OIST Seminar by Dr. Jinfeng Yang "MeV Electron Diffraction and Microscopy"

Dr. Jinfeng Yang from The Institute of Scientific and Industrial Research, Osaka University

 

Abstract:

The direct visualization of structural dynamic processes in matter occurring on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions has long been a goal in science. Transmission electron microscopy (TEM) is a powerful tool to observe directly the image from specimen with high spatial resolution. When coupled with time resolution, it, which called ultrafast electron microscopy (UEM), would be the strongest tool for the study of ultrafast dynamics in materials. Currently, the UEM with the time-spatial resolution of 10 ns and 10 nm has been achieved in conventional TEM through the use of photo-activated electron source driven by a nanosecond laser in the non-space-charge-limited regime with ns-long pulse length. A large number of important phenomena, i.e. phase transformations, melting, resolidification, nucleation and growth of damage in nanosecond time region, have been investigated. For the high time resolution development, a multi-shot (or stroboscopic) UEM, where as few as one electron in a pulse being sufficient for a ~100 MHz repetition rate laser system, has been proposed. However, to accumulate more signals, one need merely cycle the experiment for a longer time, within the limits of the stability of the microscope and the sample.