碳纳米管太赫兹波电磁特性研究

发布时间：2019-01-24 21:57

【摘要】：太赫兹波具有穿透、低能量、宽带及光谱分辨等独有的特性,赋予了其广泛的应用前景,并将给成像技术、光谱技术、通信技术及安全检测方面带来深远的影响。纳米材料的出现,给太赫兹技术的发展带来了新的契机。碳纳米管有着极具吸引力的固有属性,并得到了人们广泛的关注。碳纳米管的应用也从直流一直扩展到红外区域。但是,相比于微波及红外区域,碳纳米管在太赫兹区域的基础研究相对较少。本文对碳纳米管在太赫兹波的电磁传播特性进行了研究。基于等效介质的Maxwell-Garnett模型及Drude-Lorentz模型对单壁碳纳米管(single-walled carbon nanotubes,SWNTs)、双壁碳纳米管(double-walled carbon nanotubes,DWNTs)、氢杂化碳纳米管(H-deped CNTs)的电学属性进行建模及数值拟合。给出了碳纳米管的介电系数、介质损耗角正切及实电导率随频率变化的曲线。随后基于辅助差分方程的时域有限差分(ADE-FDTD)方法推导出碳纳米管的场及电流方程,并验证了方法的有效性。对不同厚度的碳纳米管的屏蔽效能进行了比较,结果表明碳纳米管在电磁屏蔽方面有潜在的应用。针对可应用于太赫兹器件的Si基片上的碳纳米管分层介质在太赫兹频段的传播进行了讨论,结果表明多反射及传输现象存在其中。碳纳米管的手性矢量决定了其结构,同时也决定了其很多的物理性质。本文通过对手性材料的分析,在Lorentz-Condon模型的基础上结合Drude-Lorentz模型,给出了用于FDTD计算的手性碳纳米管模型。用ADE-FDTD方法推导出手性碳纳米管的场方程迭代公式,验证了方法及计算结果的正确性,并对太赫兹波下手性碳纳米管的反射系数及传输系数进行了计算。通过对手性碳纳米管的分析,结果表明手性碳纳米管中存在旋光性及圆二色性,这将对以后的应用有一定的参考作用。最后本文用等效电路方法对手性介质进行了研究,给出了等效电路每单元部分的相位偏移和特征阻抗,并用ADS进行了验证。
[Abstract]:Terahertz wave has unique characteristics such as penetration, low energy, wide band and spectral resolution, which will have a great impact on imaging technology, spectral technology, communication technology and security detection. The appearance of nanomaterials brings new opportunities to the development of terahertz technology. Carbon nanotubes (CNTs) have attracted much attention because of their attractive properties. The application of carbon nanotubes also extends from DC to infrared region. However, compared with microwave and infrared regions, the basic research of carbon nanotubes in terahertz region is relatively small. The electromagnetic propagation characteristics of carbon nanotubes in terahertz wave are studied in this paper. On the basis of Maxwell-Garnett model and Drude-Lorentz model of equivalent medium, single-walled carbon nanotubes (single-walled carbon nanotubes,SWNTs), double-walled carbon nanotubes (double-walled carbon nanotubes,DWNTs), double walled carbon nanotubes (double-walled carbon nanotubes,DWNTs), The electrical properties of hydrogen hybrid carbon nanotubes (H-deped CNTs) were modeled and numerically fitted. The curves of dielectric coefficient, dielectric loss angle tangent and real conductivity with frequency are given. Then the field and current equations of carbon nanotubes are derived by the finite difference time domain (ADE-FDTD) method based on the auxiliary difference equation, and the validity of the method is verified. The shielding efficiency of carbon nanotubes with different thickness is compared. The results show that carbon nanotubes have potential applications in electromagnetic shielding. The propagation of layered carbon nanotubes (CNTs) on Si substrates which can be used in terahertz devices at terahertz band is discussed. The results show that the phenomenon of multi-reflection and transmission exists. The chiral vector of carbon nanotubes determines its structure and many physical properties. Based on the Lorentz-Condon model and Drude-Lorentz model, a chiral carbon nanotube (CNT) model for FDTD calculation is presented by the analysis of chiral materials. The iterative formula of field equation for chiral carbon nanotubes is derived by ADE-FDTD method, which verifies the correctness of the method and the calculation results. The reflection coefficient and transmission coefficient of terahertz wave chiral carbon nanotubes are calculated. Through the analysis of chiral carbon nanotubes, the results show that there are optical and circular dichroism in chiral carbon nanotubes, which will be useful for future applications. Finally, the chiral dielectric is studied by using the equivalent circuit method. The phase offset and characteristic impedance of each unit of the equivalent circuit are given and verified by ADS.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O441.6;TB383.1
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本文编号：2414899