低维半导体纳米材料性能调控的理论研究

发布时间：2018-06-09 04:23

本文选题：低维半导体纳米材料 + 热导率　；参考：《上海师范大学》2017年硕士论文

【摘要】：随着纳米技术的不断发展,低维半导体纳米材料将对人们的生活产生重大影响。低维半导体纳米材料在电子、光学、热力学、机械以及化学上有着优异的特性,表现出了其所对应的块体材料所不具备的物理化学性质。对它们的功能性质的调制可以促进新型半导体器件的开发,从而推动技术的进步。理解和控制低维功能纳米材料的结构、物性以及结构--物性之间的关联,建立可控制备方法,对发展功能导向的新体系和新技术有着重要的指导意义。针对低维半导体纳米材料的物理性质及其调控的理论研究,本学位论文利用分子动力学模拟方法和基于密度泛函理论的第一性原理计算方法,分别以硒化镉纳米线、硒化镉纳米带以及单层砷结构为研究对象,探讨了这些体系在不同调控手段下,它们物理性质的变化,为今后低维半导体纳米材料的实际应用提供了重要的理论依据,主要研究内容和结果如下:(一)采用第一性原理计算方法研究了轴向应变条件下硒化镉纳米线的电子结构特性以及对其光学性质的变化。结果表明,应变作用下硒化镉纳米线的价带部分发生了价带顶竞争切换现象,且与纳米线孔径大小有一定关联。(二)采用分子动力学模拟方法研究了不同尺寸、应变、扭转角度以及温度对硒化镉纳米线热导率的影响。研究结果表明,压缩应变能更好地降低其热导率,使得热导率能在更大的范围内变化。(三)采用第一性原理计算方法研究了外加电场对扶手型硒化镉纳米带的能带结构的调制作用。通过施加横向电场,硒化镉纳米带的带隙随着场强的增大而逐渐减小,在一定场强下硒化镉纳米带从半导体转变到导体,其价带顶与导带底的电荷分布也随场强的增强而重新分布并向某一端靠拢。(四)采用第一性原理法研究了应变对单层砷结构的力学性质以及光学性质的影响。单层砷结构在横向应变条件下其面内具有正泊松比,且各向异性,而在面外x方向的拉伸引起了z方向的膨胀,具有负泊松比,数值大于黑磷的负泊松比。同时,应变也引起了单层砷结构光学性质的变化,且呈现出了各向异性行为。
[Abstract]:With the development of nanotechnology, low-dimensional semiconductor nanomaterials will have a great impact on people's lives. Low-dimensional semiconductor nanomaterials have excellent properties in electronics, optics, thermodynamics, mechanics and chemistry, showing physical and chemical properties that their corresponding bulk materials do not have. Modulation of their functional properties can promote the development of new semiconductor devices and promote the progress of technology. Understanding and controlling the relationship between structure, physical properties and structure-physical properties of low-dimensional functional nanomaterials and establishing controllable preparation methods are of great significance for the development of new functional oriented systems and new technologies. Based on the theoretical study of physical properties and regulation of low-dimensional semiconductor nanomaterials, this dissertation uses molecular dynamics simulation method and first-principle calculation method based on density functional theory, respectively, using cadmium selenide nanowires. The structure of cadmium selenide nanoribbons and monolayers as well as arsenic monolayers were studied. The changes of their physical properties under different control methods were discussed, which provided an important theoretical basis for the practical application of low-dimensional semiconductor nanomaterials in the future. The main contents and results are as follows: (1) the electronic structure and optical properties of cadmium selenide nanowires under axial strain are studied by first principle method. The results show that the valence band switching phenomenon occurs in the valence band of cadmium selenide nanowires under strain, which is related to the pore size of the nanowires. (2) the effects of different sizes, strain, torsion angle and temperature on the thermal conductivity of cadmium selenide nanowires were studied by molecular dynamics simulation. The results show that the compression strain can reduce the thermal conductivity more effectively and make the thermal conductivity change in a larger range. (3) the modulation effect of applied electric field on the band structure of the armrest type cadmium selenide nanoribbons has been studied by using the first-principle calculation method. By applying a transverse electric field, the band gap of cadmium selenide nanobelts decreases with the increase of the field strength. At a certain field strength, the band gap of CD _ 2See nanobelts changes from semiconductor to conductor. The charge distribution at the top and bottom of the valence band redistributes with the increase of the field strength and draws closer to one end. (4) the influence of strain on the mechanical and optical properties of arsenic monolayer is studied by first principle method. The monolayer arsenic structure has a positive Poisson's ratio in the plane and anisotropy under transverse strain, while the stretching in the off-plane x direction leads to the expansion in the z direction, which has a negative Poisson's ratio, which is larger than the negative Poisson's ratio of black phosphorus. At the same time, the strain also caused the change of optical properties of arsenic monolayer structure, and showed anisotropic behavior.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN304;TB383.1

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