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O: Fachverband Oberflächenphysik

O 52: Poster Session - New Methods: Experiments

O 52.7: Poster

Dienstag, 17. März 2020, 18:15–20:00, P2/1OG

Femtosecond point-projection microscopy and holography – electron source coherence and spatial resolution — Faruk Krečinić and •Ralph Ernstorfer — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

Femtosecond point-projection microscopy (fs-PPM) is a technique for visualizing ultrafast charge motion in real space. A nanotip electron source is brought close to the sample such that the diverging electron beam projects a magnified image of the sample onto the detector. Due to the use of low-energy electrons, the PPM image is highly sensitive to local (nanoscale) electric fields. At high magnification, one observes an in-line holographic projection of the sample that is sensitive enough to visualize a single elementary charge [1]. By triggering the emission of electrons from the nanotip with an ultrafast laser it is possible to perform pump-probe PPM, visualizing the ultrafast dynamics of charge carriers with nanometer resolution [2,3]. However, the photoemission process can also lead to a decrease in the spatial resolution. Using a semi-classical model we show how spatial and temporal coherence, as well as electron-optical aberrations and the apex geometry, affect the spatial resolution of the PPM technique. The introduced semi-classical model is in principle more generally applicable to investigations of the wave-optical properties of (photo)electron sources for electron microscopy.

[1] T. Latychevskaia, et al., Nano Letters, 16(9), 5469-5474, (2016). [2] M. Müller, et al., Nat. Comm., 5, 5292 (2014). [3] F. Krečinić, et al., arXiv:1803.01766, (2018).