Laser-less TEM provides time-resolved images of cyclical phenomena

Many methods allow transmission electron microscopes (TEMs) to produce time-resolved images with atomic resolution. Extending the temporal resolution of TEMs beyond the nanosecond timescale, however, has only been achieved thus far by adding a laser, which releases electrons in precisely timed pulses instead of a continuous beam, allowing observations of fast dynamic phenomena.

But the combined cost of a laser and a new laser-compatible TEM is expensive. In an effort to make time-resolved TEM more accessible, Lau et al. invented a laser-less modification that grants existing TEMs the power of temporal resolution.

In lieu of a laser, the authors borrowed technology from accelerator physics, installing a radiofrequency beam chopper in the path of the microscope’s electron beam. The beam-chopping technology is contained in an easily retrofitted module located immediately after the electron gun.

“In principle, you can take any transmission electron microscope that’s in service, insert this box, and turn it into a time-resolved microscope,” said author June Lau. Compared to lasers, this technology saves money because users won’t have to buy a new microscope and detectors. It also accesses dynamics on a different time scale.

The beam chopper produces electron pulses between 80 megahertz and 12 gigahertz, which gives a temporal resolution in the nanosecond to picosecond range. This range is well suited for studying periodic phenomena, such as ferromagnets, memristors and batteries.

The authors built their prototype and proved that it works by imaging a microelectromechanical system sample. Next, they will refine their instrument. They are currently seeking samples from collaborators.

“Now we want to actually answer some science questions with our new invention,” Lau said.

Source: “Laser-free GHz stroboscopic transmission electron microscope: Components, system integration, and practical considerations for pump–probe measurements,” by June W. Lau, Karl B. Schliep, Michael B. Katz, Vikrant J. Gokhale, Jason J. Gorman, Chunguang Jing, Ao Liu, Yubin Zhao, Eric Montgomery, Hyeokmin Choe, Wade Rush, Alexei Kanareykin, Xuewen Fu, and Yimei Zhu, Review of Scientific Instruments (2020). The article can be accessed at https://doi.org/10.1063/1.5131758 .