Structural and electronic properties of graphite layers grown on SiC(0001)

Seyller, Thomas; Emtsev, K. V.; Gao, Kun; Speck, Florian; Ley, L.; Tadich, Anton; Broekman, L.; Riley, J.D.; Leckey, Robert; Rader, O.; Varykhalov, A.; Shikin, A. M.

doi:10.1016/j.susc.2006.01.102

Cited by 186 publications

(113 citation statements)

References 33 publications

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“…This topography profile illustrates that the superlattice exhibits a constant value of D and remains in phase as it traverses the step edge, indicating that the relative rotation between the top two layers of graphene is constant across the step. The observation of a commensurate moiré superlattice spanning a step edge in the substrate supports the suggestion that FLG growth follows a carpet-like growth mechanism proposed by Seyller et al [154]. 7.5.9 Termination and energetics of a small moiré region Typically, the moiré regions in the FLG grown samples studied were large enough that the entire pattern could not be imaged within a single scan of dimension 1 × 1 µm 2 .…”

Section: I(v) Across a Moiré Regionsupporting

confidence: 80%

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

Biedermann¹

2009

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A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers).Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires 3 studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured-MWNTs and Ag 2 Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37±26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag 2 Ga nanoneedles have a greater optical scattering efficiency than MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag 2 Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag 2 Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3±1.0 GPa.Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q gas is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag 2 Ga nanoneedles is three times that of the MWNTs, the Ag 2 Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag 2 Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000....

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Section: I(v) Across a Moiré Regionsupporting

confidence: 80%

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

Biedermann¹

2009

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“…Thus large area graphene production process and ultimate control of the thickness to be a monolayer of graphene sheet, and it may be allowed for a few stack of graphene, will enormously contribute to the graphene electronics. One of possible candidate will be sublimation process on SiC (0001) hexagonal surface [10,11], where about 1800 ºC of high temperature annealing sublimated Si atoms and remained excess carbon produced a few layers of graphene. Another conventional method of graphene growth technique is chemical vapor reaction/deposition on a metal crystal such as Ni, Co, and Cu.…”

Section: Introductionmentioning

confidence: 99%

Graphitization at interface between amorphous carbon and liquid gallium for fabricating large area graphene sheets

Fujita

Ueki

Miyazawa

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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We have found that liquid gallium exhibits as a good graphitizing catalyst for a large area graphene sheet. While gallium and carbon are known to be an insoluble system, however, we have found that the catalytic reaction occurs at a very narrow interfacial region between amorphous carbon and liquid gallium. Amorphous carbon film was transformed into graphite layer composed of a few layers of graphene sheet. These thin graphene film can be easily transferred into silicon substrate through the intermediation of PDMS rubber stamping.

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“…Ct, 68.47.Fg, The last years have witnessed an explosion of interest in the prospect of graphene-based nanometer-scale electronics [1,2,3,4]. Graphene, a single hexagonally ordered layer of carbon atoms, has a unique electronic band structure with the conic "Dirac points" at two inequivalent corners of the two-dimensional Brillouin zone.…”

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confidence: 99%

Ab InitioStudy of Graphene on SiC

2007

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Employing density-functional calculations we study single and double graphene layers on Si-and C-terminated 1 × 1 -6H-SiC surfaces. We show that, in contrast to earlier assumptions, the first carbon layer is covalently bonded to the substrate, and cannot be responsible for the graphenetype electronic spectrum observed experimentally. The characteristic spectrum of free-standing graphene appears with the second carbon layer, which exhibits a weak van der Waals bonding to the underlying structure. For Si-terminated substrate, the interface is metallic, whereas on C-face it is semiconducting or semimetallic for single or double graphene coverage, respectively.PACS numbers: 68.35. Ct, 68.47.Fg, The last years have witnessed an explosion of interest in the prospect of graphene-based nanometer-scale electronics [1,2,3,4]. Graphene, a single hexagonally ordered layer of carbon atoms, has a unique electronic band structure with the conic "Dirac points" at two inequivalent corners of the two-dimensional Brillouin zone. The electron mobility may be very high and lateral patterning with standard lithography methods allows device fabrication [1]. Two ways of obtaining graphene samples have been used up to now. In the first "mechanical" method, the carbon monolayers are mechanically split off the bulk graphite crystals and deposited onto a SiO 2 /Si substrate [4]. This way an almost "freestanding" graphene is produced, since the carbon monolayer is practically not coupled to the substrate. The second method uses epitaxial growth of graphite on singlecrystal silicon carbide (SiC). The ultrathin graphite layer is formed by vacuum graphitization due to Si depletion of the SiC surface [5]. This method has apparent technological advantages over the "mechanical" method, however it does not guarantee that an ultrathin graphite (or graphene) layer is electronically isolated from the substrate. Moreover, one expects a covalent coupling between both which may strongly modify the electronic properties of the graphene overlayer. Yet, experiments show that the transport properties of the interface are dominated by a single epitaxial graphene layer [1,2]. Most surprisingly, the electronic spectrum seems not to be affected much by the substrate. As in free-standing graphene one observes the "Dirac points" with the linear dispersion relation around them. The electron dynamics is governed by a Dirac-Weyl Hamiltonian with the Fermi velocity of graphene replacing the speed of light. This leads to an unusual sequence of Landau levels in a magnetic field and hence to peculiar features in the quantum Hall effect [1,4].

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Structural and electronic properties of graphite layers grown on SiC(0001)

Cited by 186 publications

References 33 publications

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

Graphitization at interface between amorphous carbon and liquid gallium for fabricating large area graphene sheets

Ab InitioStudy of Graphene on SiC

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