磁性酞菁锰分子在半金属表面的STM研究

发布时间：2018-01-16 10:16

本文关键词：磁性酞菁锰分子在半金属表面的STM研究　出处：《西南大学》2015年硕士论文　论文类型：学位论文

【摘要】：在纳米技术领域中,分子可作为自下而上构建功能性纳米结构的重要基石。基于先进的化学合成技术,人们利用分子的新奇性质和分子纳米结构来筑造许多可控且灵活的分子器件。因此,功能性分子无疑会成为制备具有多功能的纳米设备的基本材料之一。金属表面分子吸附体系正好可用于研究分子在表面的结构和性质,为进一步构筑高功能分子纳米结构提供先决条件。同时,对分子在金属表面的吸附体系的研究也有助于人们认识表面物理、化学、生物现象。目前,人们利用具有原子分辨的表征和操纵能力的扫描隧道显微镜(STM),并结合扫描隧道谱学(STS)及其他分析手段,在研究单分子吸附体系中已经取得了丰硕的成果。当然,STM也在金属表面分子吸附体系研究中展现出独特的优势。在本论文中,我们利用超高真空低温扫描隧道显微镜研究了吸附在半金属Bi(111)表面的磁性酞菁锰分子体系。第一章介绍了纳米科技的前沿知识和国际纳米技术发展水平。各种新奇的低维材料的出现及其特殊性质为纳米科技的发展不断注入新的活力。其次,介绍了低维材料的制备及其表征方法,低维材料制备可以在原子级或分子级可控,而且可以原位生长和表征样品,使得测量结果更加准确,进而获得样品的本征特性。其中我们侧重阐述了薄膜的成核与生长过程机制理论描述。最后,结合研究课题的内容介绍了目前扫描隧道显微镜在研究金属表面分子体系中取得的成果,如表面分子运动实时监控、表面分子操纵等等。第二章主要介绍了本实验室使用的超高真空低温强磁场STM系统USM1500。主要介绍了实验中所涉及的超高真空技术、分子束外延技术、低温强磁场技术以及STM的基本结构与工作原理。详细地介绍了先进的扫描隧道谱技术,该技术能够表征样品表面局域的电子态密度,并且能够测量电子态密度分别以空间和能量为变量的分布。利用扫描隧道显微镜微分电导谱和成像技术能够直接研究分子结构、分子轨道及分子衬底之间的相互作用。第三章介绍了我们利用低温STM研究了半金属Bi(111)表面上单个酞菁锰分子的吸附行为和转动特性。通过高分辨STM图发现,在液氮温度(78 K)下单个酞菁锰分子呈六角形形状。利用STM操纵技术实现了对单个酞菁锰分子的制动,并通过对单分子的高低起伏和吸附构型分析,确定分子在Bi(111)表面做非连续的中心转动。这种单分子转动是三种相对稳定的吸附构型交替变化的结果。结合STM的I-t谱技术,进一步验证了单个MnPc分子的三种分子吸附构型的存在。利用洛伦兹线形拟合对实验统计值拟合分析,得到单个转动的MnPc分子在Bi(111)表面的三种不同的吸附构型出现的概率及其相对能量,从而确定出最稳定的吸附构型。在第四章中,我们主要利用LT-STM的微分电导成像技术对包含有磁性酞菁锰分子的区域进行成像,观察表面局域电子态密度的分布。通过快速傅里叶变化(FFT)技术,我们发现在4.6 K和78 K下单分子磁体对Bi(111)表面电子态密度的散射模式中存在背散射,并且在4.6 K下分子对表面态的散射模式依赖于分子在Bi(111)表面上的吸附方向,从而证明MnPc分子的自旋磁矩可以打破Bi(111)表面的时间反演对称性的保护。
[Abstract]:In the field of nanotechnology, molecular can be used as an important cornerstone of bottom-up construction of functional nanostructures. The chemical synthesis technology based on advanced people use novel properties and molecular structure of nano molecular molecular devices to build many controllable and flexible. Therefore, functional molecules will undoubtedly become one of the preparation of multifunctional nano device the basic molecular material. The metal surface adsorption system just can be used to study the molecular structure and properties of the surface, providing a precondition for further fabrication of high functional nanostructures. At the same time, the study of adsorption on the metal surface of the molecular system also helps people understand the surface physical, chemical and biological phenomena. At present, scanning tunneling people with atomic resolution microscopy characterization and manipulation ability (STM), and scanning tunneling spectroscopy (STS) and other analytical methods in the study of single molecules Have achieved fruitful results in adsorption system. Of course, STM also in the study of molecular metal surface adsorption system shows unique advantages. In this paper, we use the ultra high vacuum low temperature scanning tunneling microscope was studied in semi metal Bi (111) surface magnetic molecular KCeO2MnPcX phthalein system. The first chapter introduces nanometer science and technology knowledge and international nanotechnology development. A variety of novel low dimensional materials have special properties and for the development of nano science and technology continue to inject new vitality. Secondly, introduces the method of preparation and characterization of low dimensional materials, low dimensional materials can be prepared at the atomic or molecular level controlled. But also the growth and characterization of in situ samples, the measurement result is more accurate, the intrinsic properties of obtained samples. We focuses on the thin film theory of nucleation and growth process mechanism described. Finally, node Research topics are introduced in scanning tunneling microscopy study of metal surface molecular system achievements, such as surface molecular motion real-time monitoring, surface molecular manipulation etc. the second chapter mainly introduces the laboratory using ultra high vacuum low temperature and high magnetic field STM system USM1500. is introduced to the ultra high vacuum technology experiment in molecular beam epitaxy, the basic structure and working principle of low temperature and high magnetic field technology and STM. This paper introduces the advanced scanning tunneling spectrum technology, the technology can characterize the local surface electron density, and can measure the density of electronic states respectively in space and energy for the distribution of variable differential by scanning tunneling microscopy. The conductance spectrum and imaging technology can directly study the molecular structure, the interaction between the molecular orbitals and the substrate. The third chapter introduces the Low temperature STM of semi metal Bi (111) adsorption behavior on the surface of a single molecule Manganese Phthalocyanine and rotational characteristics. Through the map found high resolution STM, at the temperature of liquid nitrogen (78 K) under a hexagonal shape. Manganese Phthalocyanine molecular manipulation technology to achieve the braking of a single molecule of Manganese Phthalocyanine by STM, and through the single the ups and downs of molecular adsorption and configuration analysis, determine the molecules on Bi (111) non continuous rotation center surface. This is the three single molecular rotation adsorption configuration relatively stable alternating results. Combined with the STM I-t spectrum technology, further validation of the three kinds of molecular adsorption configuration of single MnPc molecules in value exist. Fitting analysis of experimental statistics using Lorenz linear fitting, a single rotation of the MnPc molecules on Bi (111) the probability of occurrence of three different adsorption configurations on the surface and the relative energy, so as to determine the most stable adsorption configurations. In the fourth chapter, we mainly use the differential conductance imaging LT-STM for imaging magnetic Manganese Phthalocyanine molecular region to contain, to investigate the distribution of the local surface density of electronic states. By fast Fourier transform (FFT) technique, we found that at 4.6 K and 78 K single molecular magnets of Bi (111) backscattering scattering the surface of the electronic density of States, and the molecular scattering mode at 4.6 K on the surface states depend on molecules on Bi (111) adsorption on the surface so as to prove the direction, the spin magnetic moment of MnPc molecule can break the Bi (111) surface protection time reversal symmetry.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O561

【共引文献】