Browsing by Author "Meyer, Jannik C."

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    Atomic-Scale Deformations at the Interface of a Mixed-Dimensional van der Waals Heterostructure
    (AMERICAN CHEMICAL SOCIETY, 2018-07-17) Mustonen, Kimmo Aleksi; Hussain, Aqeel; Hofer, Christoph; Reza Ahmadpour Monazam, Mohammad; Mirzayev, Rasim; Elibol, Kenan; Laiho, Patrik; Mangler, Clemens; Jiang, Hua; Susi, Toma; Kauppinen, Esko I.; Kotakoski, Jani; Meyer, Jannik C.; Department of Applied Physics; NanoMaterials; University of Vienna
    Molecular self-assembly due to chemical interactions is the basis of bottom-up nanofabrication, whereas weaker intermolecular forces dominate on the scale of macromolecules. Recent advances in synthesis and characterization have brought increasing attention to two- and mixed-dimensional heterostructures and it has been recognized that van der Waals (vdW) forces within the structure may have a significant impact on their morphology. Here, we suspend single-walled carbon nanotubes (SWCNTs) on graphene to create a model system for the study of a 1D-2D molecular interface through atomic resolution scanning transmission electron microscopy observations. When brought in contact, we observe radial deformation of SWCNTs and the emergence of long-range linear grooves in graphene revealed by three-dimensional reconstruction of the heterostructure. These topographic features are strain-correlated but show no sensitivity to carbon nanotube helicity, electronic structure, or stacking order. Finally, despite random deposition of the nanotubes, we show that the competition between strain and vdW forces results in aligned carbon-carbon interfaces spanning hundreds of nanometers.
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    Vibrational Properties of a Two-Dimensional Silica Kagome Lattice
    (2016-12-27) Björkman, Torbjörn; Skakalova, Viera; Kurasch, Simon; Kaiser, Ute; Meyer, Jannik C.; Smet, Jurgen H.; Krasheninnikov, Arkady V.; Department of Applied Physics; Slovak University of Technology; Ulm University; University of Vienna; Max Planck Institute for Solid State Research
    Kagome lattices are structures possessing fascinating magnetic and vibrational properties, but in spite of a large body of theoretical work, experimental realizations and investigations of their dynamics are scarce. Using a combination of Raman spectroscopy and density functional theory calculations, we study the vibrational properties of two-dimensional silica (2D-SiO2), which has a kagome lattice structure. We identify the signatures of crystalline and amorphous 2D-SiO2 structures in Raman spectra and show that, at finite temperatures, the stability of 2D-SiO2 lattice is strongly influenced by phonon-phonon interaction. Our results not only provide insights into the vibrational properties of 2D-SiO2 and kagome lattices in general but also suggest a quick nondestructive method to detect 2D-SiO2.