Why Multilayer Graphene on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>4</mml:mn><mml:mi>H</mml:mi><mml:mtext mathvariant="normal">−</mml:mtext><mml:mi>SiC</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>000</mml:mn><mml:mover accent="true"><mml:mn>1</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mo stretchy="false">)</mml:mo></mml:math>Behaves Like a Single Sheet of Graphene

Hass, Joanna; Varchon, F.; Millán-Otoya, J. E.; Sprinkle, M.; Sharma, Nidhi; Heer, Walt A. de; Berger, Claire; First, Phillip N.; Magaud, Laurence; Conrad, E. H.

doi:10.1103/physrevlett.100.125504

Cited by 792 publications

(803 citation statements)

References 31 publications

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“…Rotationally faulted EG C exhibits very high carrier mobility due to reduced phonon scattering, which is consistent with this type of graphene layer-stacking. 17,23,23 We note that Hall crosses fabricated on EG C consist of both uniform (FWHM < 10% variation, Fig. 3b) and nonuniform (FWHM > 10% variation, Fig.…”

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confidence: 93%

“…Evidence suggests a mixture of graphene layers rotated by 30° or ±2° (R30 or R2 ± ) with respect to the SiC substrate exist (typically described as R30/R2 ± fault pairs). 23 Moreover, EG C with R30/R2 ± fault pairs contain significantly larger grains (>10x), 23 smaller 2D Raman peak widths (< 30 cm -1 compared to > 40 cm -1 ), and the absence of the defect-induced Raman peak (D-peak). 27,28 Based on these results, we identify multilayer EG C exhibiting a narrow 2D Raman peak and fit by a single Lorentzian (Fig.1d, top) as rotationally faulted epitaxial graphene (EG RF ).…”

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confidence: 99%

“…Equally important to layer thickness is layer-stacking, which can also be extracted from the 2D Raman spectra. 17,18,19,23 Multilayer EG C films can exhibit a 2D Raman peak characteristic of turbostratic graphite; 17 however, the layer-stacking may not be completely random. Evidence suggests a mixture of graphene layers rotated by 30° or ±2° (R30 or R2 ± ) with respect to the SiC substrate exist (typically described as R30/R2 ± fault pairs).…”

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confidence: 99%

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Correlating Raman Spectral Signatures with Carrier Mobility in Epitaxial Graphene: A Guide to Achieving High Mobility on the Wafer Scale

et al. 2009

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We report a direct correlation between carrier mobility and Raman topography of epitaxial graphene (EG) grown on silicon carbide (SiC). We show the Hall mobility of material on the Si-face of SiC [SiC(0001)] is not only highly dependent on thickness uniformity but also on monolayer s st tr ra ai in n uniformity. Only when both thickness and strain are uniform over a significant fraction (> 40%) of the device active area does the mobility exceed 1000 cm 2 /V-s. Additionally, we achieve high mobility epitaxial graphene (18,100 cm 2 /V-s at room temperature) on the C-face of SiC [SiC(000-1)] and show that carrier mobility depends strongly on the graphene layer stacking. These findings provide a means to rapidly estimate carrier mobility and provide a guide to achieve very high mobility in epitaxial graphene. Our results suggest that ultra-high mobilities (>50,000 cm 2 /V-s) are achievable via the controlled formation of uniform, rotationally faulted epitaxial graphene.The recent success of graphene transistor operation in the giga-hertz range has solidified the potential of this material for high speed electronic applications. 1,2 Realization of graphene technologies at commercial scales, however, necessitates large-area graphene production, as well as the ability to rapidly characterize its structural and electronic quality. Graphene films can be produced by mechanical exfoliation from bulk graphite, 3,4 reduction of graphite-oxide, 5,6 chemical vapor deposition on catalytic films, 7 or via Si-sublimation from bulk SiC substrates. 8 9, -10,11, 12 The last technique currently appears to hold the most promise for large-area electronic grade graphene, and already shows tremendous potential for high-frequency device technologies. 2 Nevertheless, precise control of the graphene electronic properties (i.e. mobility) over large areas is necessary to enable graphene-based technological applications. Realization of such control will come through an intimate understanding of the process-propertyperformance relationship and the role that graphene thickness, strain, and layer stacking plays in this relationship over very large areas up to full wafers. Of the characterization techniques used for layer thickness determination, 13 ,14,15, -16,17,18, 19 Raman spectroscopy is arguably the simplest and fastest, especially for exploring monolayer EG on SiC(0001) (referred to as EG Si )and EG layer stacking on SiC(000-1) (referred to as EG c ). [15][16][17][18][19] Characterization of EG via Raman spectroscopy requires fitting the 2D Raman peak. 15,16,20 Raman spectra of EG Si fit by one or four Lorentzian functions are characteristic of monolayer or bilayer graphene, respectively. 15 Figure 1a demonstrates layer thickness evaluation for monolayer and bilayer EG Si via Lorentzian fitting of the 2D Raman spectra. To further validate these thickness measurements, cross-sectional transmission electron microscopy (TEM) was performed (Fig. 1b,c). The TEM micrographs in Fig.1b,c include a transition layer (Layer 0), which is in dire...

