Skip over navigation

 

Principles of Ultrafast Transmission Electron Microscopy with Applications in Materials Science

David Flannigan (University of Minnesota)

Mechanics of Phase Transforming and Multifunctional Materials

Tue 4:20 - 5:40

CIT 219

The previous century was filled with great advances in static structure determination and atomic-scale visualization of materials through X-ray and electron-based techniques. While undeniably powerful, knowing the structure tells only part of the story. What is missing is the direct visualization of how all components of the system behave when driven far from equilibrium. With ultrafast transmission electron microscopy (UTEM), one is able to extend the millisecond temporal capabilities typical of standard transmission electron microscopes (TEMs) into the femtosecond domain. This is accomplished by interfacing an appropriately-modified electron microscope with short-pulsed lasers. By doing so, the temporal resolution is no longer dictated by CCD camera read-out rates. Instead, resolution is directly tied to the laser pulse properties used to generate photoelectron packets in the TEM gun region. In this way, one may directly obtain structural and electronic information for transient states via time-resolved imaging, diffraction, and spectroscopy. In this talk, I will show how UTEM has been used to directly visualize a variety of phenomena. Specifically, I will discuss: (1) visualization of nanosecond adhesion and frictional processes and MHz oscillatory motions of single metal-organic crystals on the nanometer spatial scale, (2) single-shot UTEM imaging of sub-microsecond crystal photodecomposition and subsequent metal nanoparticle formation via sintering, (3) picosecond atomic to nanoscale structural dynamics and photoactuation of carbon nanotubes and nanotube bundles with sub-picometer sensitivity, and (4) direct visualization of nanostructure evanescent fields via coupling of relativistic electrons with photons on the femtosecond time-scale. The talk will illustrate the unique capabilities and extraordinary breadth of studies that can be done with UTEM while emphasizing the exciting possibilities for fundamental discoveries.