Streak-camera reflection high-energy electron diffraction for dynamics of surface crystallography

A new technique for ultrafast dynamics of surface crystallography was developed by combining reflection high-energy electron diffraction with the electron deflectors of a streak camera system. A one-dimensional distribution of electrons scattered by a crystal surface is selected by a linear slit on a screen, and then the electrons are quickly deflected by the sweep electrodes behind the slit. Thus, a temporal evolution of the one-dimensional diffraction pattern can be displayed as a streak image on a screen. This is a unique method of time-resolved electron diffraction, as a pulsed electron beam is not required to obtain a temporal evolution. The temporal evolution of the diffraction pattern can be projected on a screen from single-shot measurements. The technique was tested on an Si(111)-7 × 7 surface, and the dynamics of the surface structure were successively obtained from changes in spot intensities. Although the present time time-resolution was limited by the present pumping laser ~ 5 ns, the nominal resolution of the streak system is expected to be ~100 ps.