Lecture

Scanning Electron Microscopy: Basics

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In course

CH-410: Physical and chemical analyses of materials

The course relates on the use of electromagnetic (X-Ray) and corpuscular (electrons) radiations for physical and chemical analysis of solid materials. ...

Description

This lecture introduces the basics of Scanning Electron Microscopy (SEM), starting with its principle demonstrated in 1938. SEM is dedicated to massive samples, providing surface and topographical analyses. It involves electron-sample interactions, detectors, sample preparation, and image formation. The lecture covers topics such as electron sources, objective lens, working distance, scanning coils, detectors, sample relaxation, and contrasts in SEM images. It also discusses resolution, magnification, depth of field, and various contrasts observed in SEM, including topographic, chemical, and crystalline contrasts. Additionally, it explores other contrasts like surface crystalline, magnetic, and electrical potential contrasts, as well as different imaging techniques like absorbed electron imaging, transmitted electron imaging, cathodoluminescence imaging, and XRMA and AES imaging.

Instructor

Christophe Roussel

Habilitation à Diriger les Recherches (HDR) in chemistry at the Ecole Normale Supérieure Paris-Saclay (Cachan, France)PhD Thesis in physical organic chemistry at the University of Bourgogne Franche-Comté (Besançon, France) / Ecole Normale Supérieure Paris-Saclay (Cachan, France)

Official source

Related concepts (32)

Scanning electron microscope

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the intensity of the detected signal to produce an image.

Transmission electron microscopy

Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device.

Electron microscope

An electron microscope is a microscope that uses a beam of electrons as a source of illumination. They use electron optics that are analogous to the glass lenses of an optical light microscope. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light, electron microscopes have a higher resolution of about 0.1 nm, which compares to about 200 nm for light microscopes.

Scanning transmission electron microscopy

A scanning transmission electron microscope (STEM) is a type of transmission electron microscope (TEM). Pronunciation is [stɛm] or [ɛsti:i:ɛm]. As with a conventional transmission electron microscope (CTEM), images are formed by electrons passing through a sufficiently thin specimen. However, unlike CTEM, in STEM the electron beam is focused to a fine spot (with the typical spot size 0.05 – 0.2 nm) which is then scanned over the sample in a raster illumination system constructed so that the sample is illuminated at each point with the beam parallel to the optical axis.

Contrast agent

A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiopharmaceuticals, which emit radiation themselves. In x-ray imaging, contrast agents enhance the radiodensity in a target tissue or structure. In magnetic resonance imaging, contrast agents shorten (or in some instances increase) the relaxation times of nuclei within body tissues in order to alter the contrast in the image.

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