by Vincent Wuelfrath,
PhD candidate at Polytechnique School of Montreal
We are in the year 1609. The great astronomer Galileo Galilei has heard of a device that allows the user to see extremely small objects as if they were much larger – the magnifying glass. He drew inspiration from this discovery and created the first telescope so he could study the sky. With this device, he could observe extremely large objects such as stars and planets that are millions of
Through the years, the maximal resolution of light microscopes kept improving and the quality of the images was getting better. However, there was a limitation to this device. Optical microscopes work using the visible light. Visible light is a wave and it is physically impossible to observe an object that is significantly smaller than that wave. This means that we can’t observe objects that are less than about 200 nanometers, or 0.0002
Now we move forward to the year 1931. Two German scientists, Max Knoll and Ernst Ruska, have successfully produced an image using electrons instead of visible light. To do so, they had to thank J.J. Thompson that discovered the electron back in 1897 and Hans Busch that discovered in 1927 that electrons could be focused using a magnetic field, much like light can be focused using a glass lens. Now, scientists all over the world had a device that could potentially achieve a far better resolution than a light microscope and let them observe the smallest objects. For his discovery of the transmission electron microscope (TEM), Ernst Ruska was awarded a Nobel Prize in 1986. Furthermore, this discovery has led to the development of another type of microscope in 1942 – the scanning electron microscope (SEM).
Nowadays, in a world where nanotechnology finds more and more applications, the electron microscope has become an indispensable tool for engineers, scientists and inventors. It is now possible to observe objects that are 0.05 nanometer in size, much smaller than an individual atom (see Fig. 1). It is sometimes difficult to really appreciate how something so small can have such a big impact on our lives. But considering that everything around us is made of the same raw material, the atom, it is clear that getting a clear view of this object that used to be invisible is an incredible step for science. We now have to wait and see what secrets are hidden in the nanosized world.