Berlin 2018 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 58: Liquid and Amorphous Metals
MM 58.6: Talk
Thursday, March 15, 2018, 13:00–13:15, TC 010
In-situ observation of electron beam induced nanocrystallization of an ultra thin W foil — •Stefan Noisternig1, Clemens Mangler1, Christian Ebner1, Christian Rentenberger1, Hans-Peter Karnthaler1, and Willem Tichelaar2 — 1University of Vienna, Physics of Nanostructured Materials, 1090 Vienna, Austria — 2CEOS-GmbH, 69126 Heidelberg, Germany
An amorphous 2nm thin tungsten (W) foil supported by 3 nm carbon on a QUANTIFOIL grid is studied in an UltraSTEM 100 Nion dedicated scanning transmission electron microscope (STEM).
During the observation in the STEM the amorphous structure of W converts to a partially nanocrystalline one. The time to form the crystalline structure depends on the radiation dose of the electron beam. A Fast Fourier Transformation analysis of High Angle Annular Dark Field (HAADF) images reveals that WC0.82 and W3C0.375 nanocrystals formed during the radiation of the amorphous W foil under the electron beam.
During the continuous acquisitions a movement of bright dots is observed in HAADF images. We interpret this phenomenon as an observed surface diffusion of W atoms which is here activated well below the knock-on energy (above 1 MeV) for W. Mean square displacements of bright dots are measured at amorphous areas and at crystalline areas. The calculated diffusion parameters are then compared to literature values obtained with different methods.
We kindly acknowledge financial support by the Austrian Science Fund (FWF): [I1309].