Scanning electron microscopy, or SEM, generates detailed, magnified images of an object by scanning its surface and creating a high resolution image.
SEM does this with a concentrated beam of electrons. The generated photos provide information about the object’s composition and physical characteristics. A scanning electron microscope is used to collect information about composition and topography.
SEM is a practical and helpful technique with many applications across multiple industries and sectors. It can examine both man-made and naturally occurring materials.
What Happens During SEM?
Scanning electron microscopy involves scanning a sample using electron beams. An electron gun discharges these beams, which then accelerates down the scanning electron microscope’s column.
During this process, electron beams pass through a succession of lenses and apertures that serve to focus them.
Under vacuum conditions, molecules, and atoms in the microscope column do not interact with the electron beam.
This provides high-quality imaging.
The vacuum also shields the electron source against vibrations and noise.
The electron beams scan the sample in a raster pattern, crossing the surface in lines from side to side and top to bottom.
Electrons interact with atoms on the sample’s surface. This contact generates signals specific to the sample in the form of secondary electrons, backscattered electrons, and rays.
The microscope’s detectors take up these signals and produce high-resolution images that are shown on a computer screen.
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Which SEM Microscope is Right for Which Application?
SEMs come in a lot of different types. The most common type uses a tungsten filament as an electron source. Another type is more specialized and has a field emission (FE) electron gun that makes the images clearer and bigger. Many things affect how you choose the best SEM lab.
Here is a list of some of the most important things to consider when choosing a SEM.
- Type of Sample: As mentioned, SEM can examine both man-made and natural objects. However, the type of SEM that will work best can vary depending on the subject being studied. For instance, biological samples might need a low-vacuum or outdoor SEM to prevent drying out.
- Needs for Resolution: The amount of resolution that different types of SEMs can achieve is not the same. If high-resolution photography is important for the job, a FESEM would be better than one with a tungsten filament electron source.
- Magnification Range: Just like resolution needs are different for each type of SEM, magnification ranges are also different. Lower magnifications may be enough for some tasks, but higher magnifications may be needed for more thorough analysis. When choosing an SEM, it’s important to think about the zoom range.
- Sample Size: The size of the sample being studied can also affect which SEM to use. Large samples may require a larger chamber or stage, while smaller samples may be better suited for tabletop SEMs.
- Budget: The budget is an important consideration for any instrument. Usually, SEMs with more features and better resolution will cost more. It’s important to examine the budget and decide which features are most important for the application.
Beyond these considerations, it’s crucial to seek advice from industry experts and thoroughly assess the technical specifications before choosing an SEM instrument.