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Author: Bousa, Milan × Author: Hübner, Uwe × End date: 2019 × Start date: 2010 × Type: Text × WGL Institute: IPHT ×

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    Mastering the Wrinkling of Self-supported Graphene
    (Berlin : Nature Pulishing, 2017) Pacakova, Barbara; Verhagen, Timotheus; Bousa, Milan; Hübner, Uwe; Vejpravova, Jana; Kalbac, Martin; Frank, Otakar
    We present an approach that allows for the preparation of well-defined large arrays of graphene wrinkles with predictable geometry. Chemical vapor deposition grown graphene transferred onto hexagonal pillar arrays of SiO2 with sufficiently small interpillar distance forms a complex network of two main types of wrinkle arrangements. The first type is composed of arrays of aligned equidistantly separated parallel wrinkles propagating over large distances, and originates from line interfaces in the graphene, such as thin, long wrinkles and graphene grain boundaries. The second type of wrinkle arrangement is composed of non-aligned short wrinkles, formed in areas without line interfaces. Besides the presented hybrid graphene topography with distinct wrinkle geometries induced by the pre-patterned substrate, the graphene layers are suspended and self-supporting, exhibiting large surface area and negligible doping effects from the substrate. All these properties make this wrinkled graphene a promising candidate for a material with enhanced chemical reactivity useful in nanoelectronic applications.
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    Superlattice in collapsed graphene wrinkles
    (Berlin : Nature Publishing, 2019) Verhagen, Timotheus; Pacakova, Barbara; Bousa, Milan; Hübner, Uwe; Kalbac, Martin; Vejpravova, Jana; Frank, Otakar
    Topographic corrugations, such as wrinkles, are known to introduce diverse physical phenomena that can significantly modify the electrical, optical and chemical properties of two-dimensional materials. This range of assets can be expanded even further when the crystal lattices of the walls of the wrinkle are aligned and form a superlattice, thereby creating a high aspect ratio analogue of a twisted bilayer or multilayer – the so-called twisted wrinkle. Here we present an experimental proof that such twisted wrinkles exist in graphene monolayers on the scale of several micrometres. Combining atomic force microscopy and Raman spectral mapping using a wide range of visible excitation energies, we show that the wrinkles are extremely narrow and their Raman spectra exhibit all the characteristic features of twisted bilayer or multilayer graphene. In light of a recent breakthrough – the superconductivity of a magic-angle graphene bilayer, the collapsed wrinkles represent naturally occurring systems with tuneable collective regimes.