Foundations in Electron Microscopy (EM) and Its Related Spectroscopies
A.Y. 2024/2025
Learning objectives
The course is a general introduction to both physical principles and applications of the only technique capable of providing both imaging and compositional characterization with the best resolution currently available: electron microscopy (EM). Electron microscopy is based on common physical principles, which will be illustrated in the course, but can be performed in diverse operational modes: scanning (SEM), transmission (TEM), high resolution transmission (HRTEM) and scanning transmission (STEM). The physical principles, as well as aims, advantages and limits of each EM operational mode will be presented. Furthermore, since electron microscopy is based on the interaction between an electron beam and an object whose shape, size, possible crystalline structure and composition, the latter also spatially resolved, have to be investigated, the spectroscopies exploiting the signals originated by that interaction will be introduced. It will be then explained how they are capable to also provide the researchers with qualitative and quantitative information about chemical composition of the imaged samples: it's the so-called Analytical EM (AEM).
Thus, the main goal of the course is to provide its attendees with a broad overview of the modes in which electron microscopy is carried out, concomitantly underlining why it has been subjected of a never-ending development and improvement, being EM able to reveal insights on morphological, structural and compositional details of the investigated samples with spatial resolution that no other analysis technique is capable to reach.
Thus, the main goal of the course is to provide its attendees with a broad overview of the modes in which electron microscopy is carried out, concomitantly underlining why it has been subjected of a never-ending development and improvement, being EM able to reveal insights on morphological, structural and compositional details of the investigated samples with spatial resolution that no other analysis technique is capable to reach.
Expected learning outcomes
At the end of the course, a student who attended it is expected:
1. to know the origin, development and physical principles on which electron microscopy is based;
2. to understand the aims and effectiveness of the different operational modes in electron microscopy, as well as the related limitations and how these can be addressed;
3. to get the chance, through experimental sessions, to observe both structure and way to operate a SEM and a TEM, and to observe by the diverse EM instruments some samples prepared for this purpose. Furthermore, the main aim of the practical sessions is to show why it's needed knowing the physics behind EM instruments in order to bring them into optimal working conditions (alignment procedures).
Finally, a short seminar (see below) is expected as a mandatory part of the final exam made by each student. In such a seminar, the student will have to both show and discuss a topic strongly related with the course content, and its possible applications. As well, the seminar aims to train a student to both briefly illustrate a topic of his/her choice clearly, rigorously and concisely, and to answer some questions that could be raised on it.
1. to know the origin, development and physical principles on which electron microscopy is based;
2. to understand the aims and effectiveness of the different operational modes in electron microscopy, as well as the related limitations and how these can be addressed;
3. to get the chance, through experimental sessions, to observe both structure and way to operate a SEM and a TEM, and to observe by the diverse EM instruments some samples prepared for this purpose. Furthermore, the main aim of the practical sessions is to show why it's needed knowing the physics behind EM instruments in order to bring them into optimal working conditions (alignment procedures).
Finally, a short seminar (see below) is expected as a mandatory part of the final exam made by each student. In such a seminar, the student will have to both show and discuss a topic strongly related with the course content, and its possible applications. As well, the seminar aims to train a student to both briefly illustrate a topic of his/her choice clearly, rigorously and concisely, and to answer some questions that could be raised on it.
Lesson period: Second semester
Assessment methods: Esame
Assessment result: voto verbalizzato in trentesimi
Single course
This course can be attended as a single course.
Course syllabus and organization
Single session
Responsible
Lesson period
Second semester
Course syllabus
General introduction to Electron Microscopy: historical notes and short comparison with optical microscopy.
Electron microscopy, its diverse operational modes (SEM, TEM and STEM) and related instruments:
· Electron sources and physical principles on which they are based. Features: brightness, probe size, spatial and temporal coherence, stability, lifetime.
· Electron optics: magnetic lenses and associated aberrations, deflection coils, diaphragms. Depth of field.
Electron-specimen interactions and resultant imaging modalities:
o SEM: resolution and probe size, electron signals used, their origin and detectors. SEM imaging modes: high resolution, high depth of field, high current, low tension. Hints about the SEM samples preparation and VP-SEM (with some application).
Recap about crystallography and diffraction.
o TEM: diffraction contrast, amplitude contrast and phase contrast. TEM modes: bright and dark field. Hints about HRTEM, in situ TEM and TEM samples preparation.
