1.1 - Introduction to transmission electron microscopy (TEM)

Summary

In this introductory course on Transmission Electron Microscopy (TEM), Professor Calvin Shear from Texas A&M University offers a comprehensive overview of TEM's principles and applications. He shares his academic background and research experience using TEM in various studies, including materials characterization and phase transformations. The course covers five sections: basics, diffraction, imaging, spectroscopy, and related TEM techniques. It utilizes several key textbooks and resources, emphasizing the structural and chemical information TEM provides. The course also highlights advanced TEM techniques like aberration correction and scanning transmission electron microscopy (STEM).

Takeaways

• 🤠 The course is an introduction to Transmission Electron Microscopy (TEM), taught by Calvin Shear, an assistant professor in the Department of Material Science and Engineering at Texas A&M University.
• 🎓 Calvin Shear has a diverse academic background, with undergraduate studies in biomedical engineering and finance at the University of Sydney, and a PhD in mechanical engineering focusing on high-strength low-alloy steel.
• 🔬 TEM and Atom Probe were key tools in his research during his PhD to study solute clusters, and post-PhD, he worked at Johns Hopkins University, using TEM to study deformation mechanisms in boron carbide and magnesium.
• 🧑‍🏫 The course will cover a wide range of topics, including electron scattering, instrumentation, sample preparation, diffraction, imaging, spectroscopy, and related TEM techniques.
• 📚 The main textbook for the course is 'Transmission Electron Microscopy' by Williams and Carter, supported by other resources like 'Microstructural Characterization of Materials' and 'Aberration-Corrected Imaging'.
• 🖼️ Five main sections of the course include basics, diffraction, imaging, spectroscopy, and TEM-related techniques, with detailed discussions on each topic.
• 💡 In the basics, the course will explore electron scattering, electron sources, and lenses, as well as sample preparation methods like electro-polishing and lift-out for specific samples.
• 📐 The diffraction section covers parallel beam diffraction, Kikuchi diffraction, and convergent beam electron diffraction, explaining how each provides different visual patterns (spots, lines, disks).
• 🔍 Imaging will delve into three types of contrast (mass-thickness, diffraction, and phase contrast) to analyze different materials and samples at atomic resolution.
• 🌈 The spectroscopy section introduces EDS and EELS techniques, enabling students to gather both chemical and bonding information about materials, particularly when combined with scanning TEM and aberration correction.

Q & A

What is the main focus of this Transmission Electron Microscopy (TEM) class?

The main focus of this class is to provide an overview of Transmission Electron Microscopy (TEM) and its applications in material science.

Who is the instructor of the class, and what is his academic background?

The instructor is Calvin Shear, an assistant professor in the Department of Material Science and Engineering at Texas A&M University. He has a background in biomedical engineering and finance from the University of Sydney and a PhD in mechanical engineering.

What technique is emphasized in this course that is specific to Texas A&M University?

The course emphasizes the use of a special TEM technique called precession electron diffraction, which is used to study the formation and phase transformations in materials.

Which textbook is primarily used for this course, and what is its significance?

The textbook used is 'Transmission Electron Microscopy' by Williams and Carter, often referred to as the 'Bible' for TEM due to its comprehensive coverage of the subject.

What are the five main sections of the TEM course as outlined by the instructor?

The five main sections of the course are basics, diffraction, imaging, spectroscopy, and TEM-related techniques.

What are the three types of contrast discussed in the imaging section of the course?

The three types of contrast discussed are mass-thickness contrast, diffraction contrast, and phase contrast. These contrasts help in imaging biological samples, crystal defects, and atomic structures, respectively.

What are the two spectroscopy techniques covered in the course, and what information do they provide?

The two spectroscopy techniques are Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS). EDS provides chemical information, while EELS offers both chemical and chemical bonding information.

How does the instructor describe the impact of aberration correction in TEM imaging?

The instructor explains that aberration correction in TEM significantly improves image quality. He shows an example where an aberration-corrected image reveals more detailed atomic structures compared to a non-corrected image.

What is the significance of combining EDS and EELS with STEM in the context of this course?

