What is SEM?
A scanning electron microscope (SEM) is a device for observing the surface of samples on a nanometric scale.
It uses a beam of electrons to scan the surface and produce three-dimensional images. The SEM has many advantages over other observation techniques, such as the optical microscope or the transmission electron microscope, but it also has a few disadvantages that you need to be aware of and master.
Here are some of the disadvantages:
– SEM requires a high vacuum in the observation chamber, which implies the use of vacuum pumps and valves, as well as regular monitoring of the pressure level. The vacuum can be disturbed by leaks, contamination or outgassing of samples.
– SEM can damage samples, particularly those that are sensitive to electrons, such as organic or biological materials. Electrons can cause chemical reactions, structural changes, deformation or breakage. The beam parameters (current, voltage, diameter) must therefore be chosen according to the nature and fragility of the samples.
– SEM can induce artefacts or biases in images or analyses, due to various factors such as beam geometry, sample topography, detector type, signal processing or acquisition software. It is therefore important to be vigilant and critical when interpreting the results, and to compare them with other sources of data.
The SEM is therefore a powerful but delicate tool to use, requiring specific skills and ongoing training.
It is important to familiarise yourself with the principles of SEM operation, observation methods, analysis techniques and the precautions to be taken to obtain reliable and relevant images and information.
In this article, we give you some advice on how to maintain your SEM and optimise its performance.