Chong-Yu Ruan, Michigan State University
In situ imaging of complex phase transitions in functional transition metal compounds at ultrafast timescales
Written by Trevor Clark
In high speed imaging only a small amount of the light/electron information can be captured. A high intensity brightness is required to be able to distinguish what is in the image. This is easy enough to do for light imaging by just adding more photons; however, it is not as simple for electrons: if packed into high densities their charges repel each other resulting in greatly reduced spatial resolution. This space-charge effect can be corrected by radio frequency (RF) longitudinal lenses, and allows for the capability of imaging extremely fast processes. These RF cavities allow for correction of temporal and spatial anomalies by changing the high-volume electron flow from turbulent to laminar. This retains benefits of increased brightness from increased dose, while limiting the negative resolution impacts from the space-charge effect. This lens setup has been used to study the ultrafast phase transitions in transition metal dichalcogenide systems, and is a promising tool for advanced materials characterization at the ultrafast time scale.