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Abdelkarim Ouerghi - One of the best experts on this subject based on the ideXlab platform.
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Large area molybdenum disulphide- Epitaxial Graphene vertical Van der Waals heterostructures
Scientific Reports, 2016Co-Authors: Debora Pierucci, Patrick Le Fèvre, Haikel Sediri, A. T. Charlie Johnson, Emmanuel Lhuillier, François Bertran, Hugo Henck, Carl H. Naylor, Adrian Balan, Julien E. Rault, Yannick J. Dappe, Abdelkarim OuerghiAbstract:Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as Epitaxial Graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-Graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto Epitaxial Graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with Epitaxial Graphene. A downshift of the Raman 2D band of the Graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to Epitaxial Graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.
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Laterally inhomogeneous Au intercalation in Epitaxial Graphene on SiC(0001): a multimethod electron microscopy study
2016Co-Authors: C. Mathieu, Tevfik Onur Mentes, Emiliano Pallecchi, Andrea Locatelli, Gilles Patriarche, Rachid Belkhou, Abdelkarim OuerghiAbstract:Epitaxial Graphene is of particular interest because of its tunable electronic structure. One important approach to tune the electronic properties of Graphene relays on intercalating atomic species between Graphene and the topmost silicon carbide layer. Here, we investigated the morphology and electronic structure of gold-intercalated Epitaxial Graphene using a multitechnique approach combining spectroscopic photoemission low-energy electron microscopy (SPELEEM) for chemical and structural characterization at mesoscopic length scale and with transmission electron microscopy (STEM) at the atomic level. Deposition of gold on ex situ prepared Graphene on SiC(0 0 0 1) results in the partial intercalation of Au adatoms under Graphene, with the formation of a buffer layer of variable thickness. Gold has also shown to aggregate in nanometer-sized clusters lying on top of the same Graphene film. X-ray photo-emission electron microscopy measurements indicate that Au induces only small changes in the doping of the Graphene layer, which does not develop a quasi free-standing behavior.
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Sharp interface in Epitaxial Graphene layers on 3C-SiC(100)/Si(100) wafers
Physical Review B: Condensed Matter and Materials Physics, 2011Co-Authors: Abdelkarim Ouerghi, Marc Portail, R. Belkhou, M. Ridene, A. Balan, A. Barbier, N. Gogneau, A. Michon, S. Latil, P. JegouAbstract:Graphene ranks highly as a promising material for future nanoelectronic devices because of its exceptional electron-transport properties. It appears as a material of choice for high-frequency applications. We report the growth and structure of Epitaxial Graphene layers on 3C-SiC(100)/Si(100) wafers using low-energy electron microscopy. Selective-area low-energy electron diffraction highlights the presence of two Graphene domains, rotated by ±15◦ with respect to the SiC lattice. Micro-Raman spectroscopy demonstrates the characteristic signature of few layer Graphene on the SiC. X-ray photoemission spectroscopy evidences a sharp interface between Graphene and 3C-SiC(100). It appears that Epitaxial Graphene layers obtained on 3C-SiC(100)/Si(100) have properties similar to those obtained using classical 6H or 4H-SiC substrates with the advantage of being compatible with the current Si processing technology
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Epitaxial Graphene on cubic sic 111 si 111 substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)/Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
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Epitaxial Graphene on cubic SiC(111)/Si(111) substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)∕Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
Claire Berger - One of the best experts on this subject based on the ideXlab platform.
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EpiGraphene : Epitaxial Graphene on silicon carbide
2017Co-Authors: Claire Berger, Edward Conrad, Walt De HeerAbstract:This article presents a review of Epitaxial Graphene on silicon carbide, from fabrication to properties, put in the context of other forms of Graphene
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Epitaxial Graphene on SiC: 2D sheets, selective growth and nanoribbons
2017Co-Authors: Claire Berger, James Palmer, John Hankinson, Dogukan Deniz, Jamey Gigliotti, Jean-philippe Turmaud, Renaud Puybaret, Abdallah Ougazzaden, Anton Sidorov, Z. JiangAbstract:Epitaxial Graphene grown on SiC by the confinement controlled sublimation method is reviewed, with an emphasis on multilayer and monolayer Epitaxial Graphene on the carbon face of 4H-SiC and on directed and selectively grown structures under growth-arresting or growth-enhancing masks. Recent developments in the growth of templated Graphene nanostructures are also presented, as exemplified by tens of micron long very well confined and isolated 20-40nm wide Graphene ribbons. Scheme for large scale integration of ribbon arrays with Si wafer is also presented.
