The environmental scanning electron microscope and its applications

Area of Science:

• Materials Science
• Microscopy
• Environmental Science

Background:

• Traditional scanning electron microscopy (SEM) requires high vacuum, limiting the observation of hydrated or volatile samples.
• Environmental scanning electron microscopy (ESEM) allows imaging under non-vacuum conditions, but further improvements are needed for enhanced sample handling and detection.

Purpose of the Study:

• To develop an improved environmental scanning electron microscope (ESEM) capable of imaging wet specimens at high frame rates.
• To enable the observation of dynamic processes and biological samples in their native states.

Main Methods:

• Incorporation of a pressure-limiting aperture below the objective aperture with independent pumping.
• Tilting of the pressure-limiting aperture to manage gas flow and prevent column contamination.
• Detection of backscattered and multiple-backscattered electrons below the pressure-limiting aperture.

Main Results:

• Successful observation of wet specimens, including live seedlings, ants, and fresh rat tissues, at 7kV and TV rates.
• Demonstrated capability to examine samples across the full pressure range (0-1013 mbar).
• Observed phenomena such as salt crystallization, wool fiber treatments, and radiation effects.

Conclusions:

• The developed ESEM design facilitates high-resolution imaging of hydrated samples under various pressures.
• The system's ability to observe dynamic processes opens new avenues in biological and materials science research.
• Future developments require collaboration between manufacturers and researchers to advance ESEM capabilities.