Growth of strained, but stable, graphene on Co

Amato, Giampiero; Beccaria, Federico; Celegato, Federica

doi:10.1016/j.tsf.2017.07.074

Cited by 6 publications

(35 citation statements)

References 39 publications

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“…According to Baraton et al, two distinct mechanisms can be considered for the graphene growth via C precipitation, the first at high temperature, which leads to large crystalline domains with low defect density, and the second at low temperature, which mainly provides nano‐crystalline graphene. Then, due to the higher heat of precipitation, graphene should grow on Co mainly by means of the first mechanism, typical of the higher T range, with enhanced coverage and encouraging electrical performances, as recently reported by Amato et al…”

Section: Introductionmentioning

confidence: 59%

“…In Amato et al, it is reported about full coverage of the graphene sheet, although the Co substrate presented nearly circular discontinuities resulting from dewetting. On film discontinuities, suspended graphene was observed, whose formation was ascribed to the rapid precipitation of C onto the Co surface in the first stages of the cooling process.…”

Section: Introductionmentioning

confidence: 98%

“…The most relevant difference on the growth mechanism of graphene on Co and Ni stems on the different heat of precipitation of C into the metal substrate, as highlighted in Amato et al Actually, Hasebe et al reported about a value for the heat of precipitation ∆ in Co about twice than in Ni at temperatures below its Curie temperature (T C = 1121°C), because of the magnetic contribution in the calculation of the enthalpy. Because the graphene growth is normally done around 1000°C, a temperature lower than T C (Co), but higher than T C (Ni), the thermally activated law describing the C solubility ( β )

β = β_{0} \cdot italicexp ([], \frac{- Δ}{k_{B} \cdot T})

holds for both metals (k B is the Boltzmann constant and T , the absolute temperature) but with activation energy Δ about twice in the Co case.…”

Section: Introductionmentioning

confidence: 99%

“…In that study, graphene deposition was carried out on Co thin films (500 nm thick) deposited on SiO 2 . Being the surface energy of the metal atoms at the grain boundaries unbalanced by the adhesion energy with the substrate, a valley is formed upon heating on the metal surface, which grows vertically and laterally.…”

Section: Introductionmentioning

confidence: 99%

“…Although the 2D line shape and the 2D/G intensity ratio provide a good measure of the number of layers in the case of exfoliated or Cu‐grown CVD graphene, departures from this situation have been reported for Ni‐grown and on Co‐grown CVD graphene and generally ascribed to spatial variations of the thickness of the graphene layer. Apart from such spatial inhomogeneities, there are other possible origins for the broadening/softening of the 2D mode, including optical effects, doping induced by the metal substrate, and strain, possibly originated by the different thermal expansion of graphene and its substrate.…”

Section: Introductionmentioning

confidence: 99%

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Raman analysis of strained graphene grown on dewetted cobalt

Amato

Beccaria

Landini

et al. 2019

J Raman Spectroscopy

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Graphene grows onto cobalt by means of diffusion of carbon atoms during the isothermal stage of exposure to hydrocarbon precursor, followed by precipitation during cooling. This method, largely applied with nickel catalyst, is known to produce continuous, but not uniform, layers with the concurrent presence of mono‐ and poly‐graphene areas. With the aid of Raman mapping of graphene still lying onto its catalyst, we are able to consider the possible origins for the observed distortions of the phonon modes with respect to the well‐known picture of the monolayer material. Optical effects, doping, the presence of multilayered islands, and strain are kept into account. It is shown that some observations can be interpreted in terms of the occurrence of isotropic strain with the uniaxial component superimposed at the metal discontinuities. Strain is proposed to originate from the difference between the thermal expansion coefficients of graphene and cobalt. The present paper shows that inhomogeneities in graphene grown onto catalysts with high C solubility are not always directly related to excess of precipitation. The observation of strain in as‐grown graphene opens the possibility of tailoring the electronic density of states via strain engineering directly during growth.

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Section: Introductionmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 98%

β = β_{0} \cdot italicexp ([], \frac{- Δ}{k_{B} \cdot T})

holds for both metals (k B is the Boltzmann constant and T , the absolute temperature) but with activation energy Δ about twice in the Co case.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Raman analysis of strained graphene grown on dewetted cobalt

Amato

Beccaria

Landini

et al. 2019

J Raman Spectroscopy

Self Cite

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Properties and applications of graphene membranes grown on Co

Amato

2020

Materials Today: Proceedings

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Production and processing of graphene and related materials

et al. 2020

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We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a ‘hands-on’ approach, providing practical details and procedures as derived from literature as well as from the authors’ experience, in order to enable the reader to reproduce the results. Section is devoted to ‘bottom up’ approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section covers ‘top down’ techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers’ and modified Hummers’ methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by ...

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Growth of strained, but stable, graphene on Co

Cited by 6 publications

References 39 publications

Raman analysis of strained graphene grown on dewetted cobalt

Raman analysis of strained graphene grown on dewetted cobalt

Properties and applications of graphene membranes grown on Co

Production and processing of graphene and related materials

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