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Exceptional ballistic transport in Epitaxial Graphene nanoribbons
Nature, 2014Co-Authors: Jens Baringhaus, Claire Berger, Ming Ruan, Z. Jiang, Edward Conrad, Frederik Edler, Antonio Tejeda, Muriel Sicot, Amina Taleb Ibrahimi, Christoph TegenkampAbstract:Graphene electronics has motivated much of Graphene science for the past decade. A primary goal was to develop high mobility semiconducting Graphene with a band gap that is large enough for high performance applications. Graphene ribbons were thought to be semiconductors with these properties, however efforts to produce ribbons with useful bandgaps and high mobility has had limited success. We show here that high quality Epitaxial Graphene nanoribbons 40 nm in width, with annealed edges, grown on sidewall SiC are not semiconductors, but single channel room temperature ballistic conductors for lengths up to at least 16 micrometers. Mobilities exceeding one million corresponding to a sheet resistance below 1 Ohm have been observed, thereby surpassing two dimensional Graphene by 3 orders of magnitude and theoretical predictions for perfect Graphene by more than a factor of 10. The Graphene ribbons behave as electronic waveguides or quantum dots. We show that transport in these ribbons is dominated by two components of the ground state transverse waveguide mode, one that is ballistic and temperature independent, and a second thermally activated component that appears to be ballistic at room temperature and insulating at cryogenic temperatures. At room temperature the resistance of both components abruptly increases with increasing length, one at a length of 160 nm and the other at 16 micrometers. These properties appear to be related to the lowest energy quantum states in the charge neutral ribbons. Since Epitaxial Graphene nanoribbons are readily produced by the thousands, their room temperature ballistic transport properties can be used in advanced nanoelectronics as well.
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Local work function measurements of plasma-fluorinated Epitaxial Graphene
Applied Physics Letters, 2014Co-Authors: Sonam Sherpa, Claire Berger, Walt A. De Heer, Jan Kunc, Galit Levitin, Dennis HessAbstract:Plasma-fluorination is an attractive route toward the work function engineering of Graphene. The effect of surface topography of Epitaxial Graphene grown on silicon carbide on the increase in work function after plasma-fluorination was investigated using scanning Kelvin probe microscopy. Results of these studies demonstrate the ability of plasma-treatments to functionalize Epitaxial Graphene without significant surface roughening. For few-layer Epitaxial Graphene on the Si-face, work function distribution corresponds to its surface topography. A bimodal distribution is observed before and after fluorination and the separation between the two modes widens after the fluorination. For multi-layer Epitaxial Graphene on the C-face, no correlation is observed between the work function distribution and the surface topography. After fluorination, the work function is fairly uniform except in few peeled off areas that show a stronger work function contrast.
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Wafer bonding solution to Epitaxial Graphene - silicon integration
Journal of Physics D: Applied Physics, 2014Co-Authors: Rui Dong, Zelei Guo, Claire Berger, James Palmer, Ming Ruan, John Hankinson, Jan Kunc, Swapan K Bhattacharya, Walt A. De HeerAbstract:The development of Graphene electronics requires the integration of Graphene devices with Si-CMOS technology. Most strategies involve the transfer of Graphene sheets onto silicon, with the inherent difficulties of clean transfer and subsequent Graphene nano-patterning that degrades considerably the electronic mobility of nanopatterned Graphene. Epitaxial Graphene (EG) by contrast is grown on an essentially perfect crystalline (semi-insulating) surface, and Graphene nanostructures with exceptional properties have been realized by a selective growth process on tailored SiC surface that requires no Graphene patterning. However, the temperatures required in this structured growth process are too high for silicon technology. Here we demonstrate a new Graphene to Si integration strategy, with a bonded and interconnected compact double-wafer structure. Using silicon-on-insulator technology (SOI) a thin monocrystalline silicon layer ready for CMOS processing is applied on top of Epitaxial Graphene on SiC. The parallel Si and Graphene platforms are interconnected by metal vias. This method inspired by the industrial development of 3d hyper-integration stacking thin-film electronic devices preserves the advantages of Epitaxial Graphene and enables the full spectrum of CMOS processing.
