Physicists were able to "photograph" individual atoms in record resolution

Physicists were able to "photograph" individual atoms in record resolution
Physicists were able to "photograph" individual atoms in record resolution
Anonim

An international team of scientists has perfected the ptychography method to get close to the physical limitations of its resolution. In the picture they received, individual atoms are visible, and few distortions are caused by their thermal vibrations.

Physicists were able to "photograph" individual atoms in record resolution

Having reached the limits of the resolution of modern measurement methods, the team of scientists worked under the direction of David A. Muller. It was this engineering professor from Cornell University (USA) who set the previous record in this field three years ago. An article describing the work of American, Swiss and German physicists is available in the journal Science of the American Association for the Advancement of Science (AAAS). Since the publication is closed, stunning images, most of which, unfortunately, are understandable only to professionals, can be viewed in the preprint of the scientific work on the arXiv portal.

Ptychography allows individual atoms to be distinguished more clearly than any other means, including atomic force and scanning tunneling microscopes. Most importantly, this method "looks" into the structure of the substance under study, and not just scans its surface. In a simplified way, the principle of ptychography can be described as follows. A slightly defocused electron or X-ray beam is directed at the sample. Behind the irradiated object there is a receiver on which an interferometric pattern of electrons or photons is formed.

Physicists were able to "photograph" individual atoms in record resolution

Analyzing the received signal, the computer restores the position of the atoms that have deflected photons or electrons. Despite all the improvements, the method still has some significant limitations. For example, the thickness of the sample under study does not yet exceed several tens of nanometers. The larger it is, the more powerful a computer is needed to analyze the signals and restore the picture, as well as the stronger the noise and distortion on it. However, Mueller's team is not discouraged and already envisions several ways to further improve the technology.

Physicists were able to "photograph" individual atoms in record resolution

In their last experiment, where they got close to the theoretical limit of ptychography, physicists used a beam of electrons directed at different angles to a thin PrScO3 crystal. The resulting images, which were obtained by scientists, clearly show the three-dimensional structure of perovskite, consisting of atoms of praseodymium, scandium and oxygen. For comparison, the work provides several illustrative examples of similar studies by other visualization methods.

As Mueller points out, his colleagues' job is like buying new glasses after always wearing very weak lenses. Scientists are now eager to use improved ptychography on a variety of objects - from semiconductor crystals (for finding flaws in them) to living neurons (for studying submolecular processes in the nervous tissue). In addition to expanding the list of samples that physicists are going to place under a new "microscope", they are thinking about expanding the capabilities of the method.

First of all, there is an obvious way to increase the resolution - to take a sample from as heavy atoms as possible and cool it to a temperature close to absolute zero. But if between the results of 2018 and the current work, the difference in picture clarity was almost two orders of magnitude, then cooling will no longer give such an increase.In addition, supercomputers and neural networks can be used to speed up the calculation of the data received by the radiation receiver. The latter improvement is unlikely to increase the resolution of the method, but it will allow scanning larger structures.

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