Fabrication and Characterization of High-Quality Epitaxial Nanocolumnar Niobium Films with Abrupt Interfaces on YSZ(001)
Fabrication and Characterization of High-Quality Epitaxial Nanocolumnar Niobium Films with Abrupt Interfaces on YSZ(001)
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DOI：
10.1021/acs.jpcc.1c08738
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发表时间：
2022-01
期刊：
影响因子：
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通讯作者：
C. Ramana;Nanthakishore Makeswaran;Vishal Zade;Debabrata Das;Susheng Tan;Shuozhi Xu;I. Beyerlein
中科院分区：
文献类型：
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作者：
C. Ramana;Nanthakishore Makeswaran;Vishal Zade;Debabrata Das;Susheng Tan;Shuozhi Xu;I. Beyerlein
Nb是一种很有前途的难熔金属，在纳米电子学、光电子学、光电子学和能源相关技术中有着广泛的技术应用。然而，为了进一步推动纳米电子学和纳米光子学领域的发展，需要具有良好结构有序的非常高质量的Nb薄膜。尽管在理解Nb在氧化物衬底上的异质外延方面已经取得了很大的进展，但基本的基本机制，特别是实现薄膜与衬底之间的突然界面并且在极端条件下不需要昂贵的设备和/或处理，仍然是一个挑战。在此背景下，我们展示了一种利用简单和工业上广泛采用的溅射沉积方法来稳定YSZ(001)衬底上具有高度有序和陡峭界面的外延、纳米柱面体心立方Nb薄膜的方法。在500°C的YSZ(001)衬底上沉积的90 nm Nb薄膜具有应变的外延结构。X射线衍射和透射电子显微镜分析表明，Nb薄膜的结构质量是由衬底辅助的选择性纳米晶化所决定的。结合颗粒状的形貌和高的结构质量，椭圆偏振光谱和反射率测量的光学性质表明，高反射的Nb薄膜具有更高的光学常数。外延Nb薄膜的表面/界面质量、微结构和光学性质都证实了它具有良好的力学性能。Nb外延膜的硬度和弹性模量分别为18和240 Gpa，这主要归因于在YSZ上生长了致密的纳米Nb外延膜。
Niobium (Nb) is a promising refractory metal with a wide variety of technological applications in nanoelectronics, optoelectronics, photonics, and energy-related technologies. However, to further advance the field of nanoelectronics and nanophotonics, very high-quality Nb films with excellent structural order are needed. While much progress has been made in understanding the heteroepitaxy of Nb on oxide substrates, the underlying fundamental mechanisms, especially to realize films showing abrupt interfaces with the substrate and without needing the expensive equipment and/or processing under extreme conditions, remain a challenge. In this context, herein, we demonstrate an approach to stabilize the epitaxial, nanocolumnar bcc Nb films with highly ordered and abrupt interfaces on YSZ(001) substrates using simple and industrially widely adopted sputter deposition. 90 nm Nb films deposited onto YSZ(001) at 500 °C exhibit a strained, epitaxial structure. As evidenced in X-ray diffraction and transmission electron microscopy analyses, the structural quality of Nb films is driven by substrate-assisted selective nanocrystallization. Coupled with granular morphology and high structural quality, the optical properties measured by spectroscopic ellipsometry and reflectivity indicate highly reflective Nb films with enhanced optical constants. Corroborated with surface/interface quality, microstructure, and optical properties, the epitaxial Nb films exhibit excellent mechanical characteristics. The hardness and elastic modulus of the Nb epitaxial films were 18 and 240 GPa, respectively, which are attributed primarily to the growth of a compact nanocolumnar Nb epitaxial film on YSZ.