基于石墨烯的表面等离激元分子的研究

发布时间：2018-03-13 06:52

本文选题：石墨烯　切入点：表面等离激元分子　出处：《华侨大学》2017年硕士论文　论文类型：学位论文

【摘要】：类似于原子和分子系统,表面等离激元分子(Plasmonic Molecules,PMs)是由各个等离子体模式之间的相互作用,并且展现出独特的共有化行为的纳米结构。这些行为主要包括由于等离子体模式之间以及外部的激发导致的法诺(Fano)谐振、慢光(Slow Light)和电磁导致透明(Electromagnetically Induced Transparency,EIT)等。PMs由于具有Q值高、灵敏度高、结构设计灵活以及对环境改变具有敏感性的特点,因此在基础科学、信息处理、生物化学等领域有着重大的应用。传统的等离子体材料主要是贵金属,比如金和银,但是它们的结构一旦固定,其表面等离激元(Surface Plasmon Polartions,SPPs)的性质也就固定。基于金属的SPPs性质受到了限制的另一个原因是在金属表面传播的SPPs损耗较大,传播距离很短。石墨烯是由单层碳原子层构成的二维材料,由于其特殊的能带结构和优异的性能受到广泛的关注。本文利用石墨烯作为材料平台构建PMs,利用有限元方法(FEM)系统研究石墨烯PMs的本征光场性质以及远场消光光谱性质,具体研究内容如下:首先,计算基于石墨烯的双纳米盘PMs,分析了该PMs的TM2,1的模式特性随着盘间间距g、模式数和单个纳米盘的石墨烯化学势变化之间的关系。研究结果表明随着间距g的变化,成键态和反键态各自的两种模式频率差减小。随着模式数的增大,共振频率会向短波长偏移。随着石墨烯化学势的变化,其频率呈现出反交叉特性。并且研究了不同间距的关于x轴和y轴正对称的模式随着石墨烯化学势的变化关系,研究结果表明:当化学势在0.4eV左右,随着间距g的增大,共振频率的平台效应越明显,此时的Q值峰值有红移的现象。其次,本文利用数值方法解析了基于石墨烯的三纳米PMs,分析了该PMs的TM1,1模式特性随着顶角角度的变化规律及其散射特性。由于石墨烯具有可调谐性,因此我们分别计算了石墨烯化学势等于0.5eV和0.6eV的PMs模式特性和散射特性。研究结果表明随着顶角角度的增大,该PMs的对称性被破坏,简并模式开始分裂,相邻的两个模式之间的等离激元能量变化规律相反。利用等离激元能量谱图得到该PMs的散射特性。最后,改变三纳米盘PMs的对称性方式,分析该PMs的模式特性及其散射特性随着纳米盘的半径大小以及石墨烯化学势变化的变化规律。研究结果表明:随着纳米盘半径以及石墨烯化学势的变化,PMs的对称性遭到破坏,简并模式开始分裂,等离激元能量随着半径的减小或者化学势的增大而增大,Q值的变化规律与等离激元能量的变化规律一致。与变化顶角角度方法一致,利用等离激元能量谱图,得到该PMs的散射特性。
[Abstract]:Similar to atomic and molecular systems, the surface plasmonic molecules plasmonic moles (PMs) are interacted by various plasma modes. These behaviors are mainly due to the high Q value of Fano resonance, slow light light and electromagnetically transparent Induced transparent due to plasma modes and external excitation. Because of its high sensitivity, flexible structural design and sensitivity to environmental change, it has important applications in the fields of basic science, information processing, biochemistry, etc. Traditional plasma materials are mainly precious metals, such as gold and silver, However, once their structures are fixed, the properties of their surface Plasmon polarities are fixed. Another reason for the limitation of SPPs properties based on metals is that the SPPs loss propagating on the surface of metals is high. Graphene is a two-dimensional material consisting of a single layer of carbon atoms. Because of its special band structure and excellent properties, the graphene is used as the material platform to construct PMs.Finite-element method (FEM) is used to study the intrinsic light field properties and far-field extinction spectrum properties of graphene PMs. The specific contents of the study are as follows: first of all, The relationship between the mode characteristics of the PMs TM2O1 with the interdisc spacing, the number of modes and the chemical potential of graphene in a single nano-disk is calculated. The results show that the mode characteristics vary with the spacing g. The frequency difference between the bonding state and the antibonding state decreases. With the increase of the number of modes, the resonance frequency shifts to the short wavelength, and with the change of the chemical potential of graphene, In addition, the relationship between the positive symmetry modes of x axis and y axis with the chemical potential of graphene is studied. The results show that when the chemical potential is about 0.4 EV, the distance g increases with the increase of the chemical potential. The more obvious the platform effect of resonance frequency, the redshift phenomenon of Q peak value. Secondly, In this paper, three nanometre PMs based on graphene are analyzed by numerical method. The variation of TM1 / 1 mode characteristics and scattering characteristics of the PMs with angle of vertex are analyzed. Because graphene is tunable, Therefore, we have calculated the PMs mode characteristics and scattering characteristics of graphene chemical potential equal to 0.5eV and 0.6eV respectively. The results show that the symmetry of the PMs is destroyed with the increase of the angle of vertex, and the degenerate mode begins to split. The law of energy variation between the two adjacent modes is opposite. The scattering characteristics of the PMs are obtained by using the energy spectrum of the isophosphors. Finally, the symmetry of the PMs of the three nanometre disks is changed. The mode characteristics and scattering characteristics of the PMs are analyzed with the change of the radius of the nano-disk and the chemical potential of graphene. The results show that the symmetry of the PMs is destroyed with the change of the radius of the nano-disk and the chemical potential of graphene. The degenerate mode begins to split, and the variation of the equal-exciton energy increases with the decrease of the radius or the increase of the chemical potential, which is consistent with the variation of the isobaric energy, and is consistent with the method of changing the angle of the vertex. The scattering characteristics of the PMs are obtained by using the energy spectral diagram of the isotherm.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71;O485

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