Sample preparation methods for femtosecond electron diffraction experiments

Exploring the dynamics of Charge density wave system 1T-TaS2 via femtosecond electron diffraction demonstrated the power of this technique for studying ultrafast structural phenomena in strongly correlated electron materials [1]. The results revealed first direct information on the order parameter dynamics of Charge Density Waves as well as on their photo-induced phase transition. A prerequisite to perform such experiments on modern quantum materials is the availability of laterally large (∼100 μm) and sufficiently thin (<100 nm) single crystalline samples. Different approaches to reach these specifications have been tried out and their effect on sample integrity has been investigated. Finally, using an ultra-microtome, we were able to prepare 30 nm free standing single crystalline films of 1T-TaS2 with lateral dimensions of 200 μm×200 μm. We have characterized these films with different techniques for their stoichiometric and crystalline integrity, ensuring no measurable alternation of sample properties. The application of this sample thinning technique is expected to find its use in further structural dynamics studies, as well as in optical time-resolved studies where homogeneous excitation profile and/or data in transmission geometry may be required.

► Femtosecond electron diffraction (FED) is a novel structural dynamics technique. ► FED requires free standing single crystalline films of sub 100 nm thickness. ► Various thinning methods have been used and the resulting film integrity compared. ► With ultra-microtome large free-standing 30 nm single crystal films are prepared.