低维硒化镉纳米材料物理性能预测

发布时间：2018-08-07 13:47

【摘要】：自石墨烯被发现以来,由于其独特的几何结构和优异的物理的性能,越来越受科研界的关注。本征结构的石墨烯带隙为零,科学家用物理方法施加应变使其能隙打开,或者通过化学方法掺杂其它原子来得到有带隙的石墨烯。还有通过改变石墨烯的维度,将两维的石墨烯剪切成一维的石墨带,来调节其电子结构,磁学和光学性质。由于二维纳米结构的独特性及石墨烯零带隙的问题,寻找及研究类似石墨烯的具有非零带隙的二维结构是现如今非常热门的一个研究课题。通过近几年科学家的不断努力,类石墨烯的二维及一维体系不断的被发现。其中包括过金渡属氧化物,II-VI族化合物,III-V族化合物等。CdSe作为II-VI族中一种重要的直接跃迁、较宽禁带的半导体材料,具有独特的物理和化学性能,并已成功应用于光放大器、太阳能电池、光电器件、生物荧光标记等。在过去几十年科研界致力寻找的二维结构的硒化镉纳米片已经在实验上通过溶胶的方法制备出1.4nm厚度。虽然实验已经制备出一定厚度Cd Se纳米片,但是对单层二维及一维Cd Se纳米片/纳米带的电子结构、光学和磁学性质的研究还比较少。本论文的主要研究内容如下:1.基于密度泛函理论的第一性原理,研究了二维硒化镉纳米片在均匀应变下对电子结构的影响,结果表明硒化镉纳米片的带隙随应变增加而减小。同时我们深入探讨了均匀应变对介电常数实部、虚部,光学常数中的折射系数、消光系数影响。研究中发现,介电常数虚部在应力增加的情况下峰值发生了红移,该红移现象同样发生在消光系数上。另外还研究了硒化镉纳米片的反射系数、吸收系数、能量损耗系数。2.基于密度泛函理论的第一性原理,研究了锯齿型和扶手型的硒化镉纳米带在不同宽度和在氢原子钝化与不钝化下的电子结构和磁学性质。研究发现扶手型硒化镉纳米带的带隙随宽度增加单调递减,表现为直接带隙半导体。而锯齿型硒化镉纳米带表现为具有磁性并表现为金属性质,其磁性在氢钝化下变为零。3.基于密度泛函理论的第一性原理,研究轴向应变对硒化镉纳米带的结构,电学,磁学性质的影响并探究了扶手型和锯齿型的稳定性。研究发现应变对硒化镉纳米带的几何结构,电子结构,磁学性质都很强的影响。通过结合能分析发现扶手型硒化镉纳米带比锯齿型硒化镉纳米带稳定。
[Abstract]:Since its discovery, graphene has attracted more and more attention due to its unique geometric structure and excellent physical properties. The band gap of graphene with intrinsic structure is zero. Scientists applied strain to open the band gap by physical method, or doped other atoms by chemical method to obtain graphene with band gap. By changing the dimension of graphene, two dimensional graphene is cut into one dimensional graphite band to adjust its electronic structure, magnetic and optical properties. Due to the uniqueness of two-dimensional nanostructures and the problem of zero-band gap of graphene, it is a very hot research topic to find and study two-dimensional structures with non-zero band gap similar to graphene. Through the continuous efforts of scientists in recent years, graphene-like two-dimensional and one-dimensional systems have been found. As an important direct transition and wide band gap semiconductor material in the II-VI family, CdSe has unique physical and chemical properties and has been successfully used in optical amplifiers. Solar cells, photovoltaic devices, bioluminescence labeling, etc. In the past few decades, the two-dimensional structure of cadmium selenide nanocrystalline has been experimentally prepared by sol method for the thickness of 1.4nm. Although a certain thickness of CD se nanocrystals has been prepared by experiments, the optical and magnetic properties of the monolayer and one-dimensional CD se nanocrystals / nanobelts have not been studied. The main contents of this thesis are as follows: 1. Based on the first principle of density functional theory, the effect of two-dimensional cadmium selenide nanoparticles on electronic structure under uniform strain is studied. The results show that the band gap of cadmium selenide nanoparticles decreases with the increase of strain. At the same time, the effect of uniform strain on the refraction coefficient and extinction coefficient in the real, imaginary and optical constants of dielectric constant is discussed. It is found that the peak value of the imaginary part of the dielectric constant is redshift when the stress increases, and the red shift also occurs in the extinction coefficient. In addition, the reflection coefficient, absorption coefficient and energy loss coefficient of cadmium selenide nanocrystals were studied. Based on the first principle of density functional theory, the electronic structure and magnetic properties of sawtooth and armrest cadmium selenide nanoribbons at different widths and under the condition of hydrogen atom passivation and non-passivation are studied. It is found that the band gap of the armrest type cadmium selenide nanoribbons decreases monotonously with the increase of the width, and appears to be a direct band gap semiconductor. However, the zigzag cadmium selenide nanoribbons exhibit magnetic properties and metal properties. The magnetic properties of the zigzag CDs nanoribbons change to zero. 3 under hydrogen passivation. Based on the first principle of density functional theory, the effects of axial strain on the structure, electrical and magnetic properties of cadmium selenide nanoribbons are studied, and the stability of armrest and sawtooth type is investigated. It is found that the strain has a strong effect on the geometrical structure, electronic structure and magnetic properties of cadmium selenide nanoribbons. Through the analysis of binding energy, it is found that the armrest cadmium selenide nanobelts are more stable than the serrated cadmium selenide nanoliths.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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