Raman spectra of graphene exfoliated on insulating crystalline substrates

Bukowska, Hanna; Meinerzhagen, F.; Akcöltekin, S.; Ochedowski, Oliver; Neubert, Michael; Buck, V.; Schleberger, Marika

doi:10.1088/1367-2630/13/6/063018

Cited by 23 publications

(25 citation statements)

References 38 publications

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“…To obtain correct height measurements, KPFM [23–24] imaging is performed simultaneously by applying an AC voltage of 1 V amplitude at a frequency of 1.2 kHz added to the DC bias regulated to minimize electrostatic forces. To remove volatile surface contaminants that can significantly influence LCPD measurements [25], the sample is heated in UHV to 500 K prior to measurements. All images in this paper are presented without filtering or smoothing.…”

Section: Methodsmentioning

confidence: 99%

Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

Temmen¹,

Ochedowski²,

Bußmann³

et al. 2013

Beilstein J. Nanotechnol.

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SummaryTwisted few layer graphene (FLG) is highly attractive from an application point of view, due to its extraordinary electronic properties. In order to study its properties, we demonstrate and discuss three different routes to in situ create and identify (twisted) FLG. Single layer graphene (SLG) sheets mechanically exfoliated under ambient conditions on 6H-SiC(0001) are modified by (i) swift heavy ion (SHI) irradiation, (ii) by a force microscope tip and (iii) by severe heating. The resulting surface topography and the surface potential are investigated with non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM). SHI irradiation results in rupture of the SLG sheets, thereby creating foldings and bilayer graphene (BLG). Applying the other modification methods creates enlarged (twisted) graphene foldings that show rupture along preferential edges of zigzag and armchair type. Peeling at a folding over an edge different from a low index crystallographic direction can result in twisted BLG, showing a similar height as Bernal (or AA-stacked) BLG in NC-AFM images. The rotational stacking can be identified by a significant contrast in the local contact potential difference (LCPD) measured by KPFM.

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Section: Methodsmentioning

confidence: 99%

Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

Temmen¹,

Ochedowski²,

Bußmann³

et al. 2013

Beilstein J. Nanotechnol.

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“…9 For graphene it is well known that the charge carrier concentration can be influenced by the substrate. 25,26 The observed changes in the photoluminescence of freestanding single-layer MoS 2 can thus be understood when assuming n-type doping of the MoS 2 by charge transfer effects from the substrate. Therefore, the emission of the exciton (A) is suppressed on the substrate; instead, the observed photoluminescence of single-layer MoS 2 on Si/SiO 2 substrate is primarily from the trion (A − ).…”

Section: A Freestanding Few-layer Mos2mentioning

confidence: 99%

Photoluminescence of freestanding single- and few-layerMoS2

et al. 2014

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We present a photoluminescence study of freestanding and Si/SiO2 supported single-and few-layer MoS2. The single-layer exciton peak (A) is only observed in freestanding MoS2. The photoluminescence of supported single-layer MoS2 is instead originating from the A − (trion) peak as the MoS2 is n-type doped from the substrate. In bilayer MoS2, the van der Waals interaction with the substrate is decreasing the indirect band gap energy by up to ≈ 80 meV. Furthermore, the photoluminescence spectra of suspended MoS2 can be influenced by interference effects.

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“…Each working 35 electrode had the same area of 20 mm × 20 mm with the weight of total active materials about 2.9 mg (2.45 mg NCH and 0.45 mg graphene). Raman spectroscopy was recorded on a DXR Raman 20 Microscope with an excitation length of 532 nm.…”

Section: Characterizationmentioning

confidence: 99%

“…At the same time, efficient energy storage devices with high energy and power densities are urgently 35 demanded. have been exploited quickly.…”

Section: Introductionmentioning

confidence: 99%

“…The G band (~1590 cm -1 ) is attributed to the vibration 15 of sp 2 -bonded carbon atoms, while D band (~1350 cm -1 ) arises from the disorders or defects and 2D band at ~2700 cm -1 is originated from a double-resonance process. 35 Moreover, the integrated intensity ratio between the G and 2D bands (I G /I 2D ) reveals that the graphene is with few layers. 3, only G and 2D bands can be observed in G/NF and NCH/G/NF electrodes, which confirms the high structural 20 quality of defect-free graphene.…”

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Controllable synthesis of 3D binary nickel–cobalt hydroxide/graphene/nickel foam as a binder-free electrode for high-performance supercapacitors

et al. 2015

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10Binder-free electrodes based on 3D porous nickel cobalt binary hydroxides (NCH)/graphene (G) composites on nickel foam (NF) for supercapacitors are fabricated via chemical vapor deposition (CVD) process combined with electrochemical deposition (ED) method. High quality graphene grown on NF makes the surface more suitable for deposition 3D porous NCH and enhances the conductivity of electrode at the same time. The 3D structure can improve the electron transport 15 ability and make more active sites contact with electrolyte sufficiently. The morphology and electrochemical performance of NCH/G/NF electrodes can be readily manipulated by adjusting the deposition current density and the Ni/Co ratio of deposition solution. Attributed to the synergetic effect of the above factors, high capacitance with enhanced stability and rate capability is achieved. Specifically, at the deposition current density of 0.625 mA cm -2 and Ni/Co 20 ratio of 1:1, the NCH11/G/NF electrode exhibits maximum specific capacitance of 1410 F g -1 at 2 A g -1 . When the current density increases to 4 A g -1 , the capacitance is still 1328 F g -1 with high capacitance retention of 94.2 %. After 2500 cycles, the capacitance retention is 92.1 %, which is higher than that of common slurry-coating electrode. To research its practical application, an asymmetric supercapacitor with NCH11/G/NF electrode as positive electrode and activated 25 carbon as negative electrode was fabricated. The asymmetric device exhibits a prominent energy density of 33.75 Wh kg -1 at a power density of 750 W kg -1 . The binder-free electrode with superior performance has been proved to be very promising for energy storage. 65to the nearly identical physical and chemical properties and the miscible ions in aqueous solution of nickel and cobalt. 14 What's more, the binary system not only inherits the merits of their individual components, but also yields much higher electrochemical performance. The atom substitution will 70 increase electrical conductivity and effectively enhance the active-site density and roughness of the final binary product. 15,

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Raman spectra of graphene exfoliated on insulating crystalline substrates

Cited by 23 publications

References 38 publications

Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

Photoluminescence of freestanding single- and few-layerMoS2

Controllable synthesis of 3D binary nickel–cobalt hydroxide/graphene/nickel foam as a binder-free electrode for high-performance supercapacitors

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