掺杂对锯齿型硅烯纳米带输运性质的影响

发布时间：2018-03-17 15:53

本文选题：锯齿型硅烯纳米带　切入点：自旋极化效应　出处：《苏州大学》2015年硕士论文　论文类型：学位论文

【摘要】：硅烯纳米带有着与石墨烯纳米带类似的几何结构和奇特的电学性质,在纳米器件中有着广泛的应用前景,近几年来掀起了广泛的研究热潮。本文采用电子密度泛函理论与非平衡格林函数相结合的理论研究方法,系统地研究了原子替代掺杂对锯齿型硅烯纳米带的自旋输运性质的影响。论文第一章讲述硅烯的研究背景以及硅烯纳米带的电子性质;第二章主要介绍了本论文所采用计算方法的理论基础,包括密度泛函理论和非平衡格林函数,并简单介绍了ATK计算软件包;第三章和第四章详细介绍并总结了本论文的主要研究工作和成果。主要内容和结论总结如下:(1)研究了单原子或双原子掺杂对锯齿型硅烯纳米带的电子输运性质的影响。根据纳米带两个边缘的自旋极化方向,我们分别研究了自旋极化反向的反铁磁态(AFM)和自旋极化同向的铁磁态(FM)硅烯纳米带。理论计算结果表明,在反铁磁态下,单原子(Al/P)掺杂使硅烯纳米带在费米能附近产生准束缚态,并在电导谱中以电导谷的形式呈现出来。我们可以通过掺杂不同类型的原子(Al/P原子),或者改变相同原子的掺杂位置,获得不同类型(P型或N型)的硅烯纳米带。当双原子掺杂时,由于杂质产生的准束缚态彼此之间产生相互作用,使系统的输运性质变得复杂。我们将两个杂质原子分别掺杂在纳米带的不同边缘,由于产生的两个准束缚态分别分布在费米能级的两边,体系的输运特性可以看作是由单原子掺杂表现出来的输运性质的简单叠加。完美的铁磁硅烯纳米带在费米能附近的能量范围内电子输运通道是完全导通的,具有金属性,而某些双原子掺杂体系的上自旋或下自旋电子的电导在费米能附近的能量区域出现了低谷,也就是说在费米能附近只允许一个自旋电子导通,出现了显著的自旋过滤效果。(2)研究了线掺杂碳原子对铁磁锯齿型硅烯纳米带的电子结构和输运性质的影响。根据两极输运系统的电极磁化方向不同,我们分别考虑了两电极磁化平行(parallel,P)和两电极磁化反平行(anti parallel,AP)两种构型。研究发现,当垂直于纳米带方向线掺杂碳原子时,与完美体系的电流电压特性曲线相比,掺杂体系的电流明显减少,并在特定的偏压范围内电流随电压的增加而减小呈现出负微分电阻效应(negative differential resistance,NDR)。当沿着纳米带方向线掺杂碳原子时,无论是改变掺杂位置还是纳米带的宽度,在电极磁化反平行构型下,都可以使两极体系在较宽的能量区域内产生很大的自旋极化输运,并且在费米面上引起了更为显著的近乎100%的自旋极化效果。这些奇特的研究结果将为制备诸如自旋过滤器等硅基纳米电子器件提供了理论支持和研究依据。
[Abstract]:Silicene nanocrystalline has the similar geometric structure and peculiar electrical properties as graphene nanobelts, so it has a wide application prospect in nanoscale devices. In recent years, there has been a widespread research boom. In this paper, the theory of the combination of the electron density functional theory and the non-equilibrium Green's function is used. The effects of atom substitution doping on the spin transport properties of zigzag silicene nanobelts are systematically studied. In chapter 1, the background and electronic properties of silyene nanoribbons are introduced. The second chapter mainly introduces the theoretical basis of the calculation method used in this paper, including density functional theory and non-equilibrium Green's function, and briefly introduces the ATK calculation software package. In chapter 3 and chapter 4th, the main work and achievements of this thesis are introduced and summarized in detail. The main contents and conclusions are summarized as follows: 1) the electronic transport properties of monoatomic or diatomic doped zigzag silicene nanobelts are investigated. According to the spin polarization direction of the two edges of the nanobelts, We have studied the antiferromagnetic (AFM) and the ferromagnetic (FMFM) nanoribbons with spin polarization in reverse direction, respectively. The theoretical calculation results show that in the antiferromagnetic state, Monatomic Al / P doping makes silicene nanobelts produce quasi bound states near Fermi energy and present in conductance spectra in the form of conductance valleys. We can change the doping position of the same atoms by doping different types of atoms to Alp atoms. Different types of Si (P or N) nanoribbons are obtained. When diatomic doping occurs, the quasi bound states produced by impurities interact with each other. The transport properties of the system are complicated by doping two impurity atoms at different edges of the nanobelts, because the resulting quasi bound states are distributed on both sides of the Fermi level, respectively. The transport properties of the system can be regarded as a simple superposition of the transport properties of monatomic doping. The perfect ferromagnetic silicene nanoribbons are completely conductive and have gold properties in the energy range near Fermi energy. In some diatomic doping systems, the conductance of upper or lower spin electrons is low in the energy region near Fermi energy, that is, only one spin electron is allowed to be conducted near Fermi energy. The effect of wire doped carbon atoms on the electronic structure and transport properties of ferromagnetic zigzag silicene nanobelts has been studied. According to the electrode magnetization direction of the two-pole transport system, the effect of linear doped carbon atoms on the electronic structure and transport properties of ferromagnetic zigzag silicene nanoribbons has been studied. We consider two configurations of magnetized parallel parallel (P) and anti parallel parallel (APs) of two electrodes respectively. It is found that when carbon atoms are doped perpendicular to the nanobelts, the current and voltage characteristic curves of the perfect system are compared with those of the perfect system. The current of the doped system decreases obviously, and the current decreases with the increase of voltage in a certain range of bias voltage. The negative differential resistance effect and negative differential resistance are observed when the carbon atoms are doped along the nanobelts. No matter the doping position or the width of the nanobelts are changed, the polarization transport of the two poles can be produced in a wide energy region under the antiparallel configuration of the electrode magnetization. Moreover, a more remarkable spin polarization effect of nearly 100% on Fermi surface has been obtained, which will provide theoretical support and research basis for the fabrication of silicon-based nanoelectronic devices such as spin filters.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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