Tuning the electrical properties of exfoliated graphene layers using deep ultraviolet irradiation

2014 ◽  
Vol 2 (27) ◽  
pp. 5404-5410 ◽  
Author(s):  
M. Z. Iqbal ◽  
M. F. Khan ◽  
M. W. Iqbal ◽  
Jonghwa Eom
Keyword(s):  
Electrical Properties ◽  
Ultraviolet Irradiation ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Graphene Bilayer ◽  
Graphene Layers ◽  
Exfoliated Graphene ◽  
Deep Ultraviolet ◽  
Trilayer Graphene ◽  
Unique Band

Deep ultraviolet irradiation tunes the electronic properties of mechanically exfoliated single-layer graphene, bilayer graphene, and trilayer graphene while maintaining their unique band structure and electrical properties.

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.

Deep UV Raman Spectroscopy of Epitaxial Graphenes on Vicinal 6H-SiC Substrates

2010 ◽  
Vol 645-648 ◽  
pp. 611-614
Author(s):  
Susumu Kamoi ◽  
Noriyuki Hasuike ◽  
Kenji Kisoda ◽  
Hiroshi Harima ◽  
Kouhei Morita ◽  
...  
Keyword(s):  
Graphene Layer ◽  
Peak Frequency ◽  
Epitaxial Graphene ◽  
Intensity Increase ◽  
Band Frequency ◽  
Graphene Layers ◽  
Exfoliated Graphene ◽  
Uv Raman Spectroscopy ◽  
Uv Raman ◽  
Deep Ultraviolet

We report microscopic Raman scattering studies of epitaxial graphene grown on SiC substrates using a deep-ultraviolet (UV) laser excitation at 266 nm to elucidate the interaction between the graphene layer and the substrate. The samples were grown on the Si-face of vicinal 6H-SiC (0001) substrates by sublimation of Si from SiC. The G band of the epitaxial graphene layer was clearly observed without any data manipulation. Increasing the number of graphene layers, the peak frequency of the G-band decreases linearly, while the peak width and the intensity increase. The G-band frequency of the graphene layers on SiC is higher than those of exfoliated graphene, which has been ascribed to compression from the substrate.

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.

Transparent Electrodes From Graphene/Single Wall Carbon Nanotube Composites

2013 ◽  
Author(s):  
Hossein Sojoudi ◽  
Fernando Reiter ◽  
Samuel Graham
Keyword(s):  
Electrical Properties ◽  
Sheet Resistance ◽  
Composite Films ◽  
Single Layer ◽  
Chemical Vapor ◽  
Optical Transmittance ◽  
Single Layer Graphene ◽  
Atmospheric Conditions ◽  
Transparent Conductive Electrode ◽  
Nanotube Composites

A transparent conductive electrode comprised of alternating layers of graphene grown by chemical vapor deposition (CVD) and metallic single wall nanotubes (M-SWNTs) is presented. It was found that the addition of two single-layer graphene sheets enhances the conduction pathways in the M-SWNT film, yielding up to a 75% decrease in the sheet resistance with little sacrifice in the optical transmittance. Enhancements in the electrical properties of the films were made through a heat treatment process followed by nitric acid and thionyl chloride doping, yielding a sheet resistance of 70 Ω/sq with a transmittance of 78% at 550 nm. Composite films having undergone an annealing step were found to have stable electrical properties upon exposure to atmospheric conditions while doped films demonstrated limited stability.

Graphene Growth by Transfer-Free CVD Method Using Cobalt/Nickel Catalyst Layer

2018 ◽  
Vol 919 ◽  
pp. 207-214
Author(s):  
Petr Machac ◽  
Ondrej Hejna
Keyword(s):  
Metal Layer ◽  
Chemical Vapour ◽  
Single Layer ◽  
Dielectric Substrate ◽  
Single Layer Graphene ◽  
Nickel Layer ◽  
Mechanical And Thermal Properties ◽  
Graphene Layers ◽  
Cvd Method ◽  
Cobalt Nickel

Graphene has been long considered for application in electronics manufacturing due to its extraordinary electronic, mechanical and thermal properties. This paper focuses on the graphene preparation onto dielectric substrate using transfer-free chemical vapour deposition (CVD) method with an intermediate catalytic metal layer (cobalt, nickel). Graphene layers were formed via segregation mechanism at temperatures in the range of 850 - 1050 °C onto the metal-dielectric boundary. Evaluated Raman spectra, which reveal the number of graphene layers and their defectivity suggested, that thinner metal layer and balanced ratio of H2:CH4 yield the best results for both cobalt and nickel layer. Spectra showed low amount of defects and the average number of carbon layers between 2-3, however, single-layer graphene (SLG) samples were also prepared. Scanning electron microscopy images showed that graphene domains on larger scale are not fully continuous.

