硅锗核壳纳米线的带隙漂移和光吸收性质的应变调制

发布时间：2018-01-09 05:13

本文关键词：硅锗核壳纳米线的带隙漂移和光吸收性质的应变调制　出处：《湖南师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：作为微纳光电子器件领域中一类重要的结构单元,Si/Ge和Ge/Si核壳纳米线因其优异的物理和化学性质得到了科学家们的重点关注。核壳纳米线体系与相应的块体材料和单组元纳米线不同,它的壳层能使体系内载流子发生分离,容忍更多的无位错弹性形变,以及为体系表面势阱态提供有效钝化。此外,核、壳原子层之间由于界面失配和热胀系数的不同,体系将处于总能极小的自平衡态。因此,体系的性质将受到表面和界面的调制。从而,从理论的角度澄清界面之间的相互作用机理以及体系性质的尺寸和形状效应对核壳纳米线的制备和应用极为重要。半导体核壳纳米线结构的能带结构、带隙和光吸收系数是表征其电子学和光学性质的重要物理参量。目前的研究中,对此类问题的研究一般采用实验和计算的方法,而从原子层次的理论模型和相关理论机制的探索还比较缺乏,特别是对于尺寸和形状效应对体系能带结构和光吸收性质的调制机制还不清楚。因此,本论文中,基于我们所发展的原子键弛豫理论模型和连续介质力学理论,我们建立了尺度和形状依赖的核壳纳米线的带隙漂移和光吸收系数变化的理论模型。在此基础上,我们系统研究了Si/Ge和Ge/Si径向核壳纳米线的带隙漂移和光吸收系数变化的尺度和形状效应,取得的主要进展如下:(1)考虑不同截面形状(三角、四方、六边和圆形)的Si/Ge和Ge/Si核壳纳米线体系,我们建立了尺度和形状依赖的带隙漂移理论模型。通过研究发现:由于体系原子键长的自发收缩和界面晶格的错配的共同影响,核壳纳米线体系处于亚稳态,带隙相对于块体值发生蓝移;相比于其它截面形状的纳米线体系,三角形截面形状的体系具有最大的形变势;(2)研究了Si/Ge和Ge/Si核壳纳米线的光吸收系数的尺度和形状效应。结果表明:光吸收系数随着体系内核截面积和外延层厚度的增加而增大;在相同的情况下,四种截面形状的核壳纳米线的光吸收系数的大小关系满足以下关系:圆形六边四方三角。
[Abstract]:As an important structural unit in the field of micro-nano optoelectronic devices. Because of their excellent physical and chemical properties, Si/Ge and Ge/Si nanowires have attracted great attention. The core-shell nanowires are different from the corresponding bulk materials and monomorphic nanowires. Its shell can separate the carriers in the system, tolerate more dislocation free elastic deformation, and provide effective passivation for the potential well state on the surface of the system. In addition, the nucleus. Due to the difference of interface mismatch and thermal expansion coefficient between shell atoms, the system will be in a self-equilibrium state with minimal total energy. Therefore, the properties of the system will be modulated by the surface and interface. It is very important to clarify the interaction mechanism between interfaces and the size and shape effect of system properties for the preparation and application of core-shell nanowires. Bandgap and optical absorption coefficient are important physical parameters to characterize their electronic and optical properties. However, the theoretical models and related theoretical mechanisms at the atomic level are still lacking, especially the modulation mechanism of the size and shape effects on the band structure and optical absorption properties of the system. Based on the atomic bond relaxation model developed by us and the continuum mechanics theory, we have established the theoretical models of the band gap drift and the change of optical absorption coefficient of the core-shell nanowires depending on the scale and shape. We systematically study the scale and shape effects of band gap drift and optical absorption coefficient variation of Si/Ge and Ge/Si radial core-shell nanowires. The main progress is as follows: 1) the Si/Ge and Ge/Si core-shell nanowires with different cross-section shapes (triangle, tetragonal, hexagonal and circular) are considered. The theoretical model of scale and shape dependent band gap drift is established. It is found that the core-shell nanowire system is in metastable state due to the spontaneous contraction of the atomic bond length and the mismatch of the interface lattice. The band gap is blue shifted relative to the block value. Compared with other nanowire systems with cross-section shape, the system with triangular cross-section shape has the largest deformation potential. (2) the scale and shape effects of optical absorption coefficients of Si/Ge and Ge/Si core-shell nanowires are studied. The results show that the optical absorption coefficients increase with the increase of the core cross-sectional area and the thickness of the epitaxial layer. Under the same conditions, the optical absorption coefficients of four core-shell nanowires with different cross-section shapes are related to the following: circular hexagonal tetragonal triangle.
【学位授予单位】：湖南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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