Epitaxial TiN/MgO multilayers with ultrathin TiN and MgO layers as hyperbolic metamaterials in visible region
Epitaxial TiN/MgO multilayers with ultrathin TiN and MgO layers as hyperbolic metamaterials in visible region
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DOI：
10.1016/j.mtphys.2020.100316
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发表时间：
2021
影响因子：
11.5
通讯作者：
Jijie Huang;Di Zhang;Haiyan Wang
中科院分区：
文献类型：
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作者：
Jijie Huang;Di Zhang;Haiyan Wang
具有金属-电介质堆叠的多层被认为是生产双曲超材料（HMM）的有效方法。然而，为低损耗 HMM 制造具有高结晶度的超薄金属层非常具有挑战性。在这项工作中，TiN 被用作贵金属的替代候选材料，并且设计了具有不同层数和层厚度的 TiN/MgO 多层膜。微观结构研究表明，通过改变总层数，将TiN纳米层的厚度控制在2.9 nm、1.26 nm和0.9 nm，即使在如此超薄的层数下，多层薄膜的外延质量也很高。已经实现了非凡的光学特性，例如可见光范围内的等离子体共振以及强光学各向异性。此外，介电常数（ε'）的实部在不同波长范围内表现出相反的光学各向异性，即在350 nm-450 nm范围内ε∥'> 0，ε⊥'<0，而在更高波长下<0，ε⊥'>0，这是在多层系统中实现的新特性。
Multilayers with metal-dielectric stacks are considered as an effective approach to produce hyperbolic metamaterials (HMMs). However, fabricating ultrathin metal layers with high crystallinity for low-loss HMMs is very challenging. In this work, TiN has been applied as an alternative candidate to the noble metals, and TiN/MgO multilayers with varied numbers of layers and layer thicknesses have been designed. The microstructure study reveals that the thickness of TiN nanolayer is controlled as thin as 2.9 nm, 1.26 nm and 0.9 nm by varying the total number of layers, and the epitaxial quality of the multilayer films is high even with such ultrathin layers. Extraordinary optical properties have been achieved, such as plasmonic resonance in visible range, as well as strong optical anisotropy. In addition, the real part of dielectric permittivity (ε′) shows opposite optical anisotropy in different wavelength ranges, ie ε∥′> 0, ε⊥′< 0 in the range of 350 nm–450 nm, and< 0, ε⊥′> 0 under higher wavelength, which is a novel property realized in a multilayer system.