Walt A. De Heer - One of the best experts on this subject based on the ideXlab platform.
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Local work function measurements of plasma-fluorinated Epitaxial Graphene
Applied Physics Letters, 2014Co-Authors: Sonam Sherpa, Claire Berger, Walt A. De Heer, Jan Kunc, Galit Levitin, Dennis HessAbstract:Plasma-fluorination is an attractive route toward the work function engineering of Graphene. The effect of surface topography of Epitaxial Graphene grown on silicon carbide on the increase in work function after plasma-fluorination was investigated using scanning Kelvin probe microscopy. Results of these studies demonstrate the ability of plasma-treatments to functionalize Epitaxial Graphene without significant surface roughening. For few-layer Epitaxial Graphene on the Si-face, work function distribution corresponds to its surface topography. A bimodal distribution is observed before and after fluorination and the separation between the two modes widens after the fluorination. For multi-layer Epitaxial Graphene on the C-face, no correlation is observed between the work function distribution and the surface topography. After fluorination, the work function is fairly uniform except in few peeled off areas that show a stronger work function contrast.
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Wafer bonding solution to Epitaxial Graphene - silicon integration
Journal of Physics D: Applied Physics, 2014Co-Authors: Rui Dong, Zelei Guo, Claire Berger, James Palmer, Ming Ruan, John Hankinson, Jan Kunc, Swapan K Bhattacharya, Walt A. De HeerAbstract:The development of Graphene electronics requires the integration of Graphene devices with Si-CMOS technology. Most strategies involve the transfer of Graphene sheets onto silicon, with the inherent difficulties of clean transfer and subsequent Graphene nano-patterning that degrades considerably the electronic mobility of nanopatterned Graphene. Epitaxial Graphene (EG) by contrast is grown on an essentially perfect crystalline (semi-insulating) surface, and Graphene nanostructures with exceptional properties have been realized by a selective growth process on tailored SiC surface that requires no Graphene patterning. However, the temperatures required in this structured growth process are too high for silicon technology. Here we demonstrate a new Graphene to Si integration strategy, with a bonded and interconnected compact double-wafer structure. Using silicon-on-insulator technology (SOI) a thin monocrystalline silicon layer ready for CMOS processing is applied on top of Epitaxial Graphene on SiC. The parallel Si and Graphene platforms are interconnected by metal vias. This method inspired by the industrial development of 3d hyper-integration stacking thin-film electronic devices preserves the advantages of Epitaxial Graphene and enables the full spectrum of CMOS processing.
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Electronic cooling in multilayer Epitaxial Graphene
CLEO: 2013, 2013Co-Authors: Momchil T. Mihnev, Charles Divin, A H Macdonald, Claire Berger, John R. Tolsma, Walt A. De Heer, Theodore B. NorrisAbstract:Using ultrafast optical-pump terahertz-probe spectroscopy, we measure the low-temperature electronic cooling in multilayer Epitaxial Graphene and develop a theory of hot-carrier equilibration based on interlayer energy transfer via screened Coulomb interactions.
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Epitaxial Graphene on silicon carbide: Introduction to structured Graphene
MRS Bulletin, 2012Co-Authors: Ming Ruan, Zelei Guo, Claire Berger, James Palmer, Rui Dong, John Hankinson, Walt A. De HeerAbstract:We present an introduction to the rapidly growing field of Epitaxial Graphene on silicon carbide, tracing its development from the original proof-of-concept experiments a decade ago to its present, highly evolved state. The potential of Epitaxial Graphene as a new electronic material is now being recognized. Whether the ultimate promise of Graphene-based electronics will ever be realized remains an open question. Silicon electronics is based on single-crystal substrates that allow reliable patterning on the nanoscale, which is an absolute requirement for any new electronic material. That is why Epitaxial Graphene is based on single-crystal silicon carbide. We also present recent results on nanopatterned Graphene produced by etching the silicon carbide before annealing so that the Graphene structures are produced in their final shapes. This avoids postannealing patterning, which is known to greatly affect transport properties on the nanoscale. Creating such structured Graphene is an elegant method for avoiding pervasive patterning problems.
