Can atoms be seen?

The answer is yes, the atoms can be visualized at present, through scanning electron microscopes based on the tunnel effect and atomic force microscopes. These different techniques will be described in this publication.

Microscopy

Tunnel Effect Microscope

Heinrich Rohrer and Gerd Binnig in 1981 were the ones who developed the electron microscope based on the tunnel effect, receiving the Nobel for it in 1986. This microscope could be defined as a machine capable of revealing the atomic structure of the particles, applying the technique that is known also as "tunnel scanning" which is associated with quantum mechanics. The technique used is based on the ability to trap the electrons that escape in this tunnel effect, to achieve an image of the atomic structure of matter with a high resolution, in which each atom can be distinguished from another. Once the process has been carried out in the microscope, scanning the surface of the object and making a map of the distance between several points, a three-dimensional image is generated. In 1989 IBM managed to move atoms individually for the first time, with the "Tunneling Microscope" (STM-Scanning Tunneling Microscope). In 1990 they published the famous image of its logo formed by atoms of xenon on nickel.

IBM logo made with xenon on nickel. Credit: IBM. Image originally created by IBM Corporation.

Atomic Force Microscope (AFM)

On the other hand, a newer and more precedecessive technique of the tunneling microscope is the Atomic Force Microscope (AFM), which uses the information obtained when the electrons it emits are repelled by the electronic clouds of the atoms of the surface. Scientists from the IBM laboratory in Zurich, Switzerland, would achieve a milestone in the field of nanotechnology and molecular electronics by visualizing a molecule of pentacene (C22H14), which consists of five benzene rings linked together to form an aromatic chain.

Molecule of pentacene (C22H14)

This achievement was published in the journal Science, where researchers have also discovered that the repulsive force that has allowed them to obtain enough contrast for the image comes from the quantum effect called the Pauli exclusion principle. In recent years, it had been possible to define nanostructures at the atomic scale and now it has been possible to show the chemical structure of a molecule with an atomic resolution, seeing the individual atoms.

How we can see in this post, there are currently many ways to see atoms through electron microscopes and atomic force, which is undoubtedly has generated great progress in the field of nanotechnology and nanoscience.

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References

Paredes, J. I., Villar-Rodil, S., Solís-Fernández, P., Martínez-Alonso, A., & Tascon, J. M. D. (2009). Atomic force and scanning tunneling microscopy imaging of graphene nanosheets derived from graphite oxide. Langmuir, 25(10), 5957-5968. ISO 690.