scholarly journals Possible pair-graphene structures govern the thermodynamic properties of arbitrarily stacked few-layer graphene

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong Sun ◽  
Kenta Kirimoto ◽  
Tsuyoshi Takase ◽  
Daichi Eto ◽  
Shohei Yoshimura ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Lattice Deformation ◽  
Stable Pair ◽  
Stick Slip ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Stacking Order ◽  
Few Layer Graphene

AbstractThe thermodynamic properties of few-layer graphene arbitrarily stacked on LiNbO3 crystal were characterized by measuring the parameters of a surface acoustic wave as it passed through the graphene/LiNbO3 interface. The parameters considered included the propagation velocity, frequency, and attenuation. Mono-, bi-, tri-, tetra-, and penta-layer graphene samples were prepared by transferring individual graphene layers onto LiNbO3 crystal surfaces at room temperature. Intra-layer lattice deformation was observed in all five samples. Further inter-layer lattice deformation was confirmed in samples with odd numbers of layers. The inter-layer lattice deformation caused stick–slip friction at the graphene/LiNbO3 interface near the temperature at which the layers were stacked. The thermal expansion coefficient of the deformed few-layer graphene transitioned from positive to negative as the number of layers increased. To explain the experimental results, we proposed a few-layer graphene even–odd layer number stacking order effect. A stable pair-graphene structure formed preferentially in the few-layer graphene. In even-layer graphene, the pair-graphene structure formed directly on the LiNbO3 substrate. Contrasting phenomena were noted with odd-layer graphene. Single-layer graphene was bound to the substrate after the stable pair-graphene structure was formed. The pair-graphene structure affected the stacking order and inter-layer lattice deformation of few-layer graphene substantially.

scholarly journals Preparation of Copper Surface for the Synthesis of Single-Layer Graphene

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1071
Author(s):  
Ivan Kondrashov ◽  
Maxim Komlenok ◽  
Pavel Pivovarov ◽  
Sergey Savin ◽  
Elena Obraztsova ◽  
...  
Keyword(s):  
Copper Foil ◽  
Single Layer ◽  
Chemical Vapor ◽  
Copper Surface ◽  
Single Layer Graphene ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Additional Layer ◽  
Graphene Synthesis ◽  
Few Layer Graphene

Chemical vapor deposition synthesis of graphene on copper foil from methane is the most promising technology for industrial production. However, an important problem of the formation of the additional graphene layers during synthesis arises due to the strong roughness of the initial copper foil. In this paper, various approaches are demonstrated to form a smooth copper surface before graphene synthesis to reduce the amount of few layer graphene islands. Six methods of surface processing of copper foils are studied and the decrease of the roughness from 250 to as low as 80 nm is achieved. The correlation between foil roughness and the formation of the additional layer is demonstrated. Under optimized conditions of surface treatment, the content of the additional graphene layer drops from 9 to 2.1%. The quality and the number of layers of synthesized graphene are analyzed by Raman spectroscopy, scanning electron microscopy and measurements of charge mobility.

scholarly journals Characterizing the maximum number of layers in chemically exfoliated graphene

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Péter Szirmai ◽  
Bence G. Márkus ◽  
Julio C. Chacón-Torres ◽  
Philipp Eckerlein ◽  
Konstantin Edelthalhammer ◽  
...  
Keyword(s):  
Single Layer ◽  
Vapour Phase ◽  
Single Layer Graphene ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Exfoliated Graphene ◽  
Upper Limit ◽  
Number Of Layers ◽  
Graphene Flakes ◽  
Few Layer Graphene

AbstractAn efficient route to synthesize macroscopic amounts of graphene is highly desired and bulk characterization of such samples, in terms of the number of layers, is equally important. We present a Raman spectroscopy-based method to determine the typical upper limit of the number of graphene layers in chemically exfoliated graphene. We utilize a controlled vapour-phase potassium intercalation technique and identify a lightly doped stage, where the Raman modes of undoped and doped few-layer graphene flakes coexist. The spectra can be unambiguously distinguished from alkali doped graphite, and modeling with the typical upper limit of the layers yields an upper limit of flake thickness of five layers with a significant single-layer graphene content. Complementary statistical AFM measurements on individual few-layer graphene flakes find a consistent distribution of the layer numbers.

Thermal Conductivity Reduction in Few-Layer Graphene

2011 ◽  
Author(s):  
Dhruv Singh ◽  
Jayathi Y. Murthy ◽  
Timothy S. Fisher
Keyword(s):  
Thermal Conductivity ◽  
Weak Coupling ◽  
Phonon Scattering ◽  
Single Layer ◽  
Acoustic Mode ◽  
Single Layer Graphene ◽  
Boltzmann Transport ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Few Layer Graphene

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent. The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. The highly restrictive selection rule that leads to a high thermal conductivity of ZA phonons in single-layer graphene is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that the decrease in thermal conductivity is mainly caused by decreased contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. Moreover, the extent of reduction is largest when going from single to bilayer graphene and saturates for four layers. The results compare remarkably well over the entire temperature range with measurements of of graphene and graphite.

