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Field emission scanning electron microscopy (FE-SEM) is a stable in the study of nanomaterials. Here, we discuss how this approach works, its role in nanoresearch, and the commercial suppliers of its instruments.  

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The FE-SEM enables high-resolution imaging at minimal accelerating voltages and working proximity. It has a magnification of 0.6 nanometer at 15 kV and 1.12 nanometer at 1 kV, which enables inspection of the upper surface of nanoparticles, nano-films, and nanofibers in a broad variety of applications including geology, ceramics, plastics, metals, electrical devices, biochemistry, chemistry, and biosciences.

Field emission is the only electronic source designed for high-resolution scanning and adaptable to a broad range of materials. It produces electrons through a field emitter gun (FEG). A scanning electron microscope (SEM) that uses FEG as the emission is known as a field emission scanning electron microscope (FE-SEM); the emission type is included in the name to distinguish it from a regular SEM.

FEG is made of tungsten wire with a width of about 100 nanometer, preferably a single crystal, with the crystal plane parallel to the electron visual axis. When the gun tip is near a +2-6 kV electrode, the precision of the point creates fields of 1000 V/m at its tip. This results in a substantially more focused stream of electrons traveling through the boundary into the vacuum.

Professor Crewe developed the first functional FE-SEM in 1968 at Argonne National Laboratory. FE-SEM was founded on the foundation of elevated imaging techniques and several processes aimed at characterizing the whole specimen.

FE-SEM is relevant to a wide variety of uses, including imaging of non-conductive and surface-sensitive materials without the need for pre-processing. Furthermore, FE-SEM has a range of appropriate analytical accessories. FE-SEM delivers topological and compositional data at magnifications ranging from 10x to 200,000x, with a nearly infinite focal length.

Compared to a conventional scanning electron microscope (SEM), field emission SEM generates pictures that are three to six times sharper, less electrostatically deformed, and have resolving power below one nanometer.

A beam of electrons is released from the scanning electron microscope by a tungsten filament. An electric potential of tens of eV to fifty keV accelerates this beam of electrons. These electrons are focused using rectifier lenses and an image sensor to produce a spot size of between one and five nanoneter. The beam rasters across the region to be scanned, with the sweep coils directing the beam. Several different imaging methods can be utilized depending on the pattern produced.

Field emission scanning electron microscopy provides unprecedented insight into the microstructures of nanomaterials such as thin films and nano-powders. Additionally, the signals generated by the sample can be utilized to determine the structure and composition of the nanomaterials.

FE-SEM is also used in nanotechnology for the study and examination of nanostructures and nanotubes, quantum dots, mesoporous structures, and nanocomposites.  All characterization techniques in nanotechnology largely depend on the usage of FE-SEMs, making  it one of the basic analysis techniques for the characterization of nanomaterials.

TESCAN is one of the leading brands which supplies FE-SEM equipment. The company's primary concentration is on the development, design, and manufacture of scientific tools and testing equipment, including optical microscopes, scanning electron microscopes (SEM), field emission scanning electron microscopes (FE-SEM), and microscope peripherals.

The firm is establishing a reputable name in the area of scanning electron microscopy design and manufacture, as well as system solutions for a variety of applications.

Shimadzu is another brand that supplies FE-SEM equipment throughout the world. This brand originated in India and has more than 140 years of experience in manufacturing world-class engineering equipment. Reliability-Proven Ultra-High-Resolution Field-Emission Scanning Electron Microscopes (FE-SEM) are also manufactured and supplied by the brand named Hitachi.

When it comes to innovative and state-of-the-art equipment, FE-SEM produced and supplied by JEOL has no competition. JEOL is committed to continuous innovation and is a proud supplier of the most sophisticated Field Emission Scanning Electron Microscope range.  The latest series of JEOL FE-SEMs has single-digit Angstrom accuracy at low kilo-voltage operation, as well as automated beam tuning and regulation.

The National Research Council awarded Illinois State University a $403,900 fund to acquire a scanning electron microscope that would help in education and research throughout campus and the surrounding region. The equipment, branded as a state-of-the-art field emission scanning electron microscope (FE-SEM), can capture photographs of a variety of nanoscale objects, allowing users to discover minute features and qualities. To put the minuscule size of nanoparticles into context, if a particle were the size of the planet, a nanoparticle would be the size of a single soccer ball on the globe.

The new instrument incorporates several unique characteristics. The addition of energy-dispersive X-ray spectrophotometry to the FE-SEM will aid in detecting the elements contained in the material and a nanometer-scale region of the substance. Cathodoluminescence may be used to determine the amount of light emitted by nanomaterials, which is important for determining the materials' optical characteristics. Researchers will be able to obtain an understanding of how these approaches are employed in science to visualize and analyze the structure of nanoscale objects.

A major benefit of FE-SEM is its capacity to evaluate contaminated zones with a reduced surface area using electron accelerating frequencies consistent with energy dispersive spectroscopy (EDS). It enables high-resolution, low-voltage photography with small sample electromagnetic charging. There is essentially no need to cover insulating materials with conductors.

On the other hand, one major disadvantage of FE-SEM as compared to conventional SEM is the cost of equipment. FE-SEM is considerably expensive as compared to conventional SEM and the maintenance cost of FE-SEM is also higher.

Alyamani, A. M., & Lemine, O. M. (2012). FE-SEM characterization of some nanomaterial. In Scanning electron microscopy. IntechOpen. Available at: htpps://doi.org/10.5772/34361

Brodusch, N. D. (2018). Field emission scanning electron microscopy: New perspectives for materials characterization. Springer. Available at: https://doi.org/10.1007/978-981-10-4433-5

Hatch, R. (2022). Illinois State awarded $403,900 NSF grant for state-of-the-art electron microscope. Illinois State University. [online]. Available at: https://news.illinoisstate.edu/2022/03/illinois-state-awarded-403900-nsf-grant-for-state-of-the-art-electron-microscope/

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Hussain graduated from Institute of Space Technology, Islamabad with Bachelors in Aerospace Engineering. During his studies, he worked on several research projects related to Aerospace Materials & Structures, Computational Fluid Dynamics, Nano-technology & Robotics. After graduating, he has been working as a freelance Aerospace Engineering consultant. He developed an interest in technical writing during sophomore year of his B.S degree and has wrote several research articles in different publications. During his free time, he enjoys writing poetry, watching movies and playing Football.

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