How does an environmental scanning electron microscope differ from a conventional scanning electron microscope?

The primary difference between an environmental scanning electron microscope (ESEM) and a conventional scanning electron microscope (SEM) lies in the environment required for operation. While a conventional SEM requires a hard vacuum to function, an ESEM can operate in a gaseous atmosphere, such as air, water vapor, nitrogen, argon, or oxygen.12

This fundamental difference leads to several practical distinctions:

• Specimen Preparation: Conventional SEMs often require specimens to be coated with a conductive material, such as gold, to prevent charging and ensure a clear image. In contrast, the ESEM eliminates the need for such special preparation.13
• Sample Versatility: Because the ESEM does not require a hard vacuum, it is capable of examining moist specimens and even living organisms, such as arthropods.12
• Dynamic Observation: The ESEM allows researchers to observe dynamic phenomena in real-time, including wetting, drying, melting, freezing, crystallization, and corrosion, often by utilizing a mechanical substage that allows for temperature control and the addition of liquids.1

The ESEM achieves this through a specialized secondary electron detector that relies on gas ionization to amplify the signal and neutralize surface charges on the specimen.1