Combining EDS and EELS with Scanning Transmission Electron Microscopy (STEM) allows for the chemical analysis of individual atomic columns, providing highly detailed structural and chemical information.

What is the expected outcome for students by the end of this TEM course?

By the end of the course, students are expected to have a good understanding of how TEM works and how it can be applied to research in material science.

Outlines

00:00

👋 Introduction to Transmission Electron Microscopy (TEM)

In this introductory section, Professor Calvin Shear welcomes the audience to his course on Transmission Electron Microscopy (TEM). He provides an overview of his background, including his undergraduate studies in biomedical engineering and finance at the University of Sydney, followed by a PhD in mechanical engineering. His research involved using TEM and atom probe techniques to study high-strength alloy steels. Afterward, he joined Johns Hopkins University to investigate deformation mechanisms in materials like boron carbide and magnesium, eventually becoming a microscopy faculty member at Texas A&M University, specializing in advanced TEM techniques.

05:01

📚 Course Materials and Structure

This section outlines the primary textbook for the course, *Transmission Electron Microscopy* by Williams and Carter, which is considered essential for TEM studies. Additional resources include *Microstructural Characterization of Materials* by Brendan and Kaplan and *Introduction to Scanning Electron Microscopy*. The course will cover five major sections, each corresponding to a YouTube playlist: basics, diffraction, imaging, spectroscopy, and advanced TEM techniques. Each section will dive deep into the various methods and topics in TEM, preparing students for advanced research in material science.

🔬 Basics of Electron Scattering and Instrumentation

In the basics section of the course, Professor Shear will discuss electron scattering and the fundamental components of a TEM instrument, including electron sources, lenses, and the importance of sample preparation. The two examples of sample preparation methods include electro-polishing for metal samples and site-specific lift-out techniques. This foundational knowledge sets the stage for further exploration of how TEM works and how samples are prepared for analysis.

📐 Electron Diffraction Techniques

This paragraph introduces electron diffraction, explaining how and why diffraction occurs within a TEM. Various diffraction techniques are explored, such as parallel beam diffraction, Kikuchi diffraction, and convergent beam electron diffraction (CBED). Each method produces different visual outcomes—spots, lines, or disks—that help researchers analyze material structures. These diffraction techniques are essential for understanding crystallographic information.

🌈 Imaging and Contrast in TEM

In this part of the course, different types of imaging and contrast mechanisms in TEM are discussed. Professor Shear explains three types of contrast—mass thickness contrast, diffraction contrast, and phase contrast—each used to visualize different material features, such as biological samples or crystallographic defects. Examples include high-resolution TEM images showing atomic-level details like nano twins in boron carbide, with applications in understanding material deformation and structure.

📊 Spectroscopy Techniques in TEM

This section covers spectroscopy techniques that provide chemical information about materials. Two key methods—Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS)—are introduced. EDS helps in identifying chemical compositions, while EELS offers insights into chemical bonding. Examples include comparing EELS spectra for diamond, carbon 60, and graphite, showing how these techniques can reveal subtle material differences at the atomic level.

🧪 Advanced TEM Techniques and Applications

The final section delves into advanced TEM techniques, including Scanning Transmission Electron Microscopy (STEM) and precession electron diffraction, which can be compared to Electron Backscatter Diffraction (EBSD). Aberration-corrected TEM is highlighted as a powerful tool for achieving high-resolution images, with examples showing the dramatic improvements in image clarity when aberration is corrected. The course aims to equip students with the skills to understand and apply these advanced techniques in their research.

Keywords

💡Transmission Electron Microscopy (TEM)

Transmission Electron Microscopy (TEM) is a technique that uses a beam of electrons to pass through a sample to create high-resolution images. It allows for detailed structural analysis of materials at the atomic level. In the video, TEM is the central focus, and the course aims to teach its applications, from imaging to diffraction.

💡Electron Diffraction

Electron diffraction refers to the phenomenon where electrons are scattered by the atomic lattice of a material, producing diffraction patterns. These patterns provide information about the material's crystal structure. The video mentions several types of electron diffraction (parallel beam, Kikuchi, converging beam), which are key to analyzing materials in TEM.

