An electron microscope is an imaging equipment based on the flow of electrons and very thin samples. It is an expensive equipment and requires trained operators. It makes use of electrons who, owing to their small size, can pass through (or be absorbed by) the samples. A beam of electrons is formed and controlled through an electromagnetic field and is focused on thin samples. The transmission electron microscope (TEM) detects the electrons that pass through the sample and form a high resolution image of the sample. A scanning electron microscope (SEM) detects the secondary electrons excited by the primary electrons and obtains a surface image. A combination of the two, scanning transmission electron microscope (STEM) makes use of both the transmitted and excited electrons to generate high resolution images. Further enhancements can be added to these microscope for specific studies such as detection of elements and chemical characterization (by SEM-EDX). Resolution of up to 0.1 nm and magnifications of up to 5,00,000 times can be achieved by these microscopes.
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