Development of ultrafast four-dimensional precession electron diffraction

TL;DR

This paper introduces a 4D precession electron diffraction system that enables quantitative analysis of ultrafast crystal structure dynamics by capturing time and incident-angle dependent diffraction patterns, overcoming previous limitations.

Contribution

The development of a 4D-PED system that records time and incident-angle dependent diffraction patterns for quantitative ultrafast crystal structure analysis.

Findings

Quantitative determination of ultrafast crystal structure changes in VTe₂.

Ability to estimate reciprocal lattice vector changes from diffraction data.

Demonstration of 4D-PED's capability for ultrafast structural dynamics investigation.

Abstract

Ultrafast electron diffraction/microscopy technique enables us to investigate the nonequilibrium dynamics of crystal structures in the femtosecond-nanosecond time domain. However, the electron diffraction intensities are in general extremely sensitive to the excitation errors (i.e., deviation from the Bragg condition) and the dynamical effects, which had prevented us from quantitatively discussing the crystal structure dynamics. Here, we develop a four-dimensional precession electron diffraction (4D-PED) system by which time ($t$) and electron-incident-angle ($\phi$) dependences of electron diffraction patterns ($q_x,q_y$) are recorded. Nonequilibrium crystal structure refinement on VTe$_{2}$ demonstrates that the ultrafast change in the crystal structure can be quantitatively determined from 4D-PED. We further perform the analysis of the $\phi$ dependence, from which we can qualitatively estimate the change in the reciprocal lattice vector parallel to the optical axis. These results show the capability of the 4D-PED method for the quantitative investigation of ultrafast crystal structural dynamics.