Robust Graphene Membranes in a Silicon Carbide Frame

Waldmann, Daniel; Butz, Benjamin; Bauer, Sebastian; Englert, Jan M.; Jobst, Johannes; Ullmann, K.; Fromm, Felix; Ammon, Maximilian; Enzelberger, Michael; Hirsch, Andreas; Maier, Sabine; Schmuki, Patrik; Seyller, Thomas; Spiecker, Erdmann; Weber, Heiko B.

doi:10.1021/nn401037c

Cited by 17 publications

(17 citation statements)

References 39 publications

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“…The rhombus shaped lattice (Fig. 2c) is comparable with the rhombus lattice of AB Bernal graphite prevailing in the literature20212223242526, where each white dot of the AB rhombus shaped lattice is due to amplification from the two overlapped atoms of the AB bilayer graphene (Fig. 3b).…”

Section: Resultssupporting

confidence: 65%

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

Lee

Kim

Hembram

et al. 2016

Sci Rep

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Over the history of carbon, it is generally acknowledged that Bernal AB stacking of the sp2 carbon layers is the unique crystalline form of graphite. The universal graphite structure is synthesized at 2,600~3,000 °C and exhibits a micro-polycrystalline feature. In this paper, we provide evidence for a metastable form of graphite with an AA’ structure. The non-Bernal AA’ allotrope of graphite is synthesized by the thermal- and plasma-treatment of graphene nanopowders at ~1,500 °C. The formation of AA’ bilayer graphene nuclei facilitates the preferred texture growth and results in single-crystal AA’ graphite in the form of nanoribbons (1D) or microplates (2D) of a few nm in thickness. Kinetically controlled AA’ graphite exhibits unique nano- and single-crystalline feature and shows quasi-linear behavior near the K-point of the electronic band structure resulting in anomalous optical and acoustic phonon behavior.

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Section: Resultssupporting

confidence: 65%

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

Lee

Kim

Hembram

et al. 2016

Sci Rep

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“…The strong asymmetry in the emission pattern also explains the observed enhancement of the Raman intensity of free-standing EG [33,34] which was prepared by locally removing the SiC substrate. Shivaraman et al [33] and Waldmann et al [34] observed that the G band intensity is enhanced by a factor of approximately two and five compared to measurements of SiC supported regions, respectively. In the case of the free-standing regions, the index of refraction is the same on both sides of the graphene, leading to a symmetric intensity distribution.…”

Section: Enhanced Collection Efficiency Of the Top-down Geometrymentioning

confidence: 75%

Looking behind the scenes: Raman spectroscopy of top-gated epitaxial graphene through the substrate

et al. 2013

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Raman spectroscopy is frequently used to study the properties of epitaxial graphene grown on silicon carbide (SiC). In this work, we present a confocal micro-Raman study of epitaxial graphene on SiC(0001) in top-down geometry, i.e. in a geometry where both the primary laser light beam as well as the back-scattered light is guided through the SiC substrate. Compared to the conventional top-up configuration, in which confocal micro-Raman spectra are measured from the air side, we observe a significant intensity enhancement in top-down configuration, indicating that most of the Raman-scattered light is emitted into the SiC substrate. The intensity enhancement is explained in terms of dipole radiation at a dielectric surface. The new technique opens the possibility to probe graphene layers in devices where the graphene layer is covered by nontransparent materials. We demonstrate this by measuring gate-modulated Raman spectra of a top-gated epitaxial graphene field effect device. Moreover, we show that these measurements enable us to disentangle the effects of strain and charge on the positions of the prominent Raman lines in epitaxial graphene on SiC.

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“…In the given material, eBLG, dense dislocation networks have been observed recently by dark-field transmission electron microscopy (TEM; ref. 10) after removing the SiC substrate 25 . Figure 2a shows a superposition of three distinct dark-field TEM images exhibiting a real partial dislocation network, taken from ref.…”

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confidence: 99%

Linear magnetoresistance in mosaic-like bilayer graphene

et al. 2015

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The magnetoresistance of conductors usually has a quadratic dependence on magnetic field 1 , however, examples exist of non-saturating linear behaviour in diverse materials 2-6 . Assigning a specific microscopic mechanism to this unusual phenomenon is obscured by the co-occurrence and interplay of doping, mobility fluctuations and a polycrystalline structure 7,8 . Bilayer graphene has virtually no doping fluctuations, yet provides a built-in mosaic tiling due to the dense network of partial dislocations 9,10 . We present magnetotransport measurements of epitaxial bilayer graphene that exhibits a strong and reproducible linear magnetoresistance that persists to B = 62 T at and above room temperature, decorated by quantum interference effects at low temperatures. Partial dislocations thus have a profound impact on the transport properties in bilayer graphene, a system that is frequently assumed to be dislocation-free. It further provides a clear and tractable model system for studying the unusual properties of mosaic conductors.Although most real materials exhibit a quadratic magnetoresistance (MR), linear MR has been observed, even at room temperature, in conductors as varied as three-dimensional (3D) silver chalcogenides, semiconductors, topological insulators, and 2D multilayer graphenes 2-6,11-14 . Several theories have been developed seeking a general explanation of this phenomenon. A classical mechanism is suspected that mixes the transverse Hall resistance, which is linear in magnetic field, into the longitudinal resistance 1 . In particular, inhomogeneities may allow local Hall currents that in turn modify the potential landscape. The most rigorous model to treat this local Hall current map is that introduced by Parish and Littlewood (PL) in 2003, which represents the material as a mosaic of four-terminal interconnected conductive discs. This model has been invoked to explain linear MR in a number of experimental contexts. Nevertheless, an experiment which links the essence of this insightful but simple model to a real material is still lacking.To make a conceptually clear experiment in the spirit of PL it is first advantageous to treat a 2D system. Not only is magnetotransport an essentially 2D phenomenon, but also the mosaic nature may then in principle be entirely imaged. An essential requirement for a clear experimental realization of the PL model is a material for which the mosaic grains possess negligible internal structure-that is, a constant charge density, mobility and weak magnetoresistance. Furthermore, the granular structure and interconnect topology should be fully characterized. For such an experiment, bilayer epitaxial graphene is an ideal choice as it combines two-dimensionality with fixed charge density (due to the epitaxially defined substrate 15 ) and a room-temperature magnetoresistance expected to be weak 16 . Recently, we have discovered that epitaxial bilayer graphene, despite being a conductor with a good overall mobility, is threaded by a dense network of wellcharacterized partial d...

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Robust Graphene Membranes in a Silicon Carbide Frame

Cited by 17 publications

References 39 publications

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

The Nature of Metastable AA’ Graphite: Low Dimensional Nano- and Single-Crystalline Forms

Looking behind the scenes: Raman spectroscopy of top-gated epitaxial graphene through the substrate

Linear magnetoresistance in mosaic-like bilayer graphene

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