Strain Relaxation in CVD Graphene: Wrinkling with Shear Lag

Bronsgeest, Merijntje; Bendiