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Author: Hübner, Uwe × End date: 2022 × Start date: 2020 × End date: 2019 × Start date: 2010 × DDC: 530 ×

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Now showing 1 - 3 of 3
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    Controlled growth of transition metal dichalcogenide monolayers using Knudsen-type effusion cells for the precursors
    (Bristol : IOP Publishing, 2019) George, Antony; Neumann, Christof; Kaiser, David; Mupparapu, Rajeshkumar; Lehnert, Tibor; Hübner, Uwe; Tang, Zian; Winter, Andreas; Kaiser, Ute; Staude, Isabelle; Turchanin, Andrey
    Controlling the flow rate of precursors is essential for the growth of high quality monolayer single crystals of transition metal dichalcogenides (TMDs) by chemical vapor deposition. Thus, introduction of an excess amount of the precursors affects reproducibility of the growth process and results in the formation of TMD multilayers and other unwanted deposits. Here we present a simple method for controlling the precursor flow rates using the Knudsen-type effusion cells. This method results in a highly reproducible growth of large area and high density TMD monolayers. The size of the grown crystals can be adjusted between 10 and 200 μm. We characterized the grown MoS2 and WS2 monolayers by optical, atomic force and transmission electron microscopies as well as by x-ray photoelectron, Raman and photoluminescence spectroscopies, and by electrical transport measurements showing their high optical and electronic quality based on the single crystalline nature.
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    Laboratory setup for extreme ultraviolet coherence tomography driven by a high-harmonic source
    (Melville, NY : American Inst. of Physics, 2019) Nathanael, Jan; Wünsche, Martin; Fuchs, Silvio; Weber, Thomas; Abel, Johann J.; Reinhard, Julius; Wiesner, Felix; Hübner, Uwe; Skruszewicz, Slawomir J.; Paulus, Gerhard G.; Rödel, Christian
    We present a laboratory beamline dedicated to nanoscale subsurface imaging using extreme ultraviolet coherence tomography (XCT). In this setup, broad-bandwidth extreme ultraviolet (XUV) radiation is generated by a laser-driven high-harmonic source. The beamline is able to handle a spectral range of 30-130 eV and a beam divergence of 10 mrad (full width at half maximum). The XUV radiation is focused on the sample under investigation, and the broadband reflectivity is measured using an XUV spectrometer. For the given spectral window, the XCT beamline is particularly suited to investigate silicon-based nanostructured samples. Cross-sectional imaging of layered nanometer-scale samples can be routinely performed using the laboratory-scale XCT beamline. A depth resolution of 16 nm has been achieved using the spectral range of 36-98 eV which represents a 33% increase in resolution due to the broader spectral range compared to previous work. © 2019 Author(s).
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    A high resolution extreme ultraviolet spectrometer system optimized for harmonic spectroscopy and XUV beam analysis
    (Melville, NY : American Inst. of Physics, 2019) Wünsche, Martin; Fuchs, Silvio; Weber, Thomas; Nathanael, Jan; Abel, Johann J.; Reinhard, Julius; Wiesner, Felix; Hübner, Uwe; Skruszewicz, Slawomir J.; Paulus, Gerhard G.; Rödel, Christian
    We present a modular extreme ultraviolet (XUV) spectrometer system optimized for a broad spectral range of 12-41 nm (30-99 eV) with a high spectral resolution of λ/Δλ 784 ± 89. The spectrometer system has several operation modes for (1) XUV beam inspection, (2) angular spectral analysis, and (3) imaging spectroscopy. These options allow for a versatile use in high harmonic spectroscopy and XUV beam analysis. The high performance of the spectrometer is demonstrated using a novel cross-sectional imaging method called XUV coherence tomography. © 2019 Author(s).