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Ptychography marvels

Electron ptychographic reconstruction of a praseodymium orthoscandate (PrScO3) crystal, zoomed in 100 million times.’ Image and caption credit: Cornell University, 2021.

I love macrophotography, doing a bit myself and keeping track of the many wonderful photos taken by real “artists”. In the last 10 years macrophotography has progressed enormously thanks to … software. It is both the software supporting the design and production of better lenses but most importantly the software used to convert what the lenses capture into an image. Stacking has changed macrophotography making it possible to see the very very small at an unprecedented level of detail by making sense of each pixel and staking pixels captured by hundreds of shots.

This technology is being applied to go further into the atomic scale. Rather than aiming for perfect focus you take many shots and then you combine them together. At Cornell University a team of researchers have been able to take photos (using an electron microscope) of materials at the atomic level. Two years ago they captured the atomic distribution of two layers of molybdenum disulfide -each layer one atom deep-, now they have perfected the software (and the equipment) to achieve an even better resolution of the atoms location in a crystal lattice (see photo).

In the photo you can clearly see the individual atoms, bright yellow dots, and how they cluster. The red halo is still the atom: although we usually visualise an atom as a tiny marble around which electrons are orbiting the reality is quite different. An atom is a field, likewise the electrons, what we are capturing is the intensity of this field that rapidly fades away as we move further away from the “nucleus”. This fading is clearly visible in the photo at the very edges of the red halo whilst the halo itself is the result of the jiggling of the atoms (their temperature….).

This type of macrophotography, and technique, is called ptychography. It is obviously of interest to academics but it can also have practical application, according to the researchers, to detect impurity in the preparation of semiconductors, particularly those used in quantum chips.

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the Industry Advisory Board within the Future Directions Committee and co-chairs the Digital Reality Initiative. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.