Participants : G. M. Caruso (PhD)
This project involves two research groups of CEMES (I3EM and NeO) and is a collaboration between CEMES and LPS-Orsay (Mathieu Kociak).
The FemTOTEM project aims at developing an Ultrafast Transmission Electron Microscope (UTEM) based on a high brightness laser-driven cold field emission electron source. This will be achieved by bringing together a femtosecond laser source and a customized field emission Transmission Electron Microscope (FE-TEM). This combination of femtosecond time resolution, high brightness (allowing high spatial resolution and coherence of electrons) and energy resolution will have a unique potential for frontier research in nanophysics and materials science.
The first part of this project involves instrumental developments. First, we will demonstrate and characterize laser driven field emission from the customized electron source of a commercial 200kV TEM. The femtosecond cold field emission gun that we have already mounted in a dedicated Ultra High Vacuum (UHV) bench will be completely characterized in terms of brightness, emittance and energy spectrum as a function of laser parameters and extraction voltage. Then, it will be transferred on a TEM column. Its potential for electron microscopy experiments will be thoroughly investigated first on routine TEM applications and later on more demanding experiments. A system allowing light injection and collection on the TEM sample, already installed, will allow us to perform original experiments involving electrons and photons. The principle of an ultrafast TEM is show on the Figure 1. An ultrashort laser pulse excites the sample inserted inside the objective lens. A second laser pulse, delayed, will trigger the emission of ultrashort electron pulses used to probe the sample.
Experimental means used
Service TEM, Spectroscopie optique et préparation du CEMES. Centre de Calcul CALMIP.
The FemtoTEM project is supported by Institut de Physique of CNRS, Agence Nationale de la Recherche (grant ANR-14-CE26-0013) and NEXT collaborative project MUSE.