At Empa’s Electron Microscopy Center, a new transmission electron microscope has recently been used that offers completely new opportunities for the physical and chemical analysis of very small samples. It can be used, for example, to observe the growth of nanocrystals in real time - and to record it on video.
Rolf Erni is enthusiastic about the latest instrument, which has been in operation at Empa’s laboratory facilities since the start of the year. The new transmission electron microscope (TEM), including all its the associated equipment, fills a whole room. Thanks to its higher resolution, the new TEM allows atomic-resolution chemical analysis and in-situ measurements, i.e. the real-time observation of processes such as chemical reactions. "That is what makes videos so valuable, because they show the precise progress of the reaction and not just a snapshot," says Erni.
Erni and his team have already carried out several in-situ experiments with the new TEM. The main aim of these was to observe the growth of nanoparticles in liquids. "We have already grown gold and silver particles in liquids and observed them in real time." Such investigations still represent relatively basic research, meaning that they are not very application-oriented. "However, they may become very interesting in future," says Erni, "for example, for looking at new battery materials in situ and then observing or controlling the electrochemical reactions." Ultimately, you have to start somewhere, yet it also paves the way for the future.
However, the new analytical capabilities of the TEM can also be used for electron holography, a method by which electrical and magnetic domains can be imaged with nanometer resolution. This not only allows samples to be examined better structurally and chemically, but also physically. The TEM is therefore particularly suitable for carrying out in-situ measurements on very small samples. "In the case of larger samples, a transmission electron microscope is not the right instrument. There are other methods that provide more statistically relevant results, such as chemical analysis methods," explains Erni.