类石墨烯二维异质结构和单原子纳米链的电子输运性质

发布时间：2018-01-05 23:12

  本文关键词：类石墨烯二维异质结构和单原子纳米链的电子输运性质　出处：《山东大学》2017年博士论文　论文类型：学位论文

  更多相关文章： 异质结构 二维纳米材料 纳米链 电子输运 第一性原理

【摘要】：随着电路的集成化和电子元器件的小型化,纳米电子器件以其独特的性能越来越受到人们的关注。纳米异质结构是由至少两种不同的纳米材料组成,因其可以改进材料的性能从而满足实际应用需求,成为了当下研究的热点。目前,随着对纳米电子器件研究的深入,对其电子输运性质等内在机理的研究成为了人们关注的焦点。本论文利用利用第一性原理和非平衡格林函数的方法,研究了二维纳米异质结构和单原子纳米链的电子输运性质,揭示了如何通过掺杂和构造异质结构改变电子输运性质。全文的主要内容如下:(1)研究了掺杂三角形氮化硼石墨烯纳米带的自旋磁性。发现在不考虑自旋极化时,器件是金属性,而且随着三角形氮化硼纳米片尺寸的增大,其电子输运能力逐渐被抑制。考虑自旋极化后,器件转变为半导体特性,并且通过改变三角形氮化硼纳米片尺寸的大小,可以调控其自旋极化性质。重要的是,在T_B_15N_21中,出现了双磁性半导体性质,并且拥有很高的电子输运能力和接近100%的自旋过滤效率,而具有相同氮化硼原子数的矩形氮化硼R_3BNNR没有出现双磁性半导体性质,并且其电子输运能力被限制。与掺杂三角形氮化硼的石墨烯纳米带类似,三角形空位的V_B(15)N(21)也出现了双磁性半导体性质,并且也有很高的自旋过滤效率,但是其电子输运能力和稳定性都不如掺杂三角形氮化硼的T_B_(15)N_(21)。(2)构造了平行和垂直排列拼接的MoS_2NRs和WS_2NR_s异质结构。研究了这些异质结构的电子输运性质,发现所有的异质结构都表现出直接带隙半导体的特性,这意味着这些异质结构可以用于光电子器件。随着WS_2NR_s纳米带的增加,带隙微弱较小,导致了电流的快速增长和更高的峰值电流。此外,随着WS_2NR_s纳米带的增加,对于M(na)双电极器件,负微分电阻效应得到一定提高,而M(nz)双电极器件的负微分电阻效应的变化却表现出相反的趋势,但是电流增长更快,峰值电流更高,这说明垂直拼接的M(na)双电极器件在逻辑电路中有更好的应用前景。特别指出的是,钨原子在边界的M(edge)双电极器件不仅有很显著的负微分电阻效应,而且在低压区还有很高的峰值电流,其逻辑电路的应用性能最好。(3)研究了扶手椅型和锯齿型MoS_2NRs/WS_2NR_s异质结构的电子输运性质。我们发现所有扶手椅型MoS_2NRs/WS_2NR_s异质结构都表现出电流的整流效应,意味着这类结构可以应用于pn结分子整流器。随着异质结构中WS_2纳米带长度的增加,整流效应被抑制,这是由于在正压区电子透射峰下降导致的。此外,在正压区和负压区都观察到了负微分电阻效应,并且可以通过改变WS_2纳米带长度来调节负微分电阻效应的强弱。对于所有锯齿型MoS_2NRs/WS_2NR_s异质结构,除了负微分电阻效应,也观察到了自旋过滤效应,意味着这类异质结构可以应用于自旋电子器件。随着异质结构中WS_2纳米带长度的增加,自旋过滤效率升高,zMoS2-5zWS_2NR_s达到60%。当连接WS_2纳米带电极时,无论是否考虑自旋极化,MoS_2NRs/WS_2NR_s异质结构都表现出比较好的电子输运性质,如高的自旋过滤效率和较好的负微分电阻效应。(4)研究了碳纳米链,氮化硼纳米链,和纳米链异质结构的电子输运性质。我们发现所有的单原子链都表现出奇偶效应,而且随着长度的增加,输运性质被抑制。在偶数的单原子链中,除了纯的碳链外,都出现了电流的整流效应,我们发现整流效应是由非对称的电子结构引起的。此外,倾斜的碳链几乎对输运性质没有影响,然而双碳链的传输能力可以提高两倍。当考虑自旋极化后,所有的结构都是磁性半导体,而且自旋过滤效应呈现奇偶性。重要的是,链通道的态密度决定了电子透射率谱和器件的电流电压特性曲线。电流电压曲线的变化,可以很好地用平衡态下的电子透射率谱解释,费米能级附近和远离费米能级的透射峰很好地对应了低压区和高压区的电流。此外,对于单原子链异质结构,通过改变碳原子和氮化硼的原子个数,其电学特性可以有效地调节。CnBNm异质结构电流的整流效应彼此之间类似,表现出正向和反向的整流现象,而且随着碳原子数的增加,电流的传输能力提升一倍。特别是当碳原子在链通道和石墨烯纳米带连接处时,其电子输运能力得到很大地提高,如电流的传输能力和整流效应。然而当考虑自旋极化后,碳链在一侧时的自旋过滤效应更好。本文的研究内容对于深入理解二维纳米异质结构和单原子纳米链的电子输运性质具有重要意义,为设计和开发高性能的纳米电子器件提供了理论指导。
[Abstract]:With the miniaturization of integrated circuit and electronic components, nano electronic devices with its unique performance more and more attention. The nano heterostructure is composed of at least two different nano materials, because of its performance can be improved materials to meet the actual application requirements, has become the focus of current research. At present, with the study of nano electronic devices in-depth research on the electronic transport properties of the internal mechanism has become the focus of attention. This paper use the first principle method and non equilibrium Green function, two Vinami heterostructures and single atomic chain of nano electron transport properties, reveals how by doping and the structure of heterogeneous structure change electron transport properties. The main contents of this paper are as follows: (1) study the triangle doped boron nitride graphene nanoribbons. Without considering the spin magnetic found Spin polarization, device is a metal, and with the increasing size of the triangle of boron nitride, was gradually suppressed its ability to transport electrons. Considering spin polarization, the device into the semiconductor properties, and by changing the triangle of boron nitride size, can control the spin polarization properties. It is important in the in T_B_15N_21, the double magnetic semiconductor properties, and has very high filtration efficiency of the electron spin transport capacity and close to 100%, while R_3BNNR has the same rectangular boron nitride boron nitride atoms do not appear double magnetic semiconductor properties, and its electronic transport capacity is limited. Similar to graphene nano doped boron nitride triangle with triangle vacancy of V_B (15) N (21) also appeared double magnetic semiconductor properties, and also has a very high spin filter efficiency, but its electronic transport ability and stability As the doped boron nitride triangle T_B_ (15) N_ (21). (2) constructed parallel and vertical splicing of the MoS_2NRs and WS_2NR_s heterostructure. Study the electron transport properties of these heterostructures, found all heterostructures have shown the characteristics of direct band gap semiconductor, which means that the heterostructure can be used for optoelectronic devices. With the increase of WS_2NR_s nanobelts, weak band gap is smaller, leading