Applications of SEM
Applications of SEM
SEM is used broadly in many fields of research due to its versatility, and ability to magnify surfaces far beyond what optical microscopy can achieve. Browse some of the applications of SEM at the MCFP below.
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SEM enables researchers to look at the shape, roughness, or texture of surfaces. This is valuable when mechanical engineers are investigating how surface roughness leads to increased drag on aircraft or water vessels, or for physicists trying to understand how light may scatter from a poorly polished optical component.
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SEM can be very precise for measuring the dimensions of micro/nano-sized materials, such as electro-spun polymer fibres for water filtration, or nanoparticles used for catalysis.
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With careful sample preparation, SEM is used to investigate how mixed and layered materials behave, like investigating the interface between a carbon fibre and matrix in a composite, where electrolytes travel in novel battery materials, or the thickness of coatings.
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Provided tissues and cells are prepared appropriately, SEM can even investigate biological materials, studying how bacteria interact with novel antibiotics, how cells develop on nanostructured surfaces, and where soil contaminants end up in plants.
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SEM is more than just imaging, it can tell you about the elemental composition of materials as well, a technique called SEM-EDS. Here we can investigate where elements are located on a surface and within a structure, and even identify materials, like pigments used in a piece of artwork for example.
What are the Benefits and Limitations of SEM?
Clearly SEM is a powerful technique in research, but it is important to weigh up the strengths against some of the limitations.
Spatial resolution:
- Light microscopes are typically limited to ~200 nm
- Electron microscopes can achieve ~2 nm or better
Depth of field (focus):
- Resolution in light microscopy is usually achieved via confocal methods resulting in very narrow depth of focus
- SEM achieves high resolution while maintaining good depth of field
Specialised detection and analysis modes:
- The SEM can perform microanalysis where we can identify the elements/composition in a sample
- Multiple detectable signals mean we can achieve improved contrast for a broad range of samples
Samples must be vacuum compatible:
- Cannot image wet samples
- Samples must be dehydrated which can limit applicability or add unwanted processing steps
Samples should ideally be conductive:
- Insulating/non-conductive samples can be challenging to image in SEM
- Adds extra preparation steps
No colour!
- We are used to seeing the world in colour
- Comparing optical and EM images can be challenging
It is a surface-scanning technique, we cannot see through things
- We may be used to preparing samples under coverslips or imaging through coatings