Image Credit: Courtesy of UCLA
Scientific Frontline: "At a Glance" Summary
- Main Discovery: A new computational framework establishes a benchmark for determining the three-dimensional positions and elemental identities of individual atoms within amorphous, disordered materials like glass.
- Methodology: Researchers combined atomic electron tomography (AET) and ptychography with advanced algorithms to analyze rigorously simulated electron-microscope data, accounting for image noise, focus variations, and atomic thermal vibrations based on quantum mechanical models.
- Key Data: The study demonstrated 100% accuracy in identifying silicon and oxygen atoms within amorphous silica nanoparticles, achieving a positional precision of approximately seven trillionths of a meter.
- Significance: This advancement overcomes the historical limitation of 3D atomic imaging being restricted to crystalline structures, enabling the precise characterization of non-repeating, disordered solids for the first time.
- Future Application: The technique supports the development of advanced materials for ultrathin electronics, solar cells, rewritable memory, quantum devices, and potentially the biological imaging of life-essential elements like carbon and nitrogen.
- Branch of Science: Nanotechnology, Materials Science, and Computational Physics.
- Additional Detail: The research appears alongside a complementary study in the journal Nature, signaling a major shift in the ability to visualize matter at the atomic scale without relying on averaging repeating patterns.
Researchers at the California NanoSystems Institute at UCLA published a step-by-step framework for determining the three-dimensional positions and elemental identities of atoms in amorphous materials. These solids, such as glass, lack the repeating atomic patterns seen in a crystal. The team analyzed realistically simulated electron-microscope data and tested how each step affected accuracy.
The team used algorithms to analyze rigorously simulated imaging data of nanoparticles — so small they’re measured in billionths of a meter. For amorphous silica, the primary component of glass, they demonstrated 100% accuracy in mapping the three-dimensional positions of the constituent silicon and oxygen atoms, with precision about seven trillionths of a meter under favorable imaging conditions.
While 3D atomic structure determination has a history of more than a century, its application has been limited to crystal structures. Such techniques depend on averaging a pattern that is repeated trillions of times.
In contrast, the precision and accuracy required to map individual atoms in a single, non-repeating structure have been out of reach until recently. Imaging amorphous materials in 3D at the atomic level is expected to have such a widespread impact on science and engineering that this UCLA study appears back-to-back with another paper on the same topic in the journal Nature.
The study focuses on two imaging techniques developed over the last 25 years by corresponding author Jianwei “John” Miao, a professor of physics and astronomy in the UCLA College.
One is atomic electron tomography, or AET, which takes many images from different angles as an electron beam passes through a sample, then uses computation to reconstruct a three-dimensional map of the atoms. The other is ptychography, a computational microscopy technique that records patterns of scattered electrons as a tightly focused beam scans a sample and uses algorithms to reconstruct an image without the need for a physical lens.
To validate their approach, the researchers used rigorously simulated AET and ptychographic data that closely mimic real experiments. Their algorithms had to contend with sources of error such as image noise, small variations in focus and vibrations of atoms caused by ambient temperatures. All of these factors were incorporated into electron scattering simulations based in quantum mechanics, the counterintuitive rules that govern subatomic particles. The computation also took advantage of known constraints, such as the types of atoms present and the typical distances between neighboring atoms, to refine the final 3D atomic map.
As a rule, algorithms typically gain power over time from improvements in programming and hardware. So computational microscopy, including AET and ptychography, is poised to provide a long-lasting boost to 3D atomic imaging. What’s more, unlocking the 3D structure of amorphous materials is expected to drive both technological innovation and new insights into fundamental aspects of nature.
For example, glass has an amorphous structure and happens to be one of the most ubiquitous and useful materials on the planet. Emerging technologies for ultrathin electronics, solar cells, rewritable memory, medical devices and quantum technologies often rely on materials that also lack long-range atomic order. In the future, biologists could gain access to 3D imaging once advances make it possible to identify individual carbon and nitrogen — atoms that are essential to life, and the close neighbors of oxygen in the periodic table, the element mapped alongside silicon in this study.
Funding: The study was supported by STROBE — a National Science Foundation Science and Technology Center for which Miao serves as deputy director — and the U.S. Air Force Office of Scientific Research.
Published in journal: Nature
Title: Accurate determination of the 3D atomic structure of amorphous materials
Authors: Yuxuan Liao, Haozhi Sha, Colum M. O’Leary, Hanfeng Zhong, Yao Yang, and Jianwei Miao
Source/Credit: University of California, Los Angeles | Wayne Lewis
Reference Number: nt012826_01
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