Solving the microstructure of materials is essential for uncovering the origin of their functionalities and can accelerate material innovations. The electron microscope is one of the most powerful tools for measuring the arrangement of atoms in materials. It is not only widely used in physics, chemistry, material science, and biology, but also used in device quality diagnosis in the semiconductor industry. The advancements of electron microscopy techniques have led to numerous scientific breakthroughs.
Zhen Chen, now Associate professor at Tsinghua University, and previously a postdoctoral fellow at Cornell University, has devoted himself to the research of new quantitative microscopy imaging technology for a long time, focusing on breaking through the resolution limits of existing imaging technology, expanding the application range of imaging technology, and solving more material structure problems.
By developing a new ptychography technique, Chen achieved a new resolution record of 0.02 nanometers in imaging single atoms. This breaks the resolution limit of the best physical lens by 2 times. This new technique can also be used for low-dose imaging and accurately measuring the atomic position of all elements including the lightest hydrogen atoms. It is worth mentioning that the previous world record in imaging resolution, adopted as the new Guinness World Records, was also made by Chen and his colleagues.
Prior microscopes were all limited in various ways by the optics of the microscope itself. Chen’s work achieves such a high resolution that for the first time the resolution of his images is limited by the thermal vibrations of the atoms themselves. The blur in the image is caused by the random thermal motion of the atoms themselves, rather than the resolution being not high enough. This means that this level of resolution is close to the limit that can be achieved at room temperature.
Chen had overcome several technical challenges to break the resolution limit, including developing novel mathematical algorithms to solve an inverse problem of multiple scattering that has plagued the microscopy field for nearly a hundred years. This led to the lattice-vibration-limited resolution, and more importantly, the reconstruction of the three-dimensional structure of samples. The work was acknowledged as the “culmination of a long quest in electron microscopy community."
In the future, Chen hopes to develop new techniques for three-dimensional atomic structure and magnetic structure, explore low-dose imaging and accurately determine the atomic positions of all elements, including the lightest hydrogen element, to explain physical and chemical phenomena that are currently incomprehensible, and to potentially solve some key material science issues.
