Scanning ultrafast electron microscopy
Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.
Additional Information© 2010 National Academy of Sciences. Contributed by Ahmed H. Zewail, June 29, 2010 (sent for review June 1, 2010). We thank Brett Barwick for the very helpful discussion and assistance during the design and operation of the microscope, especially in the initial stage. We also thank Lubomir Tuma, Michal Geryk, and Greg Schwind for exchange of information during the design stage of SUEM, and Tony Carpenter for all his effort in arranging for a timely installation in the laboratory. This work was supported by the Air Force Office of Scientific Research and the National Science Foundation in the Gordon and Betty Moore Center for physical biology at Caltech. Author contributions: D.-S.Y., O.F.M., and A.H.Z. performed research and wrote the paper. The authors declare no conflict of interest.
Published - Yang2010p11304P_Natl_Acad_Sci_Usa.pdf