A scientific instrument that uses the electron beams to study an object or specimen to generate a large image is called as an electron microscope (EM). These types of microscopes focus the electron beam on an object by using electromagnetic coils instead of glass lenses since the electrons are not capable of passing through the glass. The image magnification is limited in a light microscope while the electron microscope allows you to look into every object in detail. Electron microscopes have evolved over time and different types of microscopes have been developed for scientists to observe and investigate various aspects of an object in detail. Some of the specialized types of electron microscopes are as follows.
Transmission Electron Microscope (TEM)
The transmission electron microscope is the first electron microscope to be developed by scientists. A beam of electrons are sent towards an object and the images are recorded immediately once it passes through a thin slice of an object. Some electrons may get reflected while some may pass through the object. The electrons that pass through the object is identified and is used to create and specimen of the image. The beams travel through a lens piercing through the object before it gets collected onto a screen. They produce the largest magnification among all the types of microscopes. It is used to learn the components of a cell, such as organelles and their structure. The main drawback of TEM is the need for thin slices of the specimen. The TEM is extensively used in nanotechnology, for semi-conductor analysis and production. They are used in practical applications in the field of chemistry, metallurgy, and gemology.
Scanning Electron Microscope (SEM)
Along with the transmission electron microscopes the scanning electron microscopes are extensively used in the field of science. The SEM lets us see the surface of three dimensional specimens in very high resolution. They are 10 times less powerful than the TEM, but produce sharp, high resolution, black and white images. It scans the surface of an object with focused electron beams by identifying electrons that are reflected and deflected from the surface of an object. Small objects like insects can be viewed on SEM without losing the focus even on low magnifications making it one of the best electron microscopes for generating three dimensional images. SEM is also used to provide information on morphology, and topography.
Reflection Electron Microscope (REM)
In terms of structure the reflection electron microscope works much similar to the SEMs. Here, the reflected electrons are detected and gathered to study the surface of the specimen object. The REMs are usually grouped with spin polarized and low energy electron microscopes to image the specimen structure.
Scanning Transmission Electron Microscope (STEM)
Just like the traditional TEMs, the scanning transmission electron microscopes pass an electron beam through a very thin slice of an object. The STEM focuses on the beam that passes beforehand and constructs an image through raster scanning, instead of focusing on the beam after passing through the object. It is a combination of high magnification of TEM and better surface detail of SEM. STEM is usually used to perform very complex analysis of objects and specimens that is not possible by just using the TEM.
The electron microscopes are one of the most powerful microscopes available today allowing scientists to view the images at nanometer sizes. They are large and costly; require maintenance, extremely sensitive to vibration and magnetic fields. Despite these disadvantages electron microscopes are a huge asset for research based laboratories.