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Author: Erbe, Artur × DDC: 530 ×

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    Autocorrected off-axis holography of two-dimensional materials
    (College Park, ML : American Physical Society, 2020) Kern, Felix; Linck, Martin; Wolf, Daniel; Alem, Nasim; Arora, Himani; Gemming, Sibylle; Erbe, Artur; Zettl, Alex; Büchner, Bernd; Lubk, Axel
    The reduced dimensionality in two-dimensional materials leads to a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high-resolution microscopy techniques are indispensable. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the two-dimensional material. We demonstrate these features with the example of h-BN, for which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges.
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    Observation of Ultrafast Solid-Density Plasma Dynamics Using Femtosecond X-Ray Pulses from a Free-Electron Laser
    (College Park, Md. : APS, 2018) Kluge, Thomas; Rödel, Melanie; Metzkes-Ng, Josefine; Pelka, Alexander; Laso Garcia, Alejandro; Prencipe, Irene; Rehwald, Martin; Nakatsutsumi, Motoaki; McBride, Emma E.; Schönherr, Tommy; Garten, Marco; Hartley, Nicholas J.; Zacharias, Malte; Grenzer, Jörg; Erbe, Artur; Georgiev, Yordan M.; Galtier, Eric; Nam, Inhyuk; Lee, Hae Ja; Glenzer, Siegfried; Bussmann, Michael; Gutt, Christian; Zeil, Karl; Rödel, Christian; Hübner, Uwe; Schramm, Ulrich; Cowan, Thomas E.
    The complex physics of the interaction between short-pulse ultrahigh-intensity lasers and solids is so far difficult to access experimentally, and the development of compact laser-based next-generation secondary radiation sources, e.g., for tumor therapy, laboratory astrophysics, and fusion, is hindered by the lack of diagnostic capabilities to probe the complex electron dynamics and competing instabilities. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that small-angle x-ray scattering of femtosecond x-ray free-electron laser pulses facilitates new capabilities for direct in situ characterization of intense short-pulse laser-plasma interactions at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short-pulse high-intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the preinscribed grating, due to plasma expansion. The density maxima are interleaved, forming a double frequency grating in x-ray free-electron laser projection for a short time, which is a hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets.