Despite the exotic electromagnetic properties have been demonstrated in metamaterials to date, how to effectively adjust negative electromagnetic parameters remains a challenge. Tunable negative permittivity is essential for the metamaterials to satisfy a variety of practical applications, such as capacitor, microwave absorbing and shielding. Here, we fabricated a random metamaterial, carbon/silicon nitride (C/Si3N4) composite, using a feasible impregnation-pyrolysis method. The microstructure and dielectric property of the composites with different heat treatment temperatures (HTTs) and carbon contents were investigated. The amorphous carbon membrane adhered on the rod-like Si3N4 grains. The negative permittivity behavior combined with inductive character was obtained in the composites, which was attributed to the low frequency plasmonic state generated from the formative conducting carbon networks. The magnitude of negative permittivity is demonstrated to be successfully adjusted by controlling the HTT and carbon content. The result is in good agreement with the analysis of Drude model. Interestingly, a weakly negative permittivity behavior was observed in the measured frequency, showing small negative values of permittivity between −50 and −10, which was ascribed to a moderate carrier concentration provided by the carbon networks. This work provides an effective way to achieve the tunable and weakly negative permittivity in random metamaterials.

中文翻译：

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具有不同碳化温度的碳/氮化硅复合材料的可调和弱负介电常数

尽管迄今为止已经在超材料中证明了奇异的电磁特性，但如何有效地调整负电磁参数仍然是一个挑战。可调谐的负介电常数对于超材料满足各种实际应用（如电容器、微波吸收和屏蔽）至关重要。在这里，我们使用可行的浸渍-热解方法制造了一种随机超材料，碳/氮化硅 (C/Si3N4) 复合材料。研究了不同热处理温度（HTTs）和碳含量的复合材料的微观结构和介电性能。无定形碳膜粘附在棒状 Si3N4 晶粒上。在复合材料中获得了与电感特性相结合的负介电常数行为，这归因于形成性导电碳网络产生的低频等离子体状态。证明通过控制 HTT 和碳含量可以成功调整负介电常数的大小。结果与德鲁德模型的分析吻合较好。有趣的是，在测量频率中观察到微弱的负介电常数行为，显示介电常数在 -50 和 -10 之间的小负值，这归因于碳网络提供的中等载流子浓度。这项工作为在随机超材料中实现可调和弱负介电常数提供了一种有效的方法。结果与德鲁德模型的分析吻合较好。有趣的是，在测量频率中观察到微弱的负介电常数行为，显示介电常数在 -50 和 -10 之间的小负值，这归因于碳网络提供的中等载流子浓度。这项工作为在随机超材料中实现可调和弱负介电常数提供了一种有效的方法。结果与德鲁德模型的分析吻合较好。有趣的是，在测量频率中观察到微弱的负介电常数行为，显示介电常数在 -50 和 -10 之间的小负值，这归因于碳网络提供的中等载流子浓度。这项工作为在随机超材料中实现可调和弱负介电常数提供了一种有效的方法。