Observation of large multiple scattering effects in ultrafast electron diffraction on single crystal silicon

TL;DR

This study reveals that multiple scattering effects significantly influence ultrafast electron diffraction measurements on single crystal silicon, challenging traditional interpretations and enabling new insights into non-equilibrium crystal dynamics.

Contribution

It demonstrates the importance of dynamical diffraction theory in analyzing ultrafast electron diffraction data and highlights the role of multiple scattering in Bragg peak dynamics.

Findings

Lattice heating can increase Bragg peak intensities contrary to Debye-Waller predictions.

Multiple scattering effects dominate the ultrafast Bragg peak response.

Considering multiple scattering enables quantitative analysis of defect dynamics.

Abstract

We report on ultrafast electron diffraction on high quality single crystal silicon. The ultrafast dynamics of the Bragg peaks exhibits a giant photo-induced response which can only be explained in the framework of dynamical diffraction theory, taking into account multiple scattering of the probing electrons in the sample. In particular, we show that lattice heating following photo-excitation can cause an unexpected increase of the Bragg peak intensities, in contradiction with the well-known Debye-Waller effect. We anticipate that multiple scattering should be systematically considered in ultrafast electron diffraction on high quality crystals as it dominates the Bragg peak dynamics. In addition, taking into account multiple scattering effects opens the way to quantitative studies of non-equilibrium dynamics of defects in quasi-perfect crystals.