The investigation of focusing characteristic based on double Bowtie nano-lithography structure
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摘要:
Bowtie孔径结构已被广泛用于纳米直写光刻领域来获得超衍射聚焦光斑。然而,利用该结构获得的超衍射聚焦光斑呈椭圆形,影响了Bowtie结构的进一步应用。为了获得超衍射且圆形对称的聚焦光斑,本文提出了双Bowtie新型纳米光刻结构并利用Comsol软件仿真模拟了该结构的焦斑对称特性和电场增强特性。结果表明利用双Bowtie结构获得了圆形对称焦斑,并且出射面的电场强度得到了增强,是入射面电场强度的22倍。本文进一步将双Bowtie结构与金属/介质/金属结构相结合,使得局域增强后的透射光的传输距离(工作距)得到了显著延长。
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关键词:
- Bowtie孔径结构 /
- 纳米直写光刻 /
- 电场增强特性 /
- 金属/介质/金属结构
Abstract:Bowtie aperture has been widely applied in the realm of nanometer direct-writing lithography for obtaining focusing spots beyond the diffraction limit. However, the obtained spot is elliptic-shape for the Bowtie case, which impacts the applications of the Bowtie structure. Double Bowtie aperture, as a novel nano-lithography structure, is proposed to attain circle-symmetric focusing spots beyond diffraction limit. The results demonstrate that circle-symmetry spots can be obtained, and the electric field intensity of transmission light is 22 times of that of incidence. By combining the double Bowtie structure with metal-insulator-metal, the propagation length of the enhanced transmission light is obviously prolonged.
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Abstract: The Bowtie aperture structure is widely applied in the realm of nanometer direct-writing lithography for obtaining the focusing spots beyond the diffraction limit. However, the shape of spots obtained is elliptic under the Bowtie structure because the electric field is enhanced and located only in perpendicular to the aperture gap. This characteristic impacts the applications of Bowtie structure. To attain high-resolution and circle-symmetric focusing spots, the double Bowtie structure is proposed. The electric field is enhanced and located in both x and y directions due to the symmetry characteristic of the double Bowtie aperture. The free electrons are accumulated at four tips of the gap of the double Bowtie aperture, which stimulate the localized surface plasmas (LSPs) and develop the double-dipole oscillation mode. This characteristic attributes to obtain circle-symmetry spots and enhance the electric field intensity of transmission light. The simulated results demonstrate that the electric field intensity of transmission light is 22 times than that of incidence. However, the electric field intensity of transmission light decays in the form of exponential with the increasing of the working distance.
The electric field intensity of transmission light decays with exponential perpendicularly to the interface of metal/insulator but still propagates parallel to interface as evanescent wave. The transmission light is coupled into the interface of metal/insulator by this electric field generated by the evanescent wave, and which further stimulates surface plasmas (SPs). The silver, as a common waveguide material, can enhance and magnify the evanescent wave. We combine the double Bowtie structure with metal-insulator-metal structure. Although the electric field intensity still decays with exponential, the electric field intensity attained keeps 1 time as large as that of incidence light when the distance approaches to 50 nm. The propagation distance of light is obviously prolonged which benefits from the characteristic of the transmission enhancement of the upper silver and the characteristic of reflection of the bottom silver.
Therefore, the double Bowtie aperture has an advantage in obtaining high-resolution and circle-symmetry spots. Metal/insulator/metal structure combined with the double Bowtie aperture further attributes to prolong the transmission distance of light. This advantage facilitates the applications of Bowtie structure in nanometer direct-writing lithography technology.
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表 1 双Bowtie结构参数列表.
Table 1. Parameters of double Bowtie structure.
Parameters Parameter size/nm L 200 a 60 g 30 tM 30 -
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