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Evidence for Interlayer Electronic Coupling in Multilayer Epitaxial Graphene from Polarization Dependent Coherently Controlled Photocurrent Generation
Physical Review B: Condensed Matter and Materials Physics, 2012Co-Authors: Dong Sun, Phillip N. First, Claire Berger, Momchil T. Mihnev, Walt A. De Heer, Julien Rioux, J. E. Sipe, Yang Zou, Theodore B. NorrisAbstract:Most experimental studies to date of multilayer Epitaxial Graphene on C-face SiC have indicated that the electronic states of different layers are decoupled as a consequence of rotational stacking. We have measured the third order nonlinear tensor in Epitaxial Graphene as a novel approach to probe interlayer electronic coupling, by studying THz emission from coherently controlled photocurrents as a function of the optical pump and THz beam polarizations. We find that the polarization dependence of the coherently controlled THz emission expected from perfectly uncoupled layers, i.e. a single Graphene sheet, is not observed. We hypothesize that the observed angular dependence arises from weak coupling between the layers; a model calculation of the angular dependence treating the multilayer structure as a stack of independent bilayers with variable interlayer coupling qualitatively reproduces the polarization dependence, providing evidence for coupling.
Thierry Chassagne - One of the best experts on this subject based on the ideXlab platform.
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Epitaxial Graphene on cubic sic 111 si 111 substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)/Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
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Epitaxial Graphene on cubic SiC(111)/Si(111) substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)∕Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
Marc Portail - One of the best experts on this subject based on the ideXlab platform.
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Sharp interface in Epitaxial Graphene layers on 3C-SiC(100)/Si(100) wafers
Physical Review B: Condensed Matter and Materials Physics, 2011Co-Authors: Abdelkarim Ouerghi, Marc Portail, R. Belkhou, M. Ridene, A. Balan, A. Barbier, N. Gogneau, A. Michon, S. Latil, P. JegouAbstract:Graphene ranks highly as a promising material for future nanoelectronic devices because of its exceptional electron-transport properties. It appears as a material of choice for high-frequency applications. We report the growth and structure of Epitaxial Graphene layers on 3C-SiC(100)/Si(100) wafers using low-energy electron microscopy. Selective-area low-energy electron diffraction highlights the presence of two Graphene domains, rotated by ±15◦ with respect to the SiC lattice. Micro-Raman spectroscopy demonstrates the characteristic signature of few layer Graphene on the SiC. X-ray photoemission spectroscopy evidences a sharp interface between Graphene and 3C-SiC(100). It appears that Epitaxial Graphene layers obtained on 3C-SiC(100)/Si(100) have properties similar to those obtained using classical 6H or 4H-SiC substrates with the advantage of being compatible with the current Si processing technology
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Epitaxial Graphene on cubic sic 111 si 111 substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)/Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
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Epitaxial Graphene on cubic SiC(111)/Si(111) substrate
Applied Physics Letters, 2010Co-Authors: Abdelkarim Ouerghi, Laurent Travers, Jacques Gierak, Abdelkader Kahouli, D. Lucot, A. Shukla, Pascale Jégou, Josep Peñuelas, Marc Portail, Thierry ChassagneAbstract:Epitaxial Graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of Epitaxial Graphene films on 3C-SiC(111)∕Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer Graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
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Epitaxial Graphene on 3C-SiC(111) pseudosubstrate: Structural and electronic properties
Physical Review B: Condensed Matter and Materials Physics, 2010Co-Authors: Abdelkarim Ouerghi, Marc Portail, M. Marangolo, R. Belkhou, S. El Moussaoui, M. G. Silly, Mahmoud Eddrief, L. Largeau, B. Fain, F. SirottiAbstract:Structural and electronic properties of Epitaxial Graphene on 3C-SiC(111) pseudosubstrate epilayers on silicon was investigated in detail by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), scanning transmission electron microscopy (STEM), and synchrotron angle-resolved photoemission spectroscopy (ARPES). The graphitization process has been observed by distinct features in the atomically resolved STM images and abrupt interface with the number of stacked-Graphene layer has been revealed in STEM image. Two different types of carbon atom networks, honeycomb and one sublattice, were atomically resolved by STM. Electronic properties and band structures of the Epitaxial Graphene are examined with angle-resolved photoemission spectroscopy, showing linear band dispersion K point of the Brillouin zone, with Dirac point about 500 meV below the Fermi level (E-F). These findings are of relevance for various potential applications based on Graphene-SiC/Si(111) structures.