Raman spectroscopy analysis of number of layers in mass-produced graphene flakes

Silva, Diego L.; Campos, João Luiz; Fernandes, Thales F. D.; Rocha, Jerônimo Nunes; Machado, Lucas Resende Pellegrinelli; Soares, Eder M.; Miquita, Douglas R.; Miranda, Hudson; Rabelo, Cassiano; Neto, Omar P. Vilela; Jório, Ado; Cançado, Luiz Gustavo

doi:10.1016/j.carbon.2020.01.050

Cited by 96 publications

(63 citation statements)

References 45 publications

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“…The analysis of the Raman bands showed a crystallite size (La) of 22nm and distance between point defects (Ld) of 10nm, which indicates a low amount of defects and a good quality graphene [26]. In addition the I2D/IG ratio [27] and the 2D band shape results can be interpreted, in accordance to recent studies as few-layer graphene [28]. The optical images in fig.…”

Section: Resultssupporting

confidence: 82%

Graphene Trails on PECVD Hydrogenated Amorphous Silicon Carbide Films SiC-a: H by Laser Writing at Room Temperature

Feria

Carreño

Rangel³

et al. 2020

JICS

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The production of high quality graphene without the need for catalyst metals as in the case of chemical vapor deposition (CVD) techniques remain a challenge. Silicon carbide is one of the materials with potential to form graphene films on its surface through thermal decomposition when subjected to high temperatures and ultrahigh vacuum. This technique is highly desirable since it enables the elimination of corrosion and transfer steps, which can leave residues in the graphene structure and alter its quality, as well as its electrical proprieties, however it is a costly and time consuming method. In this work, we present the production of graphene trails by direct laser radiation writing at room temperature and atmospheric pressure on hydrogenated amorphous silicon carbide films (SiC-a:H) produced by Plasma Enhanced Chemical Vapor Deposition (PECVD). Graphene trails of approximately 1cm x 4μm were obtained with patterns designed by computer Aided Design (CAD) software. Variations were made in both scanning speed and laser focal length, identifying a great dependence on the graphene quality with these two parameters. The best results of the Raman Spectroscopy Mappings showed high quality graphene with distance between point defects (LD) of 20nm, crystallite size (La) of 25nm and few layers (2-3). In addition, the electrical measurements from Au/Ti (20nm/100nm) electrodes deposited by electron beam evaporation showed high conductivity, with sheet resistances (Rs) from 0.7kΩ to 1.3 kΩ per square. This technique opens a great possibility of manufacturing devices for applications in electronics, being a fast, efficient and low cost method.

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Section: Resultssupporting

confidence: 82%

Graphene Trails on PECVD Hydrogenated Amorphous Silicon Carbide Films SiC-a: H by Laser Writing at Room Temperature

Feria

Carreño

Rangel³

et al. 2020

JICS

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“…Raman analysis results of graphene powder evaluated through a G‐protocol [43]. A, Lorentzian adjustment of the D, G, and D′ bands and, B, histogram with the distribution of the number of graphene layers [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Resultsmentioning

confidence: 99%

Hybrids nanocomposites based on a polymer blend (linear low‐density polyethylene/poly(ethylene‐co‐methyl acrylate) and carbonaceous fillers (graphene and carbon nanotube)

et al. 2020

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Interfacial or separate phase location of carbonaceous nanofillers (graphene and carbon nanotubes) in polymer blends with co‐continuous phases can lead to double percolation behavior, significantly increasing rheological and electrical properties. The prediction of the morphology and the location of the nanofillers has been used as a tool to evaluate the proprieties of co‐continuous polymer blends. This work aims to highlight the superior conductivity levels achieved using a low amount of carbon‐based fillers, by the proper selection in a multiphase polymer matrix as a template for controlled dispersion and spatial distribution of the nanoparticles, offering a compromise between easy processability and enhanced performance. Here, two polymers (linear low‐density polyethylene [LLDPE] and ethylene‐co‐methylacrylate [EMA]) and their co‐continuous blend (LLDPE/EMA) were loaded with nanofillers (few‐layer graphene [FLG], few‐walled carbon nanotube [FWCNT]) via continuous melt mixing in twin‐screw extrusion, separate and simultaneously. It was observed that the addition of the nanofillers changed the co‐continuity of the blend, with the probable migration of the nanofillers from the EMA (hydrophilic) phase to the LLDPE (hydrophobic) phase. Rheological percolation occurred preferentially in blends containing FWCNT and FLG/FWCNT. Electrical conductivity was observed in all compositions, with higher electrical conductivity being noticed in hybrids.

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“…Now, turbostratic graphite is by definition a three-dimensional graphite with no stacking order between adjacent layers (i.e., with a total lack of c-axis order), and that is the reason why it can be considered as a two-dimensional graphite to first approximation. By observing Figure 8a, in case of laser treatment, the single 2D peak evolves towards a two-peak (namely, 2D1 and 2D2) profile, as observed in graphitic samples formed by a large number (>5) of graphene layers [37], as well as in three-dimensional highly-ordered graphite [32]. Therefore, it can be inferred that fs-laser treatment is able to improve the stacking order of the graphitic phase of screen-printed carbon films.…”

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confidence: 73%

“…As can be seen from Figure 8a, the 2D band in the as-annealed untreated case can be fitted by a single Lorentzian centered at 2702.5 cm −1 and having a FWHM of about 70 cm −1 , which is the typical 2D band profile of two-dimensional graphite samples [35]. However, the presence of single-layer graphene, which returns a downshifted (in the range 2680-2690 cm −1 [36,37]) and narrower (20-30 cm −1 FWHM [36,38]) peak, should be excluded in our case, as already pointed out by the relationship I 2D /I G < 1. More likely, the single 2D peak in the as-annealed untreated case can be attributed to turbostratic graphite, which indeed shows a single 2D peak upshifted by about 20 cm −1 with respect to single-layer graphene, and with an almost double FWHM [34,36].…”

mentioning

confidence: 77%

Improving the Performance of Printable Carbon Electrodes by Femtosecond Laser Treatment

Girolami

Bellucci

Mastellone

et al. 2020

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Low-cost carbon-conductive films were screen-printed on a Plexiglas® substrate, and then, after a standard annealing procedure, subjected to femtosecond (fs) laser treatments at different values of total accumulated laser fluence ΦA. Four-point probe measurements showed that, if ΦA > 0.3 kJ/cm2, the sheet resistance of laser-treated films can be reduced down to about 15 Ω/sq, which is a value more than 20% lower than that measured on as-annealed untreated films. Furthermore, as pointed out by a comprehensive Raman spectroscopy analysis, it was found that sheet resistance decreases linearly with ΦA, due to a progressively higher degree of crystallinity and stacking order of the graphitic phase. Results therefore highlight that fs-laser treatment can be profitably used as an additional process for improving the performance of printable carbon electrodes, which have been recently proposed as a valid alternative to metal electrodes for stable and up-scalable perovskite solar cells.

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Raman spectroscopy analysis of number of layers in mass-produced graphene flakes

Cited by 96 publications

References 45 publications

Graphene Trails on PECVD Hydrogenated Amorphous Silicon Carbide Films SiC-a: H by Laser Writing at Room Temperature

Graphene Trails on PECVD Hydrogenated Amorphous Silicon Carbide Films SiC-a: H by Laser Writing at Room Temperature

Hybrids nanocomposites based on a polymer blend (linear low‐density polyethylene/poly(ethylene‐co‐methyl acrylate) and carbonaceous fillers (graphene and carbon nanotube)

Improving the Performance of Printable Carbon Electrodes by Femtosecond Laser Treatment

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