Electron microscopes are at the forefront of key innovations in science, engineering and medicine. Materials scientists, physicists, chemists, biochemists and engineers use electron microscopy to address fundamental scientific problems and technological issues.
Electron microscopes are not new. Ernst Ruska and Max Knoll, from the University of Berlin, developed the first transmission electron microscope (TEM) in 1931. In 1937, Manfred von Ardenne from the Electron Physics Research Laboratory in Helsinki developed the first scanning electron microscope (SEM).
Both SEM and TEM instruments are extensively used today in science, engineering and medicine research. As the name suggests, electron microscopes use electrons for imaging as compared with light, which is used by standard optical microscopy.
As electrons have smaller wavelengths than visible light, electron microscopes surpass the limitations of optical microscopes and make it possible to view microscopic objects down to atomic scale. In addition SEMs are typically equipped with ion columns that enable volume scoping of materials, facilitating three-dimensional imaging of morphology, structure and composition using secondary electrons, backscattered diffracted electrons and fluorescent X-rays.
Dalaver H. Anjum
is an assistant professor of physics at Khalifa University.
Similarly, TEMs let us explore material chemistry at atomic resolutions. Consequently, electron microscopes routinely let us view objects at the billionth of a meter (nanometer) resolution or better to characterize structure and chemical and physical properties or materials.
Electron microscopes support the imaging of materials spanning applications from engineering to health care. Analyses include two-dimensional (2D) materials, battery technology, oil and gas exploration, interplanetary dust particles and viruses, including the infamous COVID-19 virus.
Modern TEMs also image magnetic fields in materials at nanometer scales. The layered magnetic materials have applications for spintronics and quantum computing, to gain insights into intrinsic spin of the electrons and associated magnetic moments.
Research efforts in 2D materials critically depend upon the data generated with electron microscopes. Electron microscopes help to characterize the structure and properties of 2D materials at atomic-scale resolutions.
Materials properties that can be investigated with electron microscopes include optical, electronic, ferroelectric and ferromagnetic. Moreover, electron microscopes are crucial for obtaining information on the integration of different types of 2D materials with each other or bulk materials. Additionally the imaging of surface plasmons in metal structures near infrared frequencies help to develop materials with applications for future generations of wireless communications, including 6G and beyond.
The focused-ion beam-equipped SEMs in combination with TEMs also offer excellent materials-characterization opportunities for the macro-to-micro scale analysis of metals, semiconductors and soft matter such as polymer membranes and biomaterials. In each case, materials’ morphology, crystal structure and elemental composition can be studied in two or three dimensions with unparalleled spatial and energy resolutions.
Using electron microscopy to examine materials at cryogenic temperatures is called cryo-EM, and it lets us analyze biological and soft materials in their frozen but native states. These materials include bacteria, cells and viruses.
Cryo-EM has also become one of most widely used technologies and is integral to today’s drug-discovery efforts. Moreover, cryo-electron tomography (cryo-ET) of frozen but electron transparent thin cellular sections allows researchers to visualize the proteins at nanometer resolutions inside cells. The COVID-19 vaccine’s development demonstrated the method’s importance; its role is expected to become even more critical in pharmaceutical applications.
Electron microscopes are indispensable tools for supporting discoveries in experimental science, engineering and medicine. And using electron microscopes can support enabling future next-generation wireless technologies, artificially intelligent devices, light-metal alloys, energy-related materials and vaccine developments.
