How can atoms be photographed?
This article's featured image shows the highest possible resolution of the atoms in a crystal in the most amazing way possible. In order to obtain such an image, Cornell University researchers magnified a sample of a three-dimensional crystal 100 million times and doubled the resolution in order to record such an image.
But why photograph atoms to such an extent? Is it important and every day scientists are looking for new methods to get a picture of this world with greater clarity? The importance of imaging atoms is not limited to enriching human curiosity, but such images can be used to develop various materials for more powerful designs in phones, computers, and other electronic devices. Also, the existence of high-quality images of atoms of different materials can overshadow the future of batteries.
How can atoms be photographed?
The image ahead using a technique called "electron petchography" (electron ptychography) has been obtained. During this method, an electron beam hits a material considered as a target at a speed of about one billion per second! The fired electrons in these conditions move in a fraction of a second, so they hit (or in some cases pass through!) the target sample at slightly different angles and get excited before exiting.
Electron microscopes and electron petchography
It is interesting to know that years before this study, electron petchography It was only used to image very flat samples of materials with a thickness of one to several atoms. But new studies make it possible to photograph multiple layers with a thickness of tens to hundreds of atoms! In this regard, it should be emphasized that this method is suitable for materials scientists who usually determine the properties of samples with a thickness of about 30 to 50 nanometers (this value is smaller than the length of your fingernails that grew in one minute, but it is several times longer than the length that electron petichography in The past could take pictures!) is also very useful. The results of this study are an important advance in the world of "electron microscopes".
The standard electron microscope was invented in the early 1930s, and in a revolutionary event, it was possible to see things like the polio virus that are smaller than the wavelengths of visible light. It was realized for the activists of the world of science. But apart from the revolution that was created through the invention of such microscopes, you should know that this device faced a certain limitation that hindered the work for imaging. In fact, increasing the resolving power of the electron microscope required increasing the energy of the electron beams; This is problematic in the sense that higher energy to increase image resolution would seriously damage the target sample. On the other hand, in the petchography method, by using a detector, all the different angles that the beam can scatter at any position of the target can be recorded; Therefore, much more information can be obtained with the same wavelength and lens.
In the 1960s, researchers developed the petchography method to overcome the limitations of theoretical electron lenses, and in the 1980s, they brought it to the laboratory plant. But due to computational limitations, detectors, and the complex mathematics required, this technique was not practical for decades. Early versions of this imaging method using visible light and X-rays worked much better than early electron microscopes in imaging atomic-sized objects. Improvements in imaging methods with these methods continued until in 2018 a group of scientists was able to create an optimal detector for electron petchography in the laboratory!
Each dot in this image is a single molybdenum or sulfur atom formed from two overlapping atomic-thick sheets. Until 2018, these images were the clearest images of the atomic world and were recorded in the Guinness Book of Records.
These researchers were able to create two-dimensional samples with recreate this technique and produce what Muller (one of the leaders of this research team) calls the highest resolution image of any method in the world. The researchers created this feat using a lower energy wavelength than other methods, thus giving the world of science a clearer image with fewer limitations.
From 2D imaging to 3D imaging of atoms
As we mentioned earlier, in 2018, the image of atoms was only a two-dimensional example. In fact, the next challenge for physicists was to glaze with thicker samples! Because when faced with thicker targets, an electron wave bounced off many atoms before reaching the detector, in other words, the problem of "multiple scattering" was seen in thicker targets.
In order to solve this challenge. Using sufficient overlapping patterns and high computing power, the researchers were able to reverse engineer the arrangement of atoms that follow a specific pattern and obtain the original pattern. In general, such high-resolution imaging techniques are essential for the development of the next generation of electronic devices, as, for example, many researchers seek to find more efficient semiconductors beyond silicon-based computer chips. So this path could be a highway to the future!
Feature image: Electron petechography reconstruction of a crystal of praseodymium orthoscandate (PrScO3) created at 100 million times magnification.
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Source: SCIENTIFIC AMERICAN