to a rapid growth of current and higher peak current. In addition, with the increase of WS_2NR_s nanobelts, for M (NA) dual electrode device, negative differential resistance effect is greatly increased, and the M (NZ) negative change differential resistance effect of double electrode devices but showed the opposite trend, but the current growth faster, higher peak currents, which shows that the vertical mosaic M (NA) have better application prospect in logic circuit of double electrode device in particular, Tungsten atoms at the boundary of the M (edge) dual electrode device not only has negative differential resistance effect is significant, but also in the area of low pressure and high peak current, the logic circuit (3). The best application performance of the electronic armchair and zigzag type MoS_2NRs/WS_2NR_s heterostructures we found all transport properties. Armchair MoS_2NRs/WS_2NR_s heterostructures exhibit rectifying effect of current, means of this kind of structure can be applied to the PN node. With the increase of molecular rectifiers WS_2 heterostructure nanoribbons length, rectifying effect is suppressed, which is due to the positive pressure area of electronic transmission peaks decrease. In addition, in the area of positive pressure and the negative pressure region is observed in the negative differential resistance, and can be changed by WS_2 nano belt length to adjust the negative differential resistance strength. For all the zigzag MoS_2NRs/WS_2NR_s heterostructure, in addition to the negative micro Electrical effect, also observed the spin filtering effect, means that the heterogeneous structure can be used in spin electronic devices. With the increase of WS_2 heterostructure nanoribbons length, higher spin filtering efficiency, zMoS2-5zWS_2NR_s can reach 60%. when connecting WS_2 nanoband electrode, whether or not to consider the spin polarization, MoS_2NRs/WS_2NR_s heterostructures exhibit good electron transport properties, such as high spin filter efficiency and good effect. The negative differential resistance (4) carbon nano chain was studied, boron nitride nano electronic and nano chain chain, the heterogeneous structure of transport properties. We found all the single atomic chain have shown parity effect, and with the length of the increase transport properties were restrained. Even in single atomic chain, in addition to the pure carbon chain, there are current rectification effect, we found that the rectification effect is caused by the electronic structure of asymmetric lead The influence of tilt. In addition, the transport properties of carbon chain almost no, however the transmission ability of double carbon chain can be increased by two times. When considering spin polarization, all structures are magnetic semiconductors, and presents the parity of the spin filtering effect. It is essential that the chain channel determines the current density of states voltage characteristic curve of transmission spectrum and electronic devices. The change of current voltage curve, can explain the electronic transmission spectrum under equilibrium well, the Fermi level near and far from the Fermi level of the transmission peaks correspond well to the current low pressure area and high pressure area. In addition, the single atomic chain heterostructure, through the number of atoms change the carbon atoms and boron nitride, similar between rectifying effect can effectively regulate the electrical properties of.CnBNm heterojunction current to each other, showing rectification phenomenon of forward and reverse, and with the number of carbon atoms. Plus, the current transmission capacity doubled. Especially when the carbon atoms in the chain connecting channel and graphene nano, has greatly improved its ability to transport electrons, such as the current transmission capacity and rectifying effect. However, when considering spin polarization, spin filtering effect of carbon chain on the side of the better. The research content of this paper has important significance for understanding the electronic two-dimensional nano heterostructures and single atom nano chain transport properties, to provide theoretical guidance for the design and development of nano electronic devices with high performance.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1
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本文编号：1385257