二维层状材料的光学和光电性能调控

发布时间：2018-04-27 23:19

本文选题：石墨烯 + 二硫化钼　；参考：《东南大学》2016年博士论文

【摘要】：以石墨烯、二硫化钼为代表的二维层状材料由于其独特的性质和良好的应用前景已经引起了科学及工业界的广泛关注。石墨烯优异的电学、光学、热学和机械性质使其在电子、光电子、柔性器件、传感等多个领域有重要的应用前景。而以二硫化钼为代表的二维过渡金属硫属化合物不仅有着非常高的电学开关比,并且在可见光范围内也有着较强的吸收,是电子和光电器件的理想材料。研究发现,二维材料的性能受到层数、缺陷等因素的巨大影响。随着层数的增加,二硫化钼由直接带隙变为间接带隙,发光效率逐渐降低;另外,无论是何种方法制备的二维材料中都不可避免的存在缺陷,且显著影响材料的各种性质。因此,二维材料中层数和缺陷的探测以及调控是非常关键的问题。本论文主要通过层数控制和缺陷工程来实现二维层状材料光学和光电性能的调控。获得的主要结论如下:1.通过Ar等离子体轰击实现了二硫化钼、黑磷等二维层状材料的逐层减薄,使得多层二硫化钼从间接带隙变为单层的直接带隙。该方法没有在二硫化钼中引入多余的缺陷,且结合光刻等手段非常适合于大范围二维材料层数控制。2.通过高温退火或氧等离子体轰击实现了二硫化钼中缺陷的产生和缺陷位氧分子的化学吸附,使其荧光强度增加了数十倍。一方面氧分子的化学吸附对二硫化钼造成了强P型掺杂,使二硫化钼中的带电激子(trion)转化为中性激子(Exciton);另一方面当氧分子代替硫空位与钼成键时会形成局域化激子,降低非辐射复合的几率,从而引起荧光强度的大幅增强。3.利用氧等离子体处理实现了二硫化钼样品中缺陷的修复。通过低温荧光光谱分析了二硫化钼中的缺陷浓度,并发现缺陷的存在严重限制了二硫化钼样品的载流子迁移率。随后,通过氧等离子体处理对二硫化钼中缺陷进行了修复,从而有效提升其载流子迁移率。4.利用拉曼光谱分析石墨烯中的缺陷种类和含量,并通过缺陷来调控石墨烯的性质。发现在空气中对石墨烯进行热处理时会在其中引入缺陷,而缺陷形成的速度与浓度主要受退火温度、石墨烯层数和石墨烯晶粒尺寸影响。通过不同的等离子体处理在石墨烯中引入不同浓度和类型的缺陷,发现随着缺陷浓度的增加,石墨烯与金属纳米颗粒之间的相互作用逐渐减弱,证明了石墨烯与金属纳米颗粒之间存在电子转移并影响金属纳米结构的表面等离激元共振吸收。
[Abstract]:The two-dimensional layered materials, such as graphene and molybdenum disulfide, have attracted wide attention in the field of science and industry because of their unique properties and good application prospects. The excellent electrical, optical, thermal and mechanical properties of graphene have made it very promising in many fields, such as electron, optoelectronics, flexible devices, sensing and so on. Two The two dimensional transition metal sulfide, represented by molybdenum sulfide, not only has a very high electrical switching ratio, but also has strong absorption in the range of visible light. It is an ideal material for electronic and photoelectric devices. It is found that the properties of the two dimensional materials are affected by the number of layers, defects and other factors. With the increase of the number of layers, molybdenum disulfide From the direct band gap to the indirect band gap, the luminous efficiency is gradually reduced; in addition, there are unavoidable defects in the two dimensional materials prepared by any method, and the various properties of the materials are greatly affected. Therefore, the detection and control of the number of layers and defects in the two-dimensional material are the key problems. The main conclusions are as follows: 1. the layer by layer thinning of two dimensional layered materials such as molybdenum disulfide and black phosphorus can be thinned by Ar plasma bombardment, which makes the multilayer molybdenum disulfide change from the indirect band gap into single layer straight band gap. This method is not introduced in molybdenum disulfide. The superfluous defects, combined with photolithography, are very suitable for the large range two-dimensional material layer number control.2. to produce the defects in molybdenum disulfide by high temperature annealing or oxygen plasma bombardment, and the chemical adsorption of the oxygen molecules of the defects is increased by several times. On the one hand, the chemical adsorption of oxygen molecules to molybdenum disulfide is made. A strong P type doping has been made to convert charged exciton (Trion) into neutral exciton (Exciton) in molybdenum disulfide, on the other hand, when oxygen molecules replace sulfur vacancies with molybdenum, the localized exciton will be formed, which reduces the probability of non radiation recombination, resulting in a significant increase in fluorescence intensity by.3. using oxygen plasma treatment to achieve molybdenum disulfide samples. The defect concentration in the molybdenum disulfide is analyzed by the low temperature fluorescence spectrum, and the carrier mobility of molybdenum disulfide is seriously restricted by the existence of the defect. Then, the defects in molybdenum disulfide are repaired by the oxygen plasma treatment, and the carrier mobility.4. can be effectively enhanced by the Raman spectrum. The type and content of defects in graphene are analyzed and the properties of graphene are regulated by defects. It is found that the defects are introduced in the heat treatment of graphene in the air, and the velocity and concentration of the defects are mainly affected by the annealing temperature, the number of graphene and the grain size inch of graphene. The graphite is treated by different plasma in graphite. With the introduction of different concentrations and types of defects, it is found that the interaction between graphene and metal nanoparticles gradually decreases with the increase of the defect concentration. It is proved that the electron transfer between the graphene and the metal nanoparticles has an effect on the surface plasmon resonance absorption of the metal nanostructures.

【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O482

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