Titanium Oxynitride Thin Films with Tunable Double Epsilon-Near-Zero Behavior for Nanophotonic Applications
Titanium Oxynitride Thin Films with Tunable Double Epsilon-Near-Zero Behavior for Nanophotonic Applications
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DOI：
10.1021/acsami.7b07660
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发表时间：
2017-09-07
影响因子：
9.5
通讯作者：
Petrov, Peter K.
中科院分区：
文献类型：
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作者：
Braic, Laurentiu;Vasilantonakis, Nikolaos;Petrov, Peter K.
采用反应磁控溅射法制备了氮氧化钛（TiOxNy）薄膜。解释了它们的生长形成机制，并给出了它们的光学性质。当背景真空中的残余氧水平在5 nTorr至20 nTorr之间时生长的膜表现出双ε近零（2-ENZ）行为，ENZ 1和ENZ 2波长分别在700-850和1100-1350 nm光谱范围内可调。当本底真空中的残余氧水平高于2 × 10（-8）托时制造的样品表现出非金属行为，而当本底真空中的残余氧水平低于5 × 10（-9）托时沉积的层表现出金属4行为，具有单个ENZ值。双ENZ现象与背景真空中的残余氧水平有关，并且归因于薄膜中TiN和TiOxNy和TiOx相的混合物。在沉积期间改变氮的分压可进一步控制膜中TiN、TiOx和TiOxNy化合物的量，并因此调整屏蔽的等离子体波长。利用麦克斯韦加内特理论对TiO 2和TiN相的混合物形成的复合膜的椭圆偏振行为进行了很好的近似，表明双ENZ TiOxNy膜是由TiO 2基体中的TiN夹杂物形成的。这些氮氧化合物可以被认为是在可见光和近红外光谱范围内表现出双ENZ的新材料。具有ENZ性质的材料有利于设计增强的非线性光学响应、超颖表面和非互易行为。
Titanium oxynitride (TiOxNy) thin films are fabricated using reactive magnetron sputtering. The mechanism of their growth formation is explained, and their optical properties are presented. The films grown when the level of residual oxygen in the background vacuum was between 5 nTorr to 20 nTorr exhibit double epsilon-near Zero (2-ENZ) behavior with ENZ1 and ENZ2 wavelengths tunable in the 700-850 and 1100-1350 nm spectral ranges, respectively. Samples fabricated when the level of residual oxygen in the background vacuum was above 2 x 10(-8) Torr exhibit nonmetallic behavior, while the layers deposited when the level of residual oxygen in the background vacuum was below 5 X 10(-9) Torr show metallic 4 behavior with a single ENZ value. The double ENZ phenomenon is related to the level of residual oxygen in the background vacuum and is attributed to the mixture of TiN and TiOxNy and TiOx phases in the films. Varying the partial pressure of nitrogen during the deposition can further control the amount of TiN, TiOx, and TiOxNy compounds in the films and, therefore, tune the screened plasma wavelengths. A good approximation of the ellipsometric behavior is achieved with Maxwell Garnett theory for a composite film formed by a mixture of TiO2 and TiN phases suggesting that double ENZ TiOxNy films are formed by inclusions of TiN within a TiO2 matrix. These oxynitride compounds could be considered as new materials exhibiting double ENZ in the visible and near-IR spectral ranges. Materials with ENZ properties are advantageous for designing the enhanced nonlinear optical response, metasurfaces, and nonreciprocal behavior.