化镁。测得的 8 – 14 nm 的 XRD 面外相干长度几乎与薄膜厚度 d= 10 或 600 nm 无关，表明生长超过 = 10 nm 会导致外延击穿，并导致错误取向的六方或斜方 W2C 晶粒（fCH4≤1%）和立方纳米晶 WCY 晶粒（fCH4>1%）成核。
Tungsten carbide films are sputter-deposited onto MgO(001) substrates at 400 °C in 5 mTorr Ar - CH4gas mixtures with CH4fractionsfCH4= 0.4–6%, yielding total C-to-W ratiosx= 0.57–1.25 as determined by ion beam analyses and energy-dispersive X-ray spectroscopy. The C-to-W ratioyin the cubic WCyphase is smaller thanx, ranging fromy= 0.47–0.68, as determined from lattice constantaomeasurements in combination with first-principle calculations that predict an increasingao= (0.4053 + 0.0295y) nm fory= 0.3–1.0. This suggests that the cubic phase is stabilized by carbon vacancies and that the layers contain amorphous C with a volume fraction increasing from 4% to 26% forfCH4= 0.4–6%. X-ray diffraction (XRD)θ-2θscans,ω-rocking curves, and reciprocal space maps in combination with high-resolution transmission electron microscopy (TEM) indicate the growth of epitaxial rock-salt structure WCy(001) layers with a cube-on-cube epitaxial relationship with the substrate: (001)WC|| (001)MgO and [100]WC|| [100]MgO. The measured XRD out-of-plane coherence length of 8 – 14 nm is nearly independent of the film thicknessd= 10 or 600 nm, suggesting that growth beyondd= 10 nm leads to an epitaxial breakdown and the nucleation of misoriented hexagonal or orthorhombic W2C grains forfCH4≤ 1% and cubic nanocrystalline WCygrains forfCH4> 1%.