💡Sample Preparation

Sample preparation involves techniques to prepare materials for TEM analysis, ensuring that they are thin enough for electrons to pass through. In the video, methods such as electro-polishing and lift-out are highlighted as essential for studying specific material types like metals and site-specific samples.

💡Mass Thickness Contrast

Mass thickness contrast is a type of contrast in TEM imaging that arises from differences in the thickness and atomic mass of the material. Heavier or thicker areas appear darker. The video uses the example of biological samples, like mitochondria, to explain how this contrast helps visualize different material structures.

💡Diffraction Contrast

Diffraction contrast is used in TEM to image crystal defects such as dislocations and stacking faults. It is created when electrons are scattered by different parts of the crystal, leading to contrast. In the video, the instructor shares examples from his own research, showing dislocations in high-strength alloys.

💡Spectroscopy

Spectroscopy in TEM refers to techniques that provide chemical information about the sample, complementing structural data. The video discusses two main types: Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS). These methods are used to identify chemical composition and even chemical bonding at the atomic level.

💡Aberration Correction

Aberration correction is a technique in TEM that improves image resolution by correcting optical distortions caused by lenses. The video contrasts images with and without aberration correction, showing how this technique allows for clearer atomic-level visualization. This is crucial for studying fine structural details.

💡Precession Electron Diffraction

Precession Electron Diffraction is a specialized TEM technique that enhances diffraction data by reducing dynamical effects. It can be seen as analogous to EBSD (Electron Backscatter Diffraction) but inside a TEM. The video explains its importance in material phase transformations and crystallographic studies.

💡High-Resolution TEM (HRTEM)

High-Resolution TEM (HRTEM) allows for atomic-scale imaging, providing detailed information about the arrangement of atoms in a material. The video refers to HRTEM while explaining phase contrast, which enables the visualization of atomic-level defects like nano twins in materials such as boron carbide.

💡Energy Dispersive X-ray Spectroscopy (EDS)

Energy Dispersive X-ray Spectroscopy (EDS) is a TEM-based technique used to determine the elemental composition of materials by detecting X-rays emitted from the sample during electron beam interaction. The video emphasizes its role in combining structural and chemical information, particularly in high-precision material analysis.

Highlights

Introduction to Transmission Electron Microscopy (TEM) by Calvin Shear, Assistant Professor at Texas A&M University.

Calvin Shear's academic background includes a Bachelor’s degree in Biomedical Engineering and Finance from the University of Sydney, and a PhD in Mechanical Engineering.

Shear’s PhD research utilized both TEM and Atom Probe to study solar clusters in high-strength, low-alloy steel.

After his PhD, Shear joined Johns Hopkins University, where he used TEM to study deformation mechanisms in boron carbide and magnesium.

In 2018, Shear became part of Texas A&M University’s Department of Material Science and Engineering, focusing on microscopy.

At Texas A&M, Shear uses a specialized TEM technique called Precession Electron Diffraction to study material formation and phase transformation.

The course’s primary textbook is 'Transmission Electron Microscopy' by Williams and Carter, commonly referred to as the 'Bible' for TEM.

Additional resources include 'Microstructural Characterization of Materials' by Brandon and Kaplan, and 'Aberration-Corrected Imaging in Transmission Electron Microscopy' by Erni.

The TEM course is divided into five sections: basics, diffraction, imaging, spectroscopy, and TEM-related techniques.

The basics section covers electron scattering, electron sources, lenses, and sample preparation techniques like electro-polishing and lift-out methods.

Electron diffraction is explained with various techniques, including Parallel Beam Diffraction (spots), Kikuchi Diffraction (lines), and Converging Beam Electron Diffraction (disks).

The course emphasizes three types of contrast in TEM imaging: mass-thickness contrast, diffraction contrast, and phase contrast.

Spectroscopy section focuses on Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS), providing chemical and bonding information.

Advanced TEM techniques include Scanning Transmission Electron Microscopy (STEM), Precession Electron Diffraction, and Aberration-Corrected TEM.

By the end of the course, students are expected to understand how TEM works and how it can enhance their research.

