光控分子开关的电子输运性质研究

发布时间：2018-10-09 13:06

【摘要】：随着计算机的蓬勃发展,以传统硅半导体材料为基础的微电子器件由于受原理性的物理限制和生产工艺的限制,如今已经达到其发展的极限。广大科研工作者想到利用纳米尺度的分子来构造具有不同功能的分子器件来解决这种困境。随着越来越多的先进实验技术的发展,如扫描隧道显微镜(STM)、力学可控劈裂结、自组装单层膜和电迁移等,使得人们能够设计和测量不同功能的分子器件。通过对分子器件的大量研究,人们发现了很多与传统硅基半导体所构成的微电子器件类似的功能,例如分子整流、负微分电阻、存储功能和分子开关等。由于分子开关是未来分子电路和信息存储的基础,它的研究显得十分重要。分子开关是一种在不同触发条件下形成两种不同电导特性的双稳态的量子系统。常见的触发条件有STM、氧化还原反应、电场调控以及光等。在这所有的触发条件中,光刺激法是最容易被应用于未来,因为它容易集成,易于寻址开光响应速率快,且触发条件简单方便。在本文的工作中,我们通过基于密度泛函理论(DFT)和非平衡态格林函数理论(NEGF)相结合的第一性原理计算,研究了以金为电极,二噻吩乙烯、海因基衍生物和二氰基乙烯衍生物分别为中间散射区分子所构成的双电极系统的电子输运性质。其内容和结论有:(1)通过分析二噻吩乙烯两种不同结构的I-V曲线发现,通过闭合形式的电流远远大于其开放形式的电流,我们利用器件的投影自洽哈密顿分布以及不同偏压下的总透射情况阐述了开关行为的起源;(2)在讨论海因基衍生物的I-V曲线时,我们发现通过反式结构分子器件的电流要显著的高于顺式结构下的电流,呈现出明显的开关特性,此外,我们发现通过添加氟原子后,显著改善了这种开关的性能;(3)二氰基乙烯衍生物的I-V曲线显示了通过顺式结构的电流较高,该分子器件的顺反两种不同结构的电子输运性质的详细讨论是通过他们的透射谱以及投影自洽哈密顿量本征态。此外,顺式结构的分子器件在高偏压下出现了负微分电阻现象,我们通过其HOMO能级处的透射本征态解释了该现象。
[Abstract]:With the rapid development of computer, the microelectronic devices based on traditional silicon semiconductor materials have reached the limit of development due to the physical limitation of principle and the limitation of production technology. Many researchers think of using nanoscale molecules to construct molecular devices with different functions to solve this dilemma. With the development of more and more advanced experimental techniques, such as (STM), mechanical controlled splitting, self-assembled monolayer and electromigration, people can design and measure molecular devices with different functions. Through a lot of research on molecular devices, we have found many similar functions to traditional silicon based semiconductor devices, such as molecular rectification, negative differential resistance, memory function and molecular switch, etc. Because molecular switch is the basis of future molecular circuit and information storage, its research is very important. Molecular switch is a bistable quantum system with two different conductance characteristics under different trigger conditions. Common triggering conditions include STM, redox reaction, electric field regulation and light. Among all the trigger conditions, the optical stimulation method is the easiest to be applied in the future, because it is easy to integrate, to address the light response rate quickly, and the trigger condition is simple and convenient. In the work of this paper, based on density functional theory (DFT) and non-equilibrium Green's function theory (NEGF), we study the behavior of dithiophene with gold as electrode. The electron transport properties of a two-electrode system composed of Heinyl derivatives and dicyanoethylene derivatives are intermediate scattering region molecules, respectively. The main contents and conclusions are as follows: (1) by analyzing the I-V curves of two different structures of dithiophene and ethylene, it is found that the current in closed form is much larger than that in open form. The origin of switching behavior is explained by using the projective self-consistent Hamiltonian distribution of the device and the total transmission at different bias voltages. (2) when we discuss the I-V curves of Heinky derivatives, We found that the current of the transstructural molecular device was significantly higher than that of the cis structure, showing obvious switching characteristics. In addition, we found that after adding fluorine atoms, (3) the I-V curves of dicyanene derivatives show that the current passing through the cis structure is higher. The electron transport properties of the molecular devices with two different structures are discussed in detail through their transmission spectra and projective self-consistent Hamiltonian eigenstates. In addition, there is a negative differential resistance phenomenon in cis structure molecular devices at high bias voltage, which is explained by the transmission eigenstates at the HOMO level.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O561

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