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The Raman active G mode in graphene exhibits strong coupling to electrons, yet the comprehensive treatment of this interaction in the calculation of its temperature-dependent Raman spectrum remains incomplete. In this study, we calculate…

Richness and complexity of Raman spectra related to graphene materials is established from years to decades, with, among others: the well-known G, D, 2D,... bands plus a plethora of weaker bands related to disorder behavior, doping, stress,…

The equilibrium optical phonons of graphene are well characterized in terms of anharmonicity and electron-phonon interactions, however their non-equilibrium properties in the presence of hot charge carriers are still not fully explored.…

Mesoscale and Nanoscale Physics · Physics 2018-02-15 C. Ferrante , A. Virga , L. Benfatto , M. Martinati , D. De Fazio , U. Sassi , C. Fasolato , A. K. Ott , P. Postorino , D. Yoon , G. Cerullo , F. Mauri , A. C. Ferrari , T. Scopigno

Graphite is a well-studied material with known electronic and optical properties. Graphene, on the other hand, which is just one layer of carbon atoms arranged in a hexagonal lattice, has been studied theoretically for quite some time but…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 F. Molitor , D. Graf , C. Stampfer , T. Ihn , K. Ensslin

We report that graphene films with thickness ranging from 1 to 7 layers can be controllably synthesized on the surface of polycrystalline copper by a chemical vapour deposition method. The number of layers of graphene is controlled…

We probe the local inhomogeneities of the electronic properties of graphene at the nanoscale using scanning probe microscopy techniques. First, we focus on the study of the electronic inhomogeneities caused by the graphene-substrate…

Mesoscale and Nanoscale Physics · Physics 2012-10-16 A. Castellanos-Gomez , Arramel , M. Wojtaszek , R. H. M. Smit , N. Tombros , N. Agraït , B. J. van Wees , G. Rubio-Bollinger

In this work we study the behavior of the optical phonon modes in bilayer graphene devices by applying top gate voltage, using Raman scattering. We observe the splitting of the Raman G band as we tune the Fermi level of the sample, which is…

Mesoscale and Nanoscale Physics · Physics 2012-06-07 D. L. Mafra , P. Gava , L. M. Malard , R. S. Borges , G. G. Silva , J. A. Leon , F. Plentz , F. Mauri , M. A. Pimenta

We calculate the double resonant (DR) Raman spectrum of graphene, and determine the lines associated to both phonon-defect processes, and two-phonons ones. Phonon and electronic dispersions reproduce calculations based on density functional…

Mesoscale and Nanoscale Physics · Physics 2011-07-26 Pedro Venezuela , Michele Lazzeri , Francesco Mauri

Avoiding charge density variations and impurities in graphene is vital for high-quality graphene-based devices. Here, we demonstrate an optical method using Raman 2D peak-split to monitor charge density variations in the range 1-25e10 cm-2.…

Applied Physics · Physics 2020-05-12 Zhuofa Chen , Nathan Ullberg , Mounika Vutukuru , David Barton , Anna K Swan

Direct, tunable coupling between individually assembled graphene layers is a next step towards designer two-dimensional (2D) crystal systems, with relevance for fundamental studies and technological applications. Here we describe the…

Since graphene, a single sheet of graphite, has all of its carbon atoms on the surface, its property is very sensitive to materials contacting the surface. Herein, we report novel Raman peaks ob-served in annealed graphene and elucidate…

Materials Science · Physics 2013-10-31 Jinpyo Hong , Min Kyu Park , Eun Jung Lee , DaeEung Lee , Dong Seok Hwang , Sunmin Ryu

The unique properties of graphene offer immense opportunities for applications to many scientific fields, as well as societal needs, beyond our present imagination. One of the important features of graphene is the relatively simple…

Materials Science · Physics 2018-04-27 Otakar Frank , Mildred S. Dresselhaus , Martin Kalbac

We perform Raman scattering experiments on natural graphite in magnetic fields up to 45 T, observing a series of peaks due to interband electronic excitations over a much broader magnetic field range than previously reported. We also…

Mesoscale and Nanoscale Physics · Physics 2012-03-14 Y. Kim , Y. Ma , A. Imambekov , N. G. Kalugin , A. Lombardo , A. C. Ferrari , J. Kono , D. Smirnov

We synthesize large-area graphene via atmospheric-pressure (AP) chemical vapor deposition (CVD) on copper, and transfer to SiO2 wafers. In contrast to low-pressure (LP) CVD on copper, optical contrast and atomic force microscopy…

Materials Science · Physics 2011-07-15 Daniel R. Lenski , Michael S. Fuhrer

We have investigated the effects of ozone treatment on graphene by Raman scattering. Sequential ozone short-exposure cycles resulted in increasing the $p$ doping levels as inferred from the blue shift of the 2$D$ and $G$ peak frequencies,…

Mesoscale and Nanoscale Physics · Physics 2015-05-19 F. Alzina , H. Tao , J. Moser , Y. Garcia , A. Bachtold , C. M. Sotomayor-Torres

Nanometer-scale graphene objects are attracting much research interest because of newly emerging properties originating from quantum confinement effects. We present Raman spectroscopy studies of graphene nanoribbons (GNRs) which are known…

Materials Science · Physics 2012-01-23 Sunmin Ryu , Janina Maultzsch , Melinda Y. Han , Philip Kim , Louis E. Brus

Though graphene has been intensively studied by Raman spectroscopy, in this letter, we report a study of second-order overtone and combinational Raman modes in an unexplored range of 1690-2150 cm-1 in nonsuspended commensurate (AB-stacked),…

Materials Science · Physics 2010-10-19 Chunxiao Cong , Ting Yu , Riichiro Saito

Strain can be used as an alternate way to tune the electronic properties of graphene. Here we demonstrate that it is possible to tune the uniform strain of graphene simply by changing the chemical vapor deposition growth temperature of…

Materials Science · Physics 2015-03-17 Victor Yu , Eric Whiteway , Jesse Maassen , Michael Hilke

The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interests. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties.…

Materials Science · Physics 2013-07-23 Ting Fung Chung , Tian Shen , Helin Cao , Luis A. Jauregui , Wei Wu , Qingkai Yu , David Newell , Yong P. Chen

Graphene is a material of great potential in a broad range of applications, for each of which specific tuning of the materials properties is required. This can be achieved, for example, by covalent functionalization. We have exploited two…