Transcripts

howdy welcome to my introduction to the

transmission electron microscopy class

my name is Calvin shear and I am an

assistant professor in the Department of

material science and engineering at

Texas A&M University

the aim of this online class is to give

you an overview of what is TEM and what

he young can do or just use one slide to

share with you my background I did my

undergraduate studies at University of

Sydney in Australia my bachelor degrees

from biomedical engineering believe it

or not I also have a degree in finance

aizen State at the University of Sydney

and completed my PhD in the Department

of Mechanical Engineering my PhD

advisors are professors Judy carne and

the Simon ringer during my PhD are used

both TEM and Adam probe to study the

solar clusters in a high strength low

alloy steel after my PhD a joint

professor Kevin Henkes group at Johns

Hopkins University

I was the in-house TEM person and using

TEM as at all to study the defamation

mechanisms in boron carbide and a

magnesium in 2018 I joined the

department of material science and

engineering at Texas A&M as a microscopy

faculty at Texas A&M we use a special TM

technique called precession electron

diffraction to study the formation and

the phase transformation in materials

the textbook were going to use for this

course is transmission electron

microscopy by Williams and Carter this

is also referred as the Bible for TEM to

complement the Williams and Carter books

we will also use the resources from a

few other books the first one is the

micro structural characterization of

materials by Brendan and Kaplan a few

chapters of the book are devoted to TM

and a TM based techniques if you want to

have a quick read about TM it's a very

nice book we will also use the

information from introduction to

scanning electron microscopy or stem the

last one is the aberration corrected

imaging inference electron microscopy by

Ernie there will be five sections of

this TM course all five playlists on

YouTube

there will be on the basics diffraction

imaging spectroscopy and other TM

related techniques in basics we'll start

by talking about the electron scattering

in TEM the were moved to the

instrumentation talking about the

electron sources lenses etc we will also

talk about sample preparation in these

two examples specifically the one on the

left is electro polishing to prepare

metal samples the one on the right is a

lift out for site-specific samples the

second section is on electron

diffraction both talked about why and

how diffraction happens in TEM we will

then discuss the parallel beam

diffraction and indexing Kikuchi

diffraction and convergence beam

diffraction in parallel beam diffraction

you see spots in Kikuchi diffraction you

see lines in converging beam electron

diffraction you see disks in the third

section of this course or discuss

imaging and is the origin of contrast

there are three types of contrast mass

thickness contrast diffraction contrast

and face contrast the mass thickness

contrast is used to image stained

biological samples the example here

shows the mitochondria in a Cell

diffraction contrast is used to image

crystal graphic defects such as

dislocations and stacking faults the

examples showing here are from my own

research with Professor Kevin honker the

dark lines in the left figure and the

bright lines in the right figure artists

locations the reason we can see the

atomic level information in high-res DM

images is due to the face contrast again

this example was from my own research

with Professor Kevin honker showing the

nano twins in a boring car by sample the

fourth section is spectroscopy imaging

and the diffraction will give you the

structural information spectroscopy will

give you the chemical information the

two spectroscopy techniques going to

discuss our energy dispersive x-ray

spectroscopy EDS and electron energy

loss spectroscopy eels using EDS you can

get the chemical information using eels

in addition to the chemical information

you can also get the chemical bonding

information from this example here you

can see the eros spectrum of diamond

looks very different from carbon 60 and

graphite combining EDS and eels with

stem using an aberration corrected TEM

you can get the chemical information of

individual atomic columns the figure

here is from Cornell University and it's

just striking

in the last section we'll introduce some

tea and related techniques the first one

is the scanning transmission electron

microscopy stem these stem images were

acquired by my student Hershey

highlighting the nano precipitates in a

shape memory alloy we will also talk

about the precession electron

diffraction this technique can be

somewhat viewed as EB SD inside TEM

lastly we'll talk about is the

aberration corrected TEM the micrographs

were taken from the Williams and Carter

book the image on the left has no

aberration correction while the one on

the right is with the aberration

correction you can see the difference

straight away at the end of this course

I hope you will be able to develop a

good understanding on how TM works and

what TM can do to help your research in

the next video we'll talk about why we

use electron inside TEM and the

resolution of TEM