Seminars Archive

Ultrafast Electron Crystallography (UEC) gives insights on the electron phonon coupling in solids.

Abstract
The decay of electronic excitations, as well as optically excited structural phase transitions, can be directly observed by watching the motion of atoms in a solid with femtosecond time resolution. The reaction of the lattice to an electronic excitation reveals microscopic details on the scattering rate. Recent advances in UEC have made possible the observation of lattice motions with femtosecond resolution in time and fractions of a picometer in space. High energy electrons have a cross section for the interaction with matter 106 times higher then x-rays. They are sensitive to light elements and can be generated in a table top set-up. In the Reflection High Energy Electron Diffraction (RHEED) geometry, one can tune the bulk sensitivity by changing the angle of incidence of the electron beam. This is ideal for the study of ultrathin materials such as graphene, multilayers and nano-patterned sample, and also biological aggregates or single crystals. In this seminar, I will review some recent results obtained by means of UEC on different systems, such as nanopatterned cuprates superconductors, thin films of ferroelectric PbTiO3, single crystal graphite, and the interface between SiC and graphene which forms a Schottky barrier of great interest for applications in electronic devices. A brief overview of the future developments of the technique will be discussed; in particular, attention will be focused on the improvement of time-resolution and the possibility to detect inelastic processes, combining UEC with Electron Energy Loss Spectroscopy (EELS).