The Science of the Very, Very Small

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Nanoscience is often described as the microscope of science. It delves into the very building blocks of life, focusing on the understanding and manipulation of materials and phenomena at the nanoscale. Nanotechnology, an application of this science, combines elements of physics, chemistry, biology, engineering, and materials science to explore the unique properties and behaviors of materials at this incredibly small scale.

One particular example of this is the scanning tunnelling microscope. Unlike a typical microscope, the scanning tunnelling microscope (STM) can probe the atomic structures of surface materials, as well as manipulate single atoms. This concept first emerged during the early 1980s, when it was invented by IBM scientists Gerd Binnig and Heinrich Rohrer. In 1986, this groundbreaking discovery led them to earn the Nobel Prize in Physics, opening up the world to breakthroughs in materials science, molecular chemistry, quantum mechanics, and more (Oxford).

The way these machines can study atoms is through the quantum mechanical phenomenon known as tunnelling (Britannica). Disrupting the rules of classical physics, electrons can, essentially, jump energy barriers and “tunnel” to regions of a surface material where they shouldn’t be able to appear. As the distance from the surface increases, the likelihood of detecting these rule-breaking tunnelling electrons decreases exponentially. The STM takes advantage of this; by using its extremely fine tip, the microscope is positioned just a few angstroms (10-10 m) above the surface (Britannica). Then, an electric potential difference is applied between the tip and the surface sample, and electrons from the sample are tunneled to the tip. The small electric current produced by the tunneled electrons – the lesser the distance, the higher the tunneling current is – is amplified and sent to the computer. Based on the recordings of the tunneling current, we can discover information about the surface material, from studying the chemical reactivity of atoms to examining quantum mechanical phenomena.

Probing for information isn’t all the STM can do. The manipulation of atoms has not only led to scientific discoveries but also made way for a new type of art—the creation of atomic structures.

Perhaps the most popular method of STM atom manipulation is lateral manipulation. This technique involves the creation of a temporary atom-tip attractive force between the atoms on the probe tip and the adatom, or the atom lying on the surface. With the force in place, the atom is then moved across the surface to a new position (Celotta et al). Finally, the STM tip is withdrawn to a point where the force between the adatom and the tip is negligible, leaving the atom bound to the final location on the surface, as shown in the diagram below (Eigler & Schweizer).

The first instance of lateral manipulation was used to position individual xenon atoms on a single-crystal nickel surface, building the “IBM” company logo (Eigler & Schweizer). Since then, IBM has expanded: holding the Guinness World Records record for the World's Smallest Stop-Motion Film is the movie “A Boy And His Atom,” where IBM researchers moved carbon monoxide molecules frame-by-frame to create a 1-minute film – which can only be seen because the video is magnified 100 million times. This movie consisted of a boy dancing around with his atom, playing basketball, tennis, and jumping on a trampoline of atoms. Filled with laughter, joy, tears, and awe, this movie was definitely ahead of its time (IBM).

At the time, IBM researchers were manipulating atoms to explore the limits of data storage (IBM). However, there are countless more applications to this aspect of nanotechnology. Different types of STM manipulation techniques are used to discover chemical reaction pathways, construct quantum structures, and use information about natural systems such as photosynthesis for solar energy utilization (). Standing at the forefront of nanotechnology, scanning tunneling microscopy continues to inspire further innovations in the science of the very, very small.

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References

Celotta, R. J., Balakirsky, S. B., Fein, A. P., Hess, F. M., Rutter, G. M., & Stroscio, J. A. (2014). Invited Article: Autonomous assembly of atomically perfect nanostructures using a scanning tunneling microscope. Review of Scientific Instruments, 85(12), 121301. https://doi.org/10.1063/1.4902536 

Eigler, D. M., & Schweizer, E. K. (1990). Positioning single atoms with a scanning tunnelling microscope. Nature, 344(6266), 524–526. https://doi.org/10.1038/344524a0 

Oxford Instruments. (n.d.). Scanning Tunneling Microscopy (STM). Retrieved from https://afm.oxinst.com/modes/scanning-tunneling-microscopy-stm 

The Editors of Encyclopaedia Britannica. (n.d.). Scanning tunneling microscope. In Encyclopædia Britannica. Retrieved from https://www.britannica.com/technology/scanning-tunneling-microscope

YouTube. (n.d.). Single Atom Imaging with a Scanning Tunneling Microscope. Retrieved from https://www.youtube.com/watch?v=oSCX78-8-q0