Transmission electron microscopy for materials science

Go to Course: https://www.coursera.org/learn/microscopy

Introduction

# Course Review: Transmission Electron Microscopy for Materials Science on Coursera ### Overview The "Transmission Electron Microscopy for Materials Science" course on Coursera offers a comprehensive introduction to the fundamentals of transmission electron microscopy (TEM) tailored specifically for materials science applications. For those looking to deepen their understanding of this powerful analytical tool, the course provides not only theoretical knowledge but also insights into practical applications. With TEM being an irreplaceable asset in materials characterization, this course is ideal for researchers, students, and professionals who wish to navigate and interpret scientific literature and effectively utilize TEM in their work. ### Course Structure The course is well-structured, unfolding over a series of thoughtfully designed modules: 1. **Introduction**: The course kicks off with an overview of the transmission electron microscope, exploring its history and the key components that constitute the instrument. Participants will learn about significant lens aberrations and their implications in imaging. 2. **Building the Microscope**: This module dives deeper into the construction of a TEM, examining individual components such as lenses and apertures, as well as various operating modes of the microscope, which is crucial for understanding the mechanics behind TEM imaging. 3. **Diffraction Basics (I & II)**: These segments introduce participants to the essentials of electron diffraction. Topics such as the Ewald sphere, reciprocal lattice, and multi-beam diffraction are discussed, providing a solid basis for understanding how diffraction impacts imaging. 4. **Dynamical Effects in Diffraction and Imaging (I & II)**: A more advanced exploration of dynamical scattering is presented, encompassing the mathematical treatment of thickness fringes and the effects of bent crystal lattices on imaging. This section is vital for grasping the complexities inherent in TEM data. 5. **Phase Contrast (I & II)**: This part defines the contrast transfer function and delves into phase contrast in images, including how to analyze high-resolution images of crystalline materials and the unique behaviors of thin amorphous films. ### Learning Outcomes Students who successfully complete the course will confidently grasp the theoretical underpinnings of TEM, enabling them to: - Understand and analyze scholarly articles utilizing TEM. - Apply knowledge of lens aberrations and diffraction to their own research. - Interpret diffraction patterns and imaging results through the lens of dynamical scattering and phase contrast. ### Who Should Enroll? This course is particularly beneficial for: - Graduate students in materials science or related fields. - Researchers looking to enhance their microscopy skills. - Industry professionals involved in materials characterization. ### Recommendation I highly recommend the "Transmission Electron Microscopy for Materials Science" course for anyone seeking to develop a robust understanding of TEM principles and their application in materials analysis. The combination of theoretical instruction with practical implications allows for a complete learning experience. With the invaluable skill set gained from this course, participants will be equipped to engage with advanced materials research and apply TEM techniques to their scientific inquiries. Whether you are starting your journey in materials science or looking to expand your technical toolkit, this course is a step in the right direction. ### Conclusion Overall, Coursera’s offering of "Transmission Electron Microscopy for Materials Science" stands out as a must-take course for current and aspiring professionals in the field. The course content is rich and caters to a broad audience, making it a valuable resource for anyone interested in the intricacies of materials characterization through transmission electron microscopy.

Syllabus

Introduction

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.

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.

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.

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.

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.

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.

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.

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.