· The electron microscopist's unavoidable nightmare: radiation damage, its consequences and how to limit it
Spectroscopical techniques associated with analytical electron microscopy (AEM):
· Energy Dispersive X-Ray Spectroscopy (EDS): principles and applications in SEM and TEM
· Electron Energy Loss Spectrometry (EELS): principles and applications. Low loss zone and high loss zone, ELNES and EXELFS.
· Compositional mapping: Spectrum Imaging and EFTEM
During the course several examples of SEM and TEM imaging applied to different kinds of materials will be shown and discussed.
At least 8 hours will be spent in practical (experimental) sessions on SEM and TEM, according to procedures to be defined depending on the number of students and the access conditions to the electron microscopes.
Electron microscopy, its diverse operational modes (SEM, TEM and STEM) and related instruments:
· Electron sources and physical principles on which they are based. Features: brightness, probe size, spatial and temporal coherence, stability, lifetime.
· Electron optics: magnetic lenses and associated aberrations, deflection coils, diaphragms. Depth of field.
Electron-specimen interactions and resultant imaging modalities:
o SEM: resolution and probe size, electron signals used, their origin and detectors. SEM imaging modes: high resolution, high depth of field, high current, low tension. Hints about the SEM samples preparation and VP-SEM (with some application).
Recap about crystallography and diffraction.
o TEM: diffraction contrast, amplitude contrast and phase contrast. TEM modes: bright and dark field. Hints about HRTEM, in situ TEM and TEM samples preparation.
· The electron microscopist's unavoidable nightmare: radiation damage, its consequences and how to limit it
Spectroscopical techniques associated with analytical electron microscopy (AEM):
· Energy Dispersive X-Ray Spectroscopy (EDS): principles and applications in SEM and TEM
· Electron Energy Loss Spectrometry (EELS): principles and applications. Low loss zone and high loss zone, ELNES and EXELFS.
· Compositional mapping: Spectrum Imaging and EFTEM
During the course several examples of SEM and TEM imaging applied to different kinds of materials will be shown and discussed.
At least 8 hours will be spent in practical (experimental) sessions on SEM and TEM, according to procedures to be defined depending on the number of students and the access conditions to the electron microscopes.
Prerequisites for admission
Knowledge of both classical physics, principles of modern physics, fundaments of crystallography (Bravais lattice, Miller indexes, Bragg's law, reciprocal space and lattice).
Teaching methods
Theoretical classes/lectures (38h) and practical (experimental) sessions on SEM and TEM (at least 6h), mainly on TEM and STEM. Attending the classes and the practical sessions is strongly recommended. The course is thought to be attended by students of the master's degree. Slides and any additional material will be made available in Ariel platform of the course dedicated website.
Teaching Resources
Classes slides/notes and further readings (i.e., scientific papers) downloadable from Ariel platform on the course dedicated website.
Texts/books for further reading:
Ray Egerton: "Physical principles of electron microscopy: an introduction to TEM, SEM, and AEM". Springer Ed.
David B. Williams, C. Barry Carter: "Transmission Electron Microscopy (a textbook for Materials Science)". Springer Ed.
Joseph I. Goldstein, Dale E. Newbury, Joseph R. Michael, Nicholas W.M. Ritchie, John Henry J. Scott, David C. Joy: "Scanning Electron Microscopy and X-Ray Microanalysis". Springer Ed.
Texts/books for further reading:
Ray Egerton: "Physical principles of electron microscopy: an introduction to TEM, SEM, and AEM". Springer Ed.
David B. Williams, C. Barry Carter: "Transmission Electron Microscopy (a textbook for Materials Science)". Springer Ed.
Joseph I. Goldstein, Dale E. Newbury, Joseph R. Michael, Nicholas W.M. Ritchie, John Henry J. Scott, David C. Joy: "Scanning Electron Microscopy and X-Ray Microanalysis". Springer Ed.
Assessment methods and Criteria
Oral exam on the whole program.
The purpose of the exam is checking both knowledge and understanding of the scientific fundaments of EM, i.e., the physics behind methods and phenomena described, and the experimental methodologies illustrated.
The final score is expressed out of thirty.
The purpose of the exam is checking both knowledge and understanding of the scientific fundaments of EM, i.e., the physics behind methods and phenomena described, and the experimental methodologies illustrated.
The final score is expressed out of thirty.
FIS/03 - PHYSICS OF MATTER - University credits: 6
Laboratories: 12 hours
Lessons: 35 hours
Lessons: 35 hours
Professor:
Falqui Andrea
Professor(s)