4D Nanoscale Diffraction Observed by Convergent-Beam Ultrafast Electron Microscopy
Aycan Yurtsever and
Ahmed H. Zewail*
Diffraction with focused electron probes is among the most powerful
tools for the study of time-averaged nanoscale structures in
condensed matter. Here, we report four-dimensional (4D) nanoscale
diffraction, probing specific site dynamics with 10 orders of
magnitude improvement in time resolution, in convergent-beam
ultrafast electron microscopy (CB-UEM). As an application, we
measured the change of diffraction intensities in laser-heated
crystalline silicon as a function of time and fluence. The structural
dynamics (change in 7.3 ± 3.5 picoseconds), the temperatures
(up to 366 kelvin), and the amplitudes of atomic vibrations
(up to 0.084 angstroms) are determined for atoms strictly localized
within the confined probe area (10 to 300 nanometers in diameter).
We anticipate a broad range of applications for CB-UEM and its
variants, especially in the studies of single particles and
heterogeneous structures.
* To whom correspondence should be addressed. E-mail: zewail{at}caltech.edu