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confidence: 93%

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confidence: 99%

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confidence: 99%

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Correlating Raman Spectral Signatures with Carrier Mobility in Epitaxial Graphene: A Guide to Achieving High Mobility on the Wafer Scale

et al. 2009

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“…The lack of AB stacking ( Figure 3d) reduces electronic coupling between the graphene layers, so that bilayer graphene in this configuration has electronic properties similar to that of monolayer graphene. [30][31][32] Supporting Information section 6), which corresponds to a single layer. It is accepted that the electronic structure and density of states play a key role in heterogeneous ET rates, 22,33 and these results show that different graphene layers (monolayer and bilayer), with closely similar band structures, behave analogously in terms of electrochemistry.…”

Section: Introductionmentioning

confidence: 99%

Structural Correlations in Heterogeneous Electron Transfer at Monolayer and Multilayer Graphene Electrodes

et al. 2012

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ABSTRACT:As a new form of carbon, graphene is attracting intense interest as an electrode material with widespread applications. In the present study, the heterogeneous electron transfer (ET) activity of graphene is investigated using scanning electrochemical cell microscopy (SECCM), which allows electrochemical currents to be mapped at high spatial resolution across a surface for correlation with the corresponding structure and properties of the graphene surface. We establish that the rate of heterogeneous ET at graphene increases systematically with the number of graphene layers, and show that the stacking in multilayers also has a subtle influence on ET kinetics.Graphene-based materials are having a huge impact in electrochemistry and electrochemical technologies, with promising applications in areas such as supercapacitors, 1 batteries, 2 electrocatalytic supports, 3 sensors for electroanalysis 4 and transparent electrodes. 5 These important technologies typically use graphene produced by chemical vapor deposition (CVD) 6 and other scalable methods, yet important fundamentals questions concerning heterogeneous electron transfer (ET) at such materials -intrinsic to many of these applications-remain to be addressed. Electrical measurements have revealed that the electron mobility 7 and the electronic band structure 8 are sensitive to the number of graphene layers and their stacking order, with implications for electrochemistry. In this communication, we thus seek to elucidate how both the number of graphene layers and arrangement of the layers influence heterogeneous ET kinetics.Graphene grown by CVD on nickel substrates 9 (see Supporting Information section 1) was optimal for the present study because it presents a heterogeneous continuous layer of microsized multilayered flakes, which can be addressed with high resolution scanning electrochemical cell microscopy (SECCM). [10][11][12][13] Thus, on one sample it is possible to make thousands of individual electrochemical (EC) measurements at different locations and relate these to the corresponding graphene structure. This provides datasets on a scale that would be unfeasible with conventional photolithographic techniques of the type employed in recent EC studies of exfoliated graphene. [14][15][16] In order to study the unambiguous electrochemical response of graphene without any interference from a conductive substrate, CVD graphene layers were transferred to a silicon substrate with a 300 nm thermal grown oxide layer. This substrate allowed optical visualization and identification of the morphological film features characteristic of graphene, 17,18 for direct correlation with the local electrochemistry. Importantly, the approach described herein makes possible the study of graphene surfaces with minimal intrusion and avoids the need for any post-processing lithographic step, which may result in unavoidable damage and possible interference of residues. 19 Ferrocene-derivatives have proven particularly suitable for the study of the ET activity of sp 2 ca...

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“…[7][8][9] The latter with rotationally stacked layers exhibits properties similar to SLG. [10][11][12] Moreover, it shows improved charge carrier mobility. 13 Furthermore, it has been observed that the rotationally stacked BLG decouples its electronic structure and preserves the intrinsic properties of SLG.…”

Section: Introductionmentioning

confidence: 99%

Control of layer stacking in CVD graphene under quasi-static condition

Subhedar

Sharma

Dhakate

2015

Phys. Chem. Chem. Phys.

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The type of layer stacking in bilayer graphene has a significant influence on its electronic properties because of the contrast nature of layer coupling. Herein, different geometries of the reaction site for the growth of bilayer graphene by the chemical vapor deposition (CVD) technique and their effects on the nature of layer stacking are investigated. Micro-Raman mapping and curve fitting analysis confirmed the type of layer stacking for the CVD grown bilayer graphene. The samples grown with sandwiched structure such as quartz/Cu foil/quartz along with a spacer, between the two quartz plates to create a sealed space, resulted in Bernal or AB stacked bilayer graphene while the sample sandwiched without a spacer produced the twisted bilayer graphene. The contrast difference in the layer stacking is a consequence of the difference in the growth mechanism associated with different geometries of the reaction site. The diffusion dominated process under quasi-static control is responsible for the growth of twisted bilayer graphene in sandwiched geometry while surface controlled growth with ample and continual supply of carbon in sandwiched geometry along with a spacer, leads to AB stacked bilayer graphene. Through this new approach, an efficient technique is presented to control the nature of layer stacking.

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Why Multilayer Graphene on4H−SiC(0001¯)Behaves Like a Single Sheet of Graphene

Cited by 792 publications

References 31 publications

Correlating Raman Spectral Signatures with Carrier Mobility in Epitaxial Graphene: A Guide to Achieving High Mobility on the Wafer Scale

Correlating Raman Spectral Signatures with Carrier Mobility in Epitaxial Graphene: A Guide to Achieving High Mobility on the Wafer Scale

Structural Correlations in Heterogeneous Electron Transfer at Monolayer and Multilayer Graphene Electrodes

Control of layer stacking in CVD graphene under quasi-static condition

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