The laser pointer beam can be used to change the properties of materials in an extremely precise way. This principle has been widely used in technologies such as rewritable DVDs. However, the basic process is generally carried out at such an unimaginable speed and such a small scale that it has not been directly observed so far. Researchers from the University of Göttingen and the Institute of Biophysical Chemistry (MPI) in Göttingen have now successfully photographed the laser pointer transformation process of a crystal structure with nanometer resolution and slow motion in an electron microscope for the first time. The results have been published in the "Science" magazine.
The team includes professors. They took advantage of the unusual properties of a material composed of a thin atomic layer of sulfur and tantalum atoms. At room temperature, its crystal structure is twisted into tiny wave-like structures-forming charge density waves. At higher temperatures, a phase change occurs, and the original microscopic waves suddenly disappear. Electrical conductivity will also change dramatically, which is an interesting effect for nanoelectronics. In the experiment, the researchers used a short laser pulse to induce this phase change. And recorded the charge density wave response of the film. The first author from the University of Göttingen explained. What we have observed is the rapid formation and growth of tiny areas where the material is switched to the next phase. The ultrafast transmission electron microscope developed by Göttingen provides the highest time resolution in the world for this imaging.