Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 84: Focus Session: Structural Dynamics in Nanoscale Materials Probed by Ultrashort Electron Pulses

O 84.7: Vortrag

Donnerstag, 19. März 2015, 17:00–17:15, MA 005

Developments in ultrafast electron microscopy and diffraction — Alexander Bainbridge and •William Bryan — Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, UK

A progress report on recent ultrafast electron microscopy and diffraction studies at Swansea University (UK) will be presented. Facilities to time-resolve charge migration on nanometre to micron scales are to be discussed, and are currently propagating sub-100fs electron pulses from a nanoscale metal tip (NSMT) to thin solid state samples mounted on a TEM substrate. This work employs the 20fs 2uJ output from a Light Conversion Orpheus-N OPA, which is split into a pump pulse illuminating the target and probe driving electron emission from the NSMT. Laser delivery includes an external compressor, FROG and pointing stabilisation. Field emission from this system indicates imaging to sub-hundred nm is currently possible.

Recent simulations investigating the ultimate time resolution of our PPM instrument will also be presented, and we will discuss balancing the requirements for field of view over time resolution. Modelling of electron pulse collimation with an electrostatic microlens will be presented, which will facilitate coherent diffractive imaging with time resolution, opening the door to tracking charge motions on the atomic scale. Clearly instrument design and implementation is just the start, and to illustrate our broad interests in this field, research directions involving graphene liquid cells, coupling nanorods to 2D crystalline materials and tracking charge flow through plasmonic nanoparticle strings will be discussed.