表面功能化的石墨烯纳米带的电子结构和光学性质的研究

发布时间：2018-05-14 18:15

本文选题：石墨烯纳米带 + 第一性原理　；参考：《西南大学》2017年硕士论文

【摘要】：自2004年石墨烯(graphene)首次被英国曼彻斯特大学的科学家Novoselov和Geim从石墨中通过机械剥离的方法制备以来,它便以其特殊的二维结构、原子层厚度和优异的物理、化学性能,引起了科研人员的广泛关注。但由于石墨烯是零带隙的,它这种特殊的能带结构限制了它在光学领域的应用,比如它很不容易产生光致发光的现象。于是科学家尝试用多种方法来改造石墨烯,比如把石墨烯裁剪成宽度较窄的石墨烯纳米带(graphene nanoribbons,GNRs)。GNRs具有带隙,它是一种准一维的半导体材料,极大地扩展了石墨烯材料的应用领域。GNRs迅速成为了近年来的热门研究对象,并且也取得了快速地发展。科研人员一方面不断地改善着GNRs的制备方法,另一方面还积极地研究着它的电学性质、磁学性质和光学性质等。同时还尝试掺杂、缺陷等方法来修饰GNRs,不断地优化其性质,拓展其应用。GNRs是目前最受欢迎的半导体石墨烯材料之一,针对GNRs的可控方法对于未来的光学应用是非常有用的,但是针对表面功能化的GNRs影响还缺乏一些系统的研究,本文通过第一性原理计算,主要研究了表面官能团吸附对GNRs的电子结构和光学性质的影响,以及Stone-Wales缺陷和在缺陷上氢化对GNRs的电子结构和光学性质的影响。全文一共分为五章,本文的主要研究内容包括:第一章简单回顾了各种碳基纳米材料的发现历史以及研究现状,并重点介绍了GNRs的结构和性质。目前GNRs在实验上已经有多种制备方法被报道,GNRs也在场效应管、电子器件和传感器等领域展现出了其不可估量的潜在应用价值。第二章简单地介绍了密度泛函理论(density functional theory,DFT)的发展历史和基本结构框架,还介绍了Hohenberg-Kohn定理和Kohn-Sham方程,以及几个基于DFT的计算软件。本文中主要的软件有8)7)3,Quantum ESPRESSO和Yambo。第三章主要通过第一性原理计算研究了表面官能团吸附的扶手椅边缘型纳米带结构(W(n)-X armchair GNRs,W(n)-X AGNRs)的电子结构和光学性质,其中宽度指数n分别取值n=8,9和10,X表示官能团CH3,NH2,NO2和OH。我们发现大多数官能团扩大了W8和W9的带隙,并降低了W10的带隙。带隙的变化可以简单从成键特征来分析。在所有的W10-X结构,大部分激子波函数位于被官能团分割的大的区域。此外,W10-NO2具有光吸收强度高和激子结合能弱等特点,表明了这种结构具有潜在的光学应用,比如荧光发光和光伏等应用。第四章主要通过第一性原理计算研究了Stone-Wales缺陷和氢化的AGNRs的电子结构和光学性质。我们根据成键特征分析带隙的变化,发现SW缺陷增大了W8的带隙,并且减小了W9和W10的带隙。氢化增加了W8-和W9-SW的带隙,并且降低了W10-SW的带隙。W10-SW-H结构中的激子有明显的量子限域效应,即激子波函数的分布位于同一个边缘附近。此外,W10-SW和W10-SW-H结构之间的激子结合能差异仅为0.08 eV,具有未来应用于纳米级光学开关的可能。由于W9-SW较强的光吸收和较小的激子结合能,它具有应用于发光和光伏器件的潜在价值。第五章主要总结了本文的研究结果并对未来GNRs的应用进行了展望。我们的工作为GNRs的潜在应用提供了一些理论上的依据。
[Abstract]:Since Shi Moxi (graphene) was first prepared by Novoselov and Geim from the University of Manchester in 2004 by mechanical peeling from graphite, it has attracted extensive attention for its special two-dimensional structure, atomic layer thickness and excellent physical and chemical properties. However, graphene is zero band gap, it is a zero band gap. This special band structure restricts its application in the field of optics, such as it is not easy to produce photoluminescence. Scientists have tried to transform graphene in many ways, such as cutting graphene into a narrower graphene nanoribbons, GNRs.GNRs with a band gap, which is a quasi one dimension. Semiconductor materials have greatly expanded the application field of graphene materials, and.GNRs has rapidly become a hot research object in recent years, and has also achieved rapid development. On the one hand, researchers have continuously improved the preparation methods of GNRs. On the other hand, the electrical properties, magnetic properties and optical properties of it are also actively studied. We also try to modify GNRs, optimize its properties, optimize its properties, and expand its application.GNRs as one of the most popular semiconductor graphene materials. The controllable method for GNRs is very useful for future optical applications, but there is still a lack of systematic research on the effect of GNRs on surface functionalization. In the first principle, the effect of surface functional group adsorption on the electronic structure and optical properties of GNRs, and the effects of Stone-Wales defects and hydrogenated on the defects on the electronic structure and optical properties of GNRs are studied. The full text is divided into five chapters. The main contents of this paper include: the first chapter briefly reviews various carbon based nanoscale The discovery history and research status of the material, and the emphasis on the structure and properties of GNRs. At present, GNRs has been reported in the experiment, GNRs also shows its inestimable potential application value in field of field effect tubes, electronic devices and sensors. In the second chapter, the density functional theory (density) is briefly introduced. The development history and basic structure framework of functional theory, DFT, the Hohenberg-Kohn theorem and Kohn-Sham equation, and several DFT based computing software. The main software in this paper is 8) 7) 3, Quantum ESPRESSO and Yambo. third mainly study the edge type of the armchair adsorbed by the surface functional group by the first principle. The electronic structure and optical properties of W (n) -X armchair GNRs, W (n) -X AGNRs), in which the width exponent n values n=8,9 and 10 respectively. The W10-X structure, most of the exciton wave function is located in the large area divided by the functional group. In addition, W10-NO2 has the characteristics of high light absorption strength and weak binding energy of exciton. It shows that this structure has potential optical applications, such as fluorescent luminescence and photovoltaic applications. The fourth chapter is mainly to study the Stone-Wales deficiency through the first principle. The electronic structure and optical properties of the trapped and hydrogenated AGNRs are analyzed by the bond forming characteristics. It is found that the SW defect increases the band gap of W8 and reduces the band gap of W9 and W10. Hydrogenating increases the band gap of W8- and W9-SW, and reduces the quantum confinement effect of the exciton in the band gap.W10-SW-H structure of W10-SW, that is exciton. The distribution of wave functions is located near the same edge. In addition, the difference of exciton binding energy between W10-SW and W10-SW-H structures is only 0.08 eV, which has the potential to be applied to nanoscale optical switches in the future. Because of the strong absorption of W9-SW and the smaller exciton binding energy, it has the potential value for the application of light emitting and photovoltaic devices. The fifth chapters are mainly concerned. The research results in this paper are summarized and the application of GNRs in the future is prospected. Our work provides some theoretical basis for the potential application of GNRs.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O613.71

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