Image Processing To Aid in Graphene Detection

2014 ◽  
Vol 1702 ◽  
Author(s):  
Ryan D. Gorby ◽  
Lihong (Heidi) Jiao
Keyword(s):  
Image Processing ◽  
Single Layer ◽  
Optical Microscope ◽  
Single Layer Graphene ◽  
Camera System ◽  
Layer Graphene ◽  
Sophisticated Equipment ◽  
Processing Software ◽  
Image Processing Software ◽  
Few Layer Graphene

ABSTRACTQualitative techniques for the detection of graphene on a Si/SiO2 substrate, without the use of sophisticated equipment, are presented. Once calibrated, this technique can be used to detect Single Layer Graphene (SLG) and Few Layer Graphene (FLG) with the use of an inexpensive optical microscope (OM), OM camera system, and image processing software. This technique could be transferred to graphene deposited on other substrates or other 2-D materials with minor updates to mathematical theory.

Zur Kristallchemie von Graphen und Graphit

2009 ◽  
Vol 66 (1) ◽  
pp. 81-83
Author(s):  
M. Trömel
Keyword(s):  
Crystal Structure ◽  
Chemical Properties ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Chemical Bonds ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Closest Packing ◽  
Weak Chemical ◽  
And Chemical Properties

The crystal structure of single-layer graphene in comparison to graphite is discussed with regard to its crystallographic and chemical properties. In both of these polymorphs of carbon, the atomic volume of carbon, reduced to the closest packing of atoms, is practically the same and considerably smaller than in diamond. This indicates pentavalent carbon in graphene as well as in graphite. The observed elastic corrugations of the graphene layers which probably cause their amazing rigidity seem to be due to numerous weak chemical bonds within the layers.

scholarly journals Influence of Different Copper Treatment on the Formation of Single-Layer Graphene by CVD Method

2020 ◽  
Vol 4 (1) ◽  
pp. 14
Author(s):  
Ivan Kondrashov ◽  
Maxim Komlenok ◽  
Pavel Pivovarov ◽  
Sergei Savin ◽  
Elena Obraztsova ◽  
...  
Keyword(s):  
Copper Foil ◽  
Single Layer ◽  
Chemical Vapor ◽  
Copper Surface ◽  
Single Layer Graphene ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Graphene Synthesis ◽  
Number Of Layers ◽  
Optimized Conditions

Chemical vapor deposition synthesis of graphene on copper foil from methane is the most promising technology for industrial production. However, an important problem of the formation of the second and subsequent graphene layers during synthesis arises due to the strong roughness of the initial copper foil. Here we demonstrate the various approaches to prepare a smooth copper surface before graphene synthesis to reduce the formation of multi-layer graphene islands. Six methods of surface processing of copper foils are studied, and the decrease of the roughness from 250 to as low as 80 nm is achieved. The correlation between roughness and the formation of multi-layer graphene is demonstrated. Under optimized conditions of surface treatment, the content of the multi-layer graphene islands drops from 9% to 2.1%. The quality and the number of layers of synthesized graphene are analyzed by Raman spectroscopy, scanning electron microscopy, and measurements of charge mobility.

DNA Gating effect from single layer graphene

2011 ◽  
Vol 1344 ◽  
Author(s):  
Jian Lin ◽  
Desalegne Teweldebrhan ◽  
Khalid Ashraf ◽  
Guanxiong Liu ◽  
Xiaoye Jing ◽  
...  
Keyword(s):  
Dirac Point ◽  
Full Width Half Maximum ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Hole Density ◽  
Voltage Measurement ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Current Voltage ◽  
Gating Effect

ABSTRACTIn this letter, single stranded Deoxyribonucleic Acids (ssDNA) are found to act as negative potential gating agents that increase the hole density in single layer graphene (SLG). Current-voltage measurement of the hybrid ssDNA/graphene system indicates a shift in the Dirac point and “intrinsic” conductance after ssDNA is patterned. The effect of ssDNA is to increase the hole density in the graphene layer, which is calculated to be on the order of 1.8×1012 cm-2. This increased density is consistent with the Raman frequency shifts in the G-peak and 2D band positions and the corresponding changes in the G-peak full-width half maximum. This patterning of DNA on graphene layers could provide new avenues to modulate their electrical properties and for novel electronic devices.

First Principles Study of Interlayer Interaction Effect on Graphene Thermal Conductivity

2019 ◽  
Author(s):  
Yuan Dong ◽  
Chi Zhang ◽  
Chenghao Diao ◽  
Jian Lin
Keyword(s):  
Thermal Conductivity ◽  
Phonon Dispersion ◽  
Single Layer ◽  
Theoretical Aspect ◽  
Single Layer Graphene ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Multiple Layer ◽  
Phonon Properties ◽  
Vdw Interaction

Abstract It is known that the interlayer van der Waals (vdW) interactions will decrease the thermal conductivity of graphene. Single layer graphene (SLG) has the highest thermal conductivities, double layer graphene (DLG) would decrease to about half of the thermal conductivity of SLG. The graphite was measured to have a thermal conductivity of about 2000 W/m-K. Some research shows that graphite differs from SLG within a factor of 2, and DLG has almost the same thermal conductivity with graphite. In theoretical aspect, how to simulate the vdW interaction between graphene layers is a long existing problem. It is only until recently that the vdW interaction is still an active topic in first principle calculations. The popular methods include the Grimme’s DFT-D, vdW-DF and vdW-DFT-R methods. The vdW-DFT-R method was further optimized to increase accuracy by Hamada and was found to predict the most accurate interlayer distance between AB-stacked graphene in our recent study. The motivation of this work is to investigate the effect of vdW interaction on the thermal conductivity of multiple layer graphene from principles. We will calculate firstly the phonon dispersion relations of multiple layer graphene with the vdW interaction included. The obtained phonon properties and force constants will be combined with the ShengBTE method to calculate the thermal conductivity. The results show how vdW interaction causes the dimensional crossover of graphene thermal conductivity.

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