基于二维材料碳化硅及硅烯纳米带的热自旋输运性质的研究

发布时间：2018-01-30 15:31

本文关键词：热自旋电子学碳化硅纳米带非平衡格林函数方法第一性原理密度泛函理论热自旋过滤效应热致负微分电阻效应自旋塞贝克效应硅烯自旋塞贝克二极管效应　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：基于自旋电子学及热电子学相结合的热自旋电子学在未来的的信息科学中有着广泛的应用,为未来开发出多功能材料和器件,特别是未来热电转换和低能耗器件的设计指明了新的方向,打破了传统电子学和自旋电子学的局限。本文采用基于密度泛函理论并结合非平衡态格林函数的方法,分别研究了锯齿型碳化硅及低翘曲结构硅烯纳米带构建的异质结器件的热自旋电流输运性质,具体开展了如下两个方面的工作:(1)我们设计了一个基于锯齿型边缘碳化硅纳米带异质结的两极器件,并研究了其温度差诱导的热自旋电流输运性质。该器件是由左电极的硅原子边缘用两个氢原子钝化和碳原子边缘用一个氢原子钝化,同时右电极的硅原子和碳原子边缘都用一个氢原子钝化,异质结的宽度由四个原子组成。通过计算它的热自旋电流输运的结果显示:热自旋极化电流随温度及温差变化曲线在超过一定的温度,大约300K处,它的热自旋向下的电流急剧增长,同时它的热自旋向上的电流几乎为零,表现了由温差诱导的完美的自旋过滤效应和效率极高的温控自旋开关效应。除此之外,热自旋电流随温度变化曲线还表现出热致负微分电阻效应并伴随有量子震荡现象。因此,我们预测锯齿型碳化硅纳米带可以用来设计出具有多功能的热激发自旋电子学器件。(2)我们构造了硅烯纳米带(N-ZSiNRs)异质结器件,研究了锯齿型边缘硅烯纳米带的热自旋输运性质。我们同样构造了一款左半无限长硅烯纳米带单边用一个氢原子钝化,右半无限长双边缘都由一个氢原子钝化的异质结。首先研究了(4-ZSi NR-H)/(4-ZSiNR-H2)器件的热电输运,研究结果表明通过源极和漏极间温差的调控,该器件的热自旋电流自旋向上和自旋向下的电流分别向着相反方向流动,净电荷流几乎为零,表现出了完美的自旋塞贝克效应。我们通过调控外加磁场实现巨磁阻效应。同时我们计算了不同宽度的硅烯纳米带(N-ZSiNR-H)/(N-ZSiNR-H2)(其中N表示垂直于ZSiNRs的armchair方向Si原子个数)器件的热电输运,研究结果显示偶数N的硅烯纳米带其自旋向上的电流和自旋向下的电流数量级相当,电流曲线几乎完全对称,并在某些温度处其总的电荷流为零,即只有纯净的自旋流,大大减少了器件的能量耗散,从而更有利于热激发自旋电子学的应用。而奇数N的纳米带破坏了热自旋流的对称性,具有较大的总电荷流,并且总的电荷流呈现出了丰富的物理性质。另外我们也能通过门电压来调控奇数宽度的硅烯纳米带,寻找到了一种可靠的调节实现纯净自旋流的方法,且通过门电压可以调节总的电荷流实现负微分电阻效应和整流效应。最后通过固定一端左电极温度,我们改变温差的方向,同时发现了自旋塞贝克二极管效应,从而为构造多功能高效的热电子学器件开辟了方向。
[Abstract]:Spintronics and thermal electronics based on the combination of thermal spintronics in the future of Information Science in a wide range of applications, for the future development of functional materials and devices, especially in the future design of thermoelectric conversion devices and low power consumption is the new direction, breaking the traditional electronics and spintronics based limitations. Using the density functional theory and combining the method of nonequilibrium Green's function based on the studied thermal spin current zigzag SiC heterojunction devices and low warpage of silicon and graphene nanoribbons on the transport properties of concrete developed the following two aspects: (1) we design a serrated edge silicon carbide nano heterojunction bipolar devices based on the belt, and the study of the differential thermal spin current induced transport properties. The device is composed of a silicon atom left edge electrode for two atoms of hydrogen passivation The carbon atoms and edges with a hydrogen atom and passivation, silicon atoms and carbon atoms of the right electrode edge with an atom of hydrogen passivation, the width of the heterojunction composed of four atoms. By calculating the thermal spin current its transport results show that thermal spin polarized current with temperature and temperature difference curve above a certain temperature, about 300K, its current thermal spin down rapidly, while current thermal spin it to almost zero, the temperature control switch by temperature induced spin effect perfect spin filter effect and high efficiency. In addition, the thermal spin current changes with temperature curve exhibit thermotropic negative differential resistance with quantum turbulence. Therefore, we predict the zigzag SiC nanobelts can be used to design the excitation of spintronics devices with multifunctional heat. (2) we construct silylenes Nanoribbons (N-ZSiNRs) heterojunction devices, studied the thermal spin zigzag edge graphene nanoribbons on silicon transport properties. We also constructed a left semi infinite graphene nanoribbons with a single silicon atoms of hydrogen passivation, right infinite double edge by the heterojunction of an atom of hydrogen passivation at first. Study (4-ZSi NR-H) / (4-ZSiNR-H2) device thermoelectric transport, the results show that by controlling the temperature difference between the source and drain current, the spin current of the device thermal spin up and spin down respectively in the opposite direction of flow, net charge flow is almost zero, showing the spin Seebeck effect perfect the external magnetic field. We realize the GMR effect through regulation. At the same time, we calculate the silylenes nano different width band (N-ZSiNR-H) / (N-ZSiNR-H2) (where N is perpendicular to the ZSiNRs direction armchair Si atomic number) device thermoelectric transport, research The current magnitude of silylenes nano showed even N with the spin current and spin down to the equivalent current curves are almost completely symmetrical, and in certain temperature the total charge current is zero, that is only the pure spin flow, greatly reducing the energy dissipation device, which is more conducive to the application of thermal excitation spintronics. Nano N with odd symmetry destroys the heat from cyclone, with large flow and total charge, total charge current exhibits rich physical properties. We can also silylenes nm by gate voltage to control the width of the odd belt, to find a reliable regulation implementation method of pure spin, and the gate voltage can be adjusted by the total charge current to achieve negative differential resistance and rectifying effect. Finally, the fixed end of the left electrode temperature difference, we change the direction, also found that the spin The Seebeck diode effect, thereby opening up direction for the thermal electronics structure of multifunction and high efficiency.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O613.72;TB383.1

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