轮烯分子器件的电子输运和光电性能的第一性原理研究

发布时间：2018-05-17 12:22

本文选题：轮烯分子 + 磁性电极　；参考：《太原理工大学》2017年硕士论文

【摘要】：随着电子学和电子器件微型化的不断发展,人们利用单分子或团簇,例如有机小分子和生物分子等构建各种功能的电子元器件已经成为当今的发展趋势。同时研究和测量这些分子器件的电学特性或光学特性也逐渐发展成为了一门独立的学科,即分子电子学。随着测量手段的不断发展和完善,分子电子学在实验和理论上都取得了实质性的进展。正是由于电输运性质对分子器件的性能起着至关重要的作用,因此研究分子器件的电输运机制具有非常重要的意义。有机分子由于其较弱的自旋轨道耦合效应和超精细相互作用被认为是构造分子器件最热门的材料之一。其中1,6-亚甲基[10]轮烯分子就是一种很有发展前景的有机分子,它拥有独特的几何结构和奇特的电子性质。该分子因为其稳定的π共轭电子结构和显著的芳香特性而备受关注,它也是实验研究的理想对象。但是到目前为止,对于该分子的电输运理论还少有研究。在本论文中,使用铁、钴或镍链作为电极并采用密度泛函理论和非平衡态格林函数相结合的计算方法,我们设计了几种以1,6-亚甲基[10]轮烯分子为基础的分子自旋电子器件并研究了其自旋相关的电输运性能和光电性能。在本文的第一章我们主要介绍了分子器件的研究现状和背景,第二章介绍了论文计算中所用到的理论知识,包括玻恩-奥本海默近似、哈特利-福克近似和密度泛函理论,在使用密度泛函理论计算时会涉及基函数的选取问题,我们会在第三章详细阐述。在第三章和第四章我们以过渡金属链为电极构建了两种不同结构的分子器件,并计算了其在电极磁性方向不同时的电流和光电流。我们的结果表明,这些器件具有非常突出的自旋过滤效应和巨磁阻效应,其中用镍金属链作电极时具有最佳的电输运性能,所以器件结构的不同对其输运性能的影响巨大。我们进一步研究了用镍金属链作为电极时器件的自旋极化的光电流表现,并且发现当直接用红外、可见或紫外线光照射器件时,可以生成自旋极化的光电流,但相应的微观机制是不同的。更重要的是,如果两个电极的磁化方向是反平行的,自旋方向不同的光电流会在空间上分开,从不同的电极流出,这个结论为同时生成两种自旋光电流提供了一种新的思路。
[Abstract]:With the development of electronics and miniaturization of electronic devices, it has become a trend to construct electronic components with various functions by using single molecule or cluster, such as organic small molecule and biological molecule. At the same time, the study and measurement of the electrical or optical properties of these molecular devices has gradually developed into an independent subject, that is, molecular electronics. With the continuous development and improvement of measurement methods, molecular electronics has made substantial progress in both experiment and theory. It is precisely because the electrical transport property plays a vital role in the performance of molecular devices, so it is of great significance to study the electrical transport mechanism of molecular devices. Organic molecules are considered as one of the most popular materials for structuring molecular devices because of their weak spin orbital coupling effect and hyperfine interaction. One of the most promising organic molecules is 1,1-methylene [10] rotorene, which has a unique geometric structure and unique electronic properties. Due to its stable 蟺-conjugated electronic structure and remarkable aromatic properties, the molecule is also an ideal subject for experimental study. So far, however, little research has been done on the theory of electrical transport of the molecule. In this paper, iron, cobalt or nickel chains are used as electrodes, and the density functional theory is combined with the non-equilibrium Green's function. We have designed several molecular spin electronic devices based on the 1 '6-methylene-[ 10] rotorene molecule, and studied their spin dependent electrical transport and optoelectronic properties. In the first chapter of this paper, we mainly introduce the research status and background of molecular devices. In the second chapter, we introduce the theoretical knowledge used in the calculation, including Boon-Oppenheimer approximation, Hartley-Fogg approximation and density functional theory. The selection of basis functions is involved in the calculation of density functional theory, which is discussed in chapter 3. In the third and fourth chapters, we have constructed two kinds of molecular devices with different structures using transition metal chains as electrodes, and calculated the current and photocurrent in different magnetic directions of the electrodes. Our results show that these devices have very prominent spin filtering effect and giant magnetoresistive effect, among which nickel metal chains have the best electrical transport performance when used as electrode, so the structure of the devices has a great influence on their transport performance. We further study the photocurrent behavior of spin polarization when nickel metal chain is used as the electrode, and we find that when the device is irradiated directly with infrared, visible or ultraviolet light, the spin polarization photocurrent can be generated. But the corresponding micro-mechanism is different. More importantly, if the magnetization direction of the two electrodes is antiparallel, the photocurrent with different spin directions will be separated in space and outflow from different electrodes. This conclusion provides a new idea for the generation of two kinds of spin photocurrent simultaneously.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O469

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