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Overcoming Challenges of Imaging Non-Conductive Samples in Electron Microscopy [SEM Technical Note]

In standard high-vacuum electron microscopy, accurate imaging of non-conductive materials poses difficulties due to charge accumulation and overexposure. Typically, a conductive coating is applied to aid in grounding, but what if coating the sample is undesirable?

 

Introducing Low-Vacuum SEM

Low-vacuum electron microscopy that effectively mitigates charge build-up on insulating samples without requiring any special pretreatment. By allowing a controlled amount of atmospheric gases into the chamber, additional pathways for electrons to escape the specimen are created. This approach not only prevents charge accumulation but also enables higher resolution imaging by allowing a higher e-gun voltage to be applied to the insulating specimen.

Low-Vacuum SEM Effectiveness

To demonstrate the effectiveness of Low-Vacuum SEM, consider the example of a pine wood sample.

Under standard conditions, the sample quickly accumulates charge and suffers beam damage even within seconds of exposure to a 10kV accelerating voltage.

However, when imaged under low-vacuum conditions, the pine wood sample exhibits no charge accumulation, resulting in improved contrast and finer details, thanks to the application of a higher energy 20kV beam and reduced charge accumulation.

Additional Low Vacuum Images & Applications

Here is an example of a paper towel imagied with High Vacuum, and no coating

Here is the same example imaged High Vacuum, and coated with a thin layer (5nm) of gold

Here is the same sample imaged at Low Vacuum showing a more detailed clearer image.

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