scholarly journals Reduced crystallinity and enhanced charge transport by melt annealing of an organic semiconductor on single layer graphene

2016 ◽  
Vol 4 (19) ◽  
pp. 4143-4149 ◽  
Author(s):  
Vasyl Skrypnychuk ◽  
Nicolas Boulanger ◽  
Victor Yu ◽  
Michael Hilke ◽  
Michael F. Toney ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Charge Transport ◽  
Organic Semiconductor ◽  
Annealing Temperature ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Semiconducting Polymer ◽  
Layer Graphene ◽  
Melt Annealing

We report on the effect of the annealing temperature on the crystallization and the electrical properties of the semiconducting polymer poly(3-hexylthiophene) (P3HT) on single layer graphene.

Transport Properties of Single-Layer Epitaxial Graphene on 6H-SiC (0001)

2010 ◽  
Vol 645-648 ◽  
pp. 637-641 ◽  
Author(s):  
Johannes Jobst ◽  
Daniel Waldmann ◽  
Konstantin V. Emtsev ◽  
Thomas Seyller ◽  
Heiko B. Weber
Keyword(s):  
Quantum Hall ◽  
Single Layer ◽  
Intrinsic Property ◽  
Epitaxial Graphene ◽  
Electrical Measurements ◽  
Graphene Layers ◽  
Large Structures ◽  
Exfoliated Graphene ◽  
Shubnikov De Haas Oscillations ◽  
Van Der Pauw

We report on electrical measurements on epitaxial graphene on 6H-SiC (0001). The graphene layers were fabricated by thermal decomposition in Argon atmosphere. Large van der Pauw structures and Hall bars were patterned by e-beam lithography, the Hall bars ranged from rather large structures down to sub-micrometer sized Hall bars entirely placed on atomically °at substrate terraces. We present Hall measurements in a broad temperature range, Shubnikov de Haas oscillations and quantum Hall steps. The data lead to the conclusion that electrons in epitaxial graphene have the same quasi-relativistic properties previously shown in exfoliated graphene. A remarkable di®erence, however, is the stronger coupling to substrate phonons and the relatively high charging being an intrinsic property of this epitaxial system.

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.

Preparation of High-Quality Graphene by Sodium Borohydride Reducing Stage-1 FeCl3-GIC via In Situ Hydrogen Exfoliation

2017 ◽  
Vol 744 ◽  
pp. 458-462
Author(s):  
Xu Qiao ◽  
Zhi Lin ◽  
Yuan Yuan Si ◽  
Xiao Dan Lin ◽  
Shao Wei Cui ◽  
...  
Keyword(s):  
Sodium Borohydride ◽  
Single Layer ◽  
Single Layer Graphene ◽  
High Quality ◽  
Force Microscopy ◽  
Sem Image ◽  
Exfoliated Graphene ◽  
Atomic Force ◽  
Stage 1

High-quality graphene is prepared via In Situ hydrogen exfoliation of the reaction of stage-1 FeCl3-GIC with sodium borohydride solution, followed by washings and sonication. The hydrogen evolved from the borohydride exfoliates the GIC and reduces defect structure in the graphene simultaneously, make it more conjugated. Raman spectrum results show the intensity ratio of the D and G peak is about 0.09, even smaller than that of the original graphite, which is 0.17. The only C1s peak locating at 284.9 eV in another way supports the only one structure in the graphene. SEM image of exfoliated graphene Fig. 2(f) shows that the graphene obtained has curly morphology, which is significantly different from graphite flakes. TEM of the graphene shows a single layer graphene and its overlap with other graphene. Atomic force microscopy (AFM) measure shows that the average thickness of graphene sheets is about 0.530 nm. Proving that the high quality graphene prepared is chiefly single layer. After compression molded into graphene mat, its conductivity reaches 2.85×105S/m, which is about one third of the theoretical value of graphene. This method is promising for mass production of high-quality graphene.

Large and tunable thermoelectric effect in single layer graphene on bilayer graphene

2015 ◽  
Vol 29 (03) ◽  
pp. 1550003 ◽  
Author(s):  
Z. Z. Alisultanov
Keyword(s):  
Simple Model ◽  
Band Gap ◽  
Single Layer ◽  
Bilayer Graphene ◽  
Single Layer Graphene ◽  
Monolayer Graphene ◽  
Thermoelectric Effect ◽  
Layer Graphene ◽  
Trilayer Graphene

The conductivity and thermopower of a trilayer graphene based system have been studied within the framework of a simple model. It has been shown that kinks of the conductivity and peaks of the thermopower of the monolayer graphene formed on a tunable bilayer graphene appear near the edges of the band gap of the tunable bilayer graphene.

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