Principles of Scanning Electron Microscopy

This lecture discusses the principles of scanning electron microscopy at high specimen chamber pressures, focusing on wet specimen techniques, differential pressure limiting apertures, and vacuum system modifications. It covers the mechanics of protecting the electron beam from high pressure, the design of pressure limiting apertures, and the characteristics of the vacuum system. The lecture also explores the effects of different final aperture diameters on chamber pressure, the conductance of the system, and the implications for electron optics columns. Additionally, it examines the microstructures of magnesium hydride catalyzed with Ni nano-particles or Nb2O5, detailing the micrographs, X-ray diffraction, and X-ray absorption spectroscopy measurements.

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PHYS-405: Experimental methods in physics

The course's objectivs are: Learning several advenced methods in experimental physics, and critical reading of experimental papers.

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.

Cryogenic electron microscopy

Cryogenic electron microscopy (cryo-EM) is a cryomicroscopy technique applied on samples cooled to cryogenic temperatures. For biological specimens, the structure is preserved by embedding in an environment of vitreous ice. An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane. While development of the technique began in the 1970s, recent advances in detector technology and software algorithms have allowed for the determination of biomolecular structures at near-atomic resolution.

Electron diffraction

Electron diffraction refers to changes in the direction of electron beams due to interactions with atoms. Close to the atoms the changes are described as Fresnel diffraction; far away they are called Fraunhofer diffraction. The resulting map of the directions of the electrons far from the sample (Fraunhofer diffraction) is called a diffraction pattern, see for instance Figure 1. These patterns are similar to x-ray and neutron diffraction patterns, and are used to study the atomic structure of gases, liquids, surfaces and bulk solids.

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.

Advanced TEM Operation

Covers advanced operation techniques for a Transmission Electron Microscope (TEM), including setting up the workset and fine-tuning the image.

STEM: Scanning Transmission Electron Microscopy MSE-352: Introduction to microscopy + Laboratory work

Explores Scanning Transmission Electron Microscopy (STEM) principles, detectors, contrast mechanisms, and applications in high-resolution imaging.

Microscopy in situ and TEM Q&A MSE-352: Introduction to microscopy + Laboratory work

Explores in situ electron microscopy applications, traction experiments, environmental effects, XRD, and EDS.

Electron Microscopy Components MSE-352: Introduction to microscopy + Laboratory work

Covers electron microscope components, vacuum systems, aberrations, detectors, and specimen holders.

Dose Management in Electron Microscopy

Explores the challenges and solutions for managing electron dose in microscopy, emphasizing the importance of accurate dose tracking and analysis.