Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures
Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures
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通过精确控制微观结构，实现银/二氧化硅随机超材料的双负特性
DOI：
10.34133/2019/1021368
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发表时间：
2019-01-01
期刊：
影响因子：
11
通讯作者：
Fan, Runhua
中科院分区：
文献类型：
--
作者：
Xie, Peitao;Zhang, Zidong;Fan, Runhua
随机超材料中负介电常数/负磁导率的产生机理目前还不清楚，由于其随机性，其微结构和电磁性能的精确控制也是一个挑战。本文采用自组装模板法将银引入多孔SiO2微球基体中，构建了无规超材料。银的分布受到SiO2微球空隙的限制，导致电渗流（从Hoping到Drude型导电）随银含量的增加而精确调节。负介电常数来源于银网络的类等离子体行为，其值和频散由洛伦兹型介电响应进一步调节。在此过程中，可以相应地调整ε近零（ENZ）的频率。银微网络中涡流的磁响应很好地解释了负磁导率。计算结果表明，负磁导率与ω 0. 5成线性关系，表现为弛豫型谱，与周期性超材料的"磁等离子体"不同。电磁场模拟结果表明，负介电常数材料和ENZ材料在厚度较薄（0.1mm）的情况下，仍具有40dB的强吸收和智能选频的优点，具有良好的电磁衰减和屏蔽性能。该工作为随机超材料中负介电常数和负磁导率的理论解释提供了清晰的物理图像，同时也为精确控制随机超材料的微结构提供了一种新的策略。
The mechanism of negative permittivity/permeability is still unclear in the random metamaterials, where the precise control of microstructure and electromagnetic properties is also a challenge due to its random characteristic. Here silver was introduced into porous SiO2 microsphere matrix by a self-assemble and template method to construct the random metamaterials. The distribution of silver was restricted among the interstices of SiO2 microspheres, which lead to the precise regulation of electrical percolation (from hoping to Drude-type conductivity) with increasing silver content. Negative permittivity came from the plasma-like behavior of silver network, and its value and frequency dispersion were further adjusted by Lorentz-type dielectric response. During this process, the frequency of epsilon-near-zero (ENZ) could be adjusted accordingly. Negative permeability was well explained by the magnetic response of eddy current in silver micronetwork. The calculation results indicated that negative permeability has a linear relation with ω0.5, showing a relaxation-type spectrum, different from the “magnetic plasma” of periodic metamaterials. Electromagnetic simulations demonstrated that negative permittivity materials and ENZ materials, with the advantage of enhanced absorption (40dB) and intelligent frequency selection even in a thin thickness (0.1 mm), could have potentials for electromagnetic attenuation and shielding. This work provides a clear physical image for the theoretical explanation of negative permittivity and negative permeability in random metamaterials, as well as a novel strategy to precisely control the microstructure of random metamaterials.