锯齿形硅烯纳米带电学性质的第一性原理研究

发布时间：2018-12-24 14:28

【摘要】：随着科学技术的不断革新,电子器件中材料的尺寸不断减小,当减少到纳米数量级时,电子波动性显著,材料出现奇特优异的性质。2004年,石墨烯(Grahpene)在实验室被成功的制备出,并发现其具有优异的性质,掀起了科学界的研究热潮。在过去的十年里,人们对石墨烯和石墨烯为基础的材料进行了广泛而深入的研究,包括富勒烯、碳纳米管、石墨烯纳米带等,并且一直努力的将该材料应用于电子器件中,但由于石墨烯为零带隙的半导体,在实际电子器件中不能直接的应用,因此结合现有的硅基技术使得人们对硅烯(Silicene)产生了浓厚的研究兴趣。硅烯是具有与石墨烯相似几何结构的新型二维材料,理论和实验都证明其可以稳定存在,并且能够很好的与现有的硅基技术相兼容,硅烯将有可能应用于现代电子器件中的最合适的材料之一。而将硅烯纳米材料应用于电子器件中对材料的裁剪及确定其电学特性就显得尤为重要。将硅烯或者硅纳米管进行裁剪,得到硅烯纳米带(Si NRs),按边缘手征性的不同将得到两种高对称结构的硅烯纳米带:锯齿型硅稀纳米带(Zigzag Silicene Nanoribbons,简称ZSi NRs)和扶手椅型硅稀纳米带(Armchair Silicene Nanoribbons,简称ASi NRs)。本文基于密度泛函理论(DFT),研究了锯齿形硅烯纳米带(ZSi NRs)的电学性质,主要讨论了不同边缘修饰对锯齿形硅烯纳米带的几何结构和电学性质的影响。我们选择了氢(H)、氟(F)、氢氧根(OH)和氧(O)对锯齿形硅烯纳米带进行边缘修饰,同时考虑了边缘电子间的交换关联使得自旋极化方向存在差异,锯齿形硅烯纳米带存在非磁态(Non-magnetic state,NM)、铁磁态(Ferromagnetic state,FM)和反铁磁态(Anti-ferromagnetic state,AFM)。我们首先基于密度泛函理论对边缘化学修饰后的锯齿形硅烯纳米带分别处于3种自旋磁态的几何结构进行优化,然后计算了能带、态密度和电荷密度,研究了不同化学元素边缘修饰对硅烯纳米带电学性质的影响。通过本论文的研究发现,硅烯具有与石墨烯类似的六角蜂窝状结构,与石墨烯不同的是硅烯两套三角格子不在同一平面内(即low-buckled六角蜂窝状结构),这与文献中的结构一致。边缘化学修饰对其几何结构并无太大的影响,受应力作用边缘的结构发生微小变化。然后对其能带结构图、态密度图和电荷密度图进行分析,结果表明边缘修饰以后的锯齿形硅烯纳米带存在局域边缘态(Localized edge states),并且发现自旋极化方向相反即反铁磁时费米(Fermi)能级附近的能带打开,出现能隙。本论文一共分为五章,第一章简要介绍了密度泛函理论;第二章介绍石墨烯、硅烯和硅烯纳米带的一些研究进展;第三章探讨了边缘修饰对锯齿形硅烯纳米带结构的影响;第四章研究了边缘修饰对锯齿形硅烯纳米带电学性质的影响;最后一章对本论文进行了一个总结。
[Abstract]:With the continuous innovation of science and technology, the size of materials in electronic devices is decreasing. When reduced to nanometer order of magnitude, electronic volatility is significant, and materials exhibit strange excellent properties. Graphene (Grahpene) was successfully prepared in laboratory and found to have excellent properties. In the past decade, graphene and graphene based materials have been extensively and deeply studied, including fullerene, carbon nanotubes, graphene nanoribbons, and have been used in electronic devices. However, because graphene is a zero-band gap semiconductor, it can not be directly applied in practical electronic devices. Therefore, combining with the existing silicon-based technology, people have a strong interest in the study of silicene (Silicene). Silene is a new two-dimensional material with similar geometric structure to graphene. It has been proved in theory and experiment that it can exist stably and is compatible with the existing silicon based technology. Silicene will probably be one of the most suitable materials for modern electronic devices. It is particularly important to apply silicene nanomaterials to the cutting of materials in electronic devices and to determine their electrical properties. Cutting silicene or silicon nanotubes to obtain silyene nanobelts (Si NRs),) according to the difference of edge chirality, two kinds of high symmetry silicene nanoribbons: sawtooth silicon thin nanobelts (Zigzag Silicene Nanoribbons,) will be obtained. ZSi NRs) and armchair (Armchair Silicene Nanoribbons, for ASi NRs). Based on density functional theory (DFT), the electrical properties of sawtooth silicene nanobelts (ZSi NRs) are studied. The effects of different edge modification on the geometric structure and electrical properties of sawtooth silicene nanoribbons are discussed. We have selected hydrogen (H), fluorine (F), hydroxide (OH) and oxygen (O) to modify the edge of the zigzag silicene nanobelts and consider the exchange correlation between the edge electrons which makes the spin polarization direction different. There are nonmagnetic (Non-magnetic state,NM), ferromagnetic (Ferromagnetic state,FM) and antiferromagnetic (Anti-ferromagnetic state,AFM) states in serrated silicene nanowires. Based on density functional theory (DFT), we first optimize the geometric structure of zigzag silicene nanobelts in three spin magnetic states, and then calculate the energy band, the density of states and the charge density. The effect of edge modification of different chemical elements on the charged properties of silicene nanocrystalline was studied. In this paper, we found that silicene has hexagonal honeycomb structure similar to graphene, unlike graphene, two sets of triangular lattice are not in the same plane (that is, low-buckled hexagonal honeycomb structure). This is consistent with the structure in the literature. The edge chemical modification has little effect on the geometric structure, and the structure of the edge is slightly changed by the stress. Then, the band structure, density of states and charge density are analyzed. The results show that the zigzag silicene nanobelts have localized edge (Localized edge states), after edge modification. It is also found that the energy band near the Fermi (Fermi) energy level is open in the opposite direction of spin polarization, that is, in the antiferromagnetic field, and the energy gap appears. This thesis is divided into five chapters. Chapter one introduces the density functional theory, the second chapter introduces the research progress of graphene, silicene and silicene nanobelts, the third chapter discusses the effect of edge modification on the structure of zigzag silicene nanoribbons. In chapter 4, the effect of edge modification on the charge-induced properties of zigzag silicene nanocrystalline is studied. In the last chapter, a summary of this thesis is given.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O613.72;TB383.1

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