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所在平台: Coursera |
课程主页: https://www.coursera.org/learn/microscopy
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课程名称：材料科学中的透射电子显微镜 课程概述：本课程全面介绍材料科学领域的透射电子显微镜（TEM）基础知识。通过学习，您将理解相关文献中如何应用TEM，并具备进行TEM实践培训的必要理论基础。现代TEM作为单用户操作的仪器，提供了无与伦比的分析平台，能够获取从微米到亚埃级别的结构和化学信息。在薄的电子透明样本中，可以测量晶体结构、晶粒大小、缺陷以及化学成分。晶格可以以原子分辨率成像，从而观察晶界和界面，是研究纳米颗粒的唯一直接结构分析方法。 通过本课程，您将深入了解现代TEM与以下内容之间的联系： - 仪器的光学原理和操作方法； - 电子-物质相互作用的物理学； - 样品的材料特性。 这为您提供了背景，以： - 确定适合特定科学问题的TEM技术； - 解读文献中呈现的TEM数据，欣赏技术进步的影响，例如通过像差校正实现亚埃级分辨率。 课程还可以为后续在该卓越仪器上进行实践培训奠定基础，并为学习诸如“暗场全息术”或“角分辨电子能量损失光谱”等高级技术铺平道路。 推荐背景： 学习者需具备晶体学和衍射的基础知识，大学光学（光线图的构建）是必备前提；傅里叶光学、更高级的晶体学和固态物理将具有很大优势。 课程大纲： 1. 介绍：本周将介绍仪器，包括一些历史背景以及透射电子显微镜的基本构成部分。其次，我们将回顾TEM相关的主要像差。 2. 介绍（II）：我们将学习如何从单个组件（透镜和光阑）构建显微镜，并回顾显微镜的操作模式。 3. 衍射基础（I）：我们讨论TEM中在布拉格角下的2束衍射，并展示如何用Ewald球/倒易晶格表述。 4. 衍射基础（II）：介绍多束衍射和动力光散射的基础理论，探讨TEM样品大小和形状如何影响衍射点强度。 5. 衍射与成像：动力效应（I）：本周我们将研究TEM中的动力散射，并用理论表达式计算不同样品条件下的束流强度图。 6. 衍射与成像：动力效应（II）：探讨动力散射如何在TEM图像和衍射图样形成中产生影响。 7. 相位对比（I）：定义物镜的对比传递函数，并讨论对电子波相位的微弱影响。 8. 相位对比（II）：详细分析相位对比传递函数，理解薄无定形膜图像中的对比，并探讨晶体样品的高分辨率图像。 通过此课程的学习，您将对透射电子显微镜的原理和应用有更深入的理解，为未来的研究和实践打下坚实的基础。
Name:Introduction
Description:This week will be devoted to an introduction to the instrument, with some historical notes, as well as a review of the building blocks of a transmission electron microscope. In a second part, we will review the main lens aberrations relevant in transmission electron microscopy.
Name:Introduction (II)
Description:This week, we will see how to build the microscope from its individual components: lenses and aperture. Then we will have a review of the operating modes of the microscope.
Name:Diffraction basics (I): Ewald sphere / Reciprocal lattice
Description:In this week on the basics of electron diffraction we discuss the case of 2-beam diffraction at the Bragg angle in TEM and then show how it can be represented by the Ewald sphere/reciprocal lattice construction.
Name:Diffraction basics (II): Multi-beam / Kinematical scattering
Description:In this week we finish on the basics of electron diffraction, by first taking a look at zone axis or multi-beam diffraction where we have scattering from many different crystal planes at the same time. Next, we explain this by a relaxation of the Bragg condition in the Ewald sphere/reciprocal lattice construction resulting from the TEM sample size and shape. We then see how this affects diffraction spot intensity when slightly deviated from the perfect Bragg condition in the 2-beam case.
Name:Diffraction and imaging: Dynamical effects (I)
Description:In this week we will tackle the subject of dynamical scattering in TEM. Dynamical scattering is multiple elastic scattering; it effectively involves the diffraction and rediffraction of electrons as they transmit through a sample. In the first lecture, we look at the basic theory of dynamical scattering in the 2-beam case and use the theoretical expressions to calculate plots of beam intensity versus excitation error for different specimen conditions. In the next lecture, we use this theory to explain the dynamical scattering phenomenon of thickness fringes.
Name:Diffraction and imaging: Dynamical effects (II)
Description:This week we look at more effects of dynamical scattering, on both TEM images and diffraction pattern formation. First we look at how dynamical scattering produces bend contours in bright-field and dark-field images when the crystal lattice is bent across an imaged region of TEM sample. Secondly, a special case of dynamical scattering called double diffraction is introduced, in which multiple elastic scattering leads to the formation of diffraction spots for crystal planes which are systematic absences.
Name:Phase contrast (I)
Description:In this first week about phase contrast, we will define the contrast transfer function of the objective lens. In a second part we will consider an object that affects only weakly the phase of the electron wave and not its amplitude. This will lead us to the definition of the phase contrast transfer function.
Name:Phase contrast (II)
Description:In this week we will analyse more in details the Phase Contrast Transfer Function, and see how it can be used to understand the contrast in the image of a thin amorphous film. In a second part, we will address the high resolution images of crystalline specimens.
Learn about the fundamentals of transmission electron microscopy in materials sciences: you will be able to understand papers where TEM has been used and have the necessary theoretical basis for taking a practical training on the TEM. This course provides a comprehensive introduction to transmission electron microscopy (TEM) in the field of materials science. For an instrument operated by a single user, modern TEM provides an analytical platform with unsurpassed versatility, giving access to structural and chemical information from the micrometer to the sub-angstrom scale. In a thin, electron-transparent sample one can measure the crystallinity, grain structure, size, and defects, and the chemical composition. The crystal lattice can be imaged with atomic resolution, allowing observation of grain boundaries and interfaces. It is the only direct structural analysis method for studying nanoparticles. With this course you will gain a deep understanding of modern TEM and the connection between: - the optics and operation of the instrument; - the physics of electron-matter interactions; - insights into the materials properties of the sample. This gives the background to: - identify TEM techniques suitable to solving specific scientific problems; - interpret TEM data presented in articles; appreciate the impact of technological advances that have, for instance, led to sub-angstrom resolution by aberration correction. It can also be the basis for subsequent practical training on this remarkable instrument, and a stepping stone towards learning very advanced techniques with magical names like “dark field holography” or “angular resolved electron energy-loss spectroscopy”. Recommended background: Basics of crystallography and diffraction, college optics (construction of ray diagrams) are absolutely mandatory prerequisites; Fourier optics, more advanced crystallography and solid state physics are of great advantage.
