First time resolved Pilot Experiment by SwissFEL: Semiconductor to metal transition in Ti₃O₅ nanocrystals

On the 30th of November 2017 SwissFEL saw its first time resolved pilot experiment in the Bernina experimental station of the SwissFEL ARAMIS beamline. A team of scientists from the University of Rennes, ESRF and PSI, led by Marco Cammarata (Univ. Rennes) and Henrik Lemke (PSI), successfully started the experimental phase at SwissFEL. The goal was to study the picosecond dynamics of a light-induced phase transition from a semiconductor to metallic crystal structure in a Titanium Oxide (D). In nanoparticles, the transition occurs reversibly and may be interesting for data storage applications. The transition was studied by powder X-ray diffraction using the 3rd Harmonic 6.6 KeV Photons (~1% of fundamental @ 2.2 KeV 220 μJ) of SwissFEL (A: Diffraction image, 100 pulse average ). After excitation with infrared laser light (800nm, 42 mJ/cm2), changes in the Debye-Scherrer diffraction rings indicate the transient population changes in the different phases (B). A cascade of dynamic processes from few picosecond acoustic lattice deformation to phase transition from ~10 picosecond to microsecond timescale could be observed (B/C). Once fully analyzed the scientists hope to fully describe the time scale and mechanisms of the photo transformation read more.