Filters

2017 - 20192

More filters

2021 - 20232
Reset filters

Settings

Author: Wolf, Daniel × DDC: 600 ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Chromium Trihalides CrX3 (X = Cl, Br, I): Direct Deposition of Micro- and Nanosheets on Substrates by Chemical Vapor Transport
    (Weinheim : Wiley-VCH, 2019) Grönke, Martin; Buschbeck, Benjamin; Schmidt, Peer; Valldor, Martin; Oswald, Steffen; Hao, Qi; Lubk, Axel; Wolf, Daniel; Steiner, Udo; Büchner, Bernd; Hampel, Silke
    The experimental observation of intrinsic ferromagnetism in single layered chromium trihalides CrX3 (X = Cl, Br, I) has gained outstanding attention recently due to their possible implementation in spintronic devices. However, the reproducible preparation of highly crystalline chromium(III) halide nanolayers without stacking faults is still an experimental challenge. As chromium trihalides consist of adjacent layers with weak interlayer coupling, the preparation of ultrathin CrX3 nanosheets directly on substrates via vapor transport proves as an advantageous synthesis technique. It is demonstrated that vapor growth of ultrathin highly crystalline CrX3 micro- and nanosheets succeeds directly on yttrium stabilized zirconia substrates in a one-step process via chemical vapor transport (CVT) in temperature gradients of 100 K (600 °C → 500 °C for CrCl3 and 650 °C → 550 °C for CrBr3 or CrI3) without a need for subsequent delamination. Due to simulation results, optimization of synthesis conditions is realized and phase pure CrX3 nanosheets with thicknesses ≤25 nm are obtained via short term CVT. The nanosheets morphology, crystallinity, and phase purity are analyzed by several techniques, including microscopy, diffraction, and spectroscopy. Furthermore, a potential subsequent delamination technique is demonstrated to give fast access to CrX3 monolayers using the example of CrCl3. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Thumbnail Image
    Item
    Nanorattles with tailored electric field enhancement
    (Cambridge : RSC Publ., 2017) Schnepf, Max J.; Mayer, Martin; Kuttner, Christian; Tebbe, Moritz; Wolf, Daniel; Dulle, Martin; Altantzis, Thomas; Formanek, Petr; Förster, Stephan; Bals, Sara; König, Tobias A. F.; Fery, Andreas
    Nanorattles are metallic core-shell particles with core and shell separated by a dielectric spacer. These nanorattles have been identified as a promising class of nanoparticles, due to their extraordinary high electric-field enhancement inside the cavity. Limiting factors are reproducibility and loss of axial symmetry owing to the movable metal core; movement of the core results in fluctuation of the nanocavity dimensions and commensurate variations in enhancement factor. We present a novel synthetic approach for the robust fixation of the central gold rod within a well-defined box, which results in an axisymmetric nanorattle. We determine the structure of the resulting axisymmetric nanorattles by advanced transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Optical absorption and scattering cross-sections obtained from UV-vis-NIR spectroscopy quantitatively agree with finite-difference time-domain (FDTD) simulations based on the structural model derived from SAXS. The predictions of high and homogenous field enhancement are evidenced by scanning TEM electron energy loss spectroscopy (STEM-EELS) measurement on single-particle level. Thus, comprehensive understanding of structural and optical properties is achieved for this class of nanoparticles, paving the way for photonic applications where a defined and robust unit cell is crucial.