A transmission electron microscope, also known as TEM, is a type of microscope. These microscopes use a particle beam of electrons to generate a microscopic, or magnified picture. This method of magnification can magnify the objects around, or up to, 2 million times.
This is so valuable in research as it can show you images that are so small, magnifying details and teaching us lots about certain things. It is specifically useful in the biological field.
Read on for more information about the transmission electron microscope, its uses and its advantages and disadvantages.
Transmission Electron Microscope
TEM works by using moving electrons to provide this information on samples. They are the most powerful microscopes out there.
They create very clear and extremely magnified images of up to 2 million times magnification. These microscopes have created a world of difference to education, scientific research and industry applications.
TEM telescopes function in a similar way to a regular microscope, except they replace a few of the key features. These microscopes use electrons instead of photons.
They also replace electromagnetic lenses with glass lenses. This microscope then shows the magnified image on a screen and not through the eyepiece like most other microscopes.
TEM microscopes are made up of the following features which come together to make the fantastic microscope:
- An electric beam
- Lenses that are electromagnetic
- A source of moving electron
- A thermionic gun
- A computer
- Phosphor screen
- Vacuum chamber
- Condensers (usually 2)
How Does A TEM Work?
TEms use an electron beam to produce their image. This electron beam has to be of a very high voltage. These electrons are shot out at the top of the microscope and they travel through the microscope using the vacuum tube.
The electromagnetic lens then gathers and focuses these electrons, creating a very fine beam. This is where the microscope greatly differs from others of its kind. Usually, a glass lens would be used here.
Then, the beam will pass through the object that you are hoping to look at. The specimen should be very thin.
Here, the electrons that do not hit the object will scatter, while the others will hit the fluorescent screen that is located at the bottom of the microscope.
An image of the specimen will then show on the screen. It will show up in different shades depending on the density of the object.
History Of Transmission Electron Microscopes
Ernst Ruska was the man who created the very first TEM microscope, which is also the very first electron microscope. He created it alongside Max Knolls in 1931.
Over the 30’s, these men improved the quality of the magnification and the amount of times it magnifies.
Ruska then took his idea to a company where he became an electrical engineer who helped to manufacture these microscopes on a bigger scale.
Imaging
These TEM microscopes produce fantastic images of their samples at such a zoomed in rate.
These images are high resolution and so are very clear. Black and white images are created from this microscope, as the image comes out in shades depending on the density of the object.
This image is created from the interaction between the electrons that travel through the microscope in the vacuum chamber, and the prepared samples.
The vacuum chamber is an area of the microscope that air is pumped out of. This creates a vacuum and these electrons are then able to move within the vacuum.
The electrons then pass through the electromagnetic lenses that are placed throughout the vacuum chamber.
The beam which is created by the electrons will pass through these electromagnetic lenses and will then hit a screen where the electrons will convert into light and form an image on the screen.
You can alter the magnification of the microscope by changing the voltage of the electron gun, which controls the speed at which the electrons travel through the vacuum.
This will change the wavelength of the beam and mean that the image will be different at the end.
The image will then appear on the screen due to the coils.
Just to clarify, the speed that the electrons move relates to the quality and detail of the created image. If the electrons are moving quickly, then the wavelength will be shorter and the image will be of better quality and detail.
The lighter areas that show on the image represent the larger number of electrons that were able to pass through the object there. That means that area is less dense. The darker areas show the denser parts of the objects.
These microscopes were a game changer when it came to research on the shape and size, structure and texture of specimens.
You can’t look at any object through a TEM microscope. They must be very thin samples to allow any electron to pass through them.
They also need to be strong enough to withstand the vacuum chamber and they will need to be properly prepared before they are viewed through the microscope.
This preparation could include sectioning, staining or dehydration as well as many more.
What Are TEM Microscopes Used For?
Transmission Electron Microscopes are perfect for use in lots of different fields. They create such detailed and magnified images of the sample.
They have been used in medical research as well as research into nanotechnology. They have often been used in biological research and forensic research.
They are also used in life sciences, education, gemology and industry. The ability to analyze the structure and texture of samples in such detail has meant that the information is very useful when studying crystals.
Differences Between TEM And Light Microscopes
TEM and light microscopes use the same principles to work, but they are not the same in any respect. They have lots of differences. TEM electrons use electrons to magnify their images instead of using light.
The light microscopes can only magnify for up to 2000 times because it can only be magnified depending on the wavelength of the light.
Electron microscopes are magnified depending on the beam of electrons and so can produce much more magnified images with a great resolution.
Advantages Of TEM
A TEM microscope has many advantages over other types of microscopes. These advantages are:
- TEMs magnify up to 2 million times. This is the most powerful magnification of any microscope available. This is due to the use of electrons in the microscope.
- TEMs have been groundbreaking for research and developments in so many different areas, including science, education and industry. They are very useful int he study of crystals.
- They produce very high quality and detailed images.
- They have been very useful in creating information on shape, size and structure as well as many other features.
- They are easy to use when you understand how they work.
Disadvantages Of TEMs
No object is perfect, and the TEM is no exception. Below are the disadvantages of Transmission Electron Microscopes.
- They are very big to store and so are difficult to have anywhere but in a lab.
- They are very expensive to buy.
- The samples have to be prepared a certain way and in a lot of detail.
- You have to know how to operate the microscope before you use it, which means you may need to be trained to know how to use it.
- Your samples have to be electron transparent.
- The images on this microscope are black and white.
- They require a lot of upkeep and have to be stored in an area that does not have vibrations or electromagnetic fields.
Preparing The Specimen
A TEM specimen must be small enough and thin enough to allow the electrons to pass through it. This is very important as you will not get an image if this is not able to happen.
There is a process that all of the samples need to go through before they can be viewed which is called dimpling.
This is a technique where the sample is thinned in the middle but left thicker on the outer surface to allow you to handle the specimen easily.
You will then have to perform ion milling on the specimen, where charged ions are placed on the specimen surface by applying a high voltage to them. This will remove any material that has landed on the surface.
Frequently Asked Questions (FAQ’s)
How Much Do Transmission Electron Microscopes Cost?
These microscopes are very expensive, with prices usually around $100,000 for a new model. They are very expensive and large instruments and so need storage and will need to be maintained often.
They are the most powerful microscopes available as they magnify to such a level and they create such high resolution, detailed images. They have been so useful in research.
They are very expensive products and so are usually only found in official labs and research centers. The light microscopes are much more commonly found.
Who Discovered The Transmission Electron Microscope?
This microscope was invented by Ernst Ruska and Max Knolls. It was created in 1931. It was the first electron microscope and it allowed researchers and scientists to view their specimen at a magnification of up to 2 million times.
This microscope was a fantastic invention. Ruska then went on to help with the manufacturing of these microscopes later in the 1930’s after he had fine tuned the design.
Final Thoughts
Now you have all the information you need to understand the Transmission Electron Microscope. TEMs have been revolutionary when it comes to research in many different fields.
There are many advantages of this fantastic technology, but there are also some disadvantages.
Ever since I was a little girl, I have been fascinated by science. Every holiday I would ask for the newest science kit, and spend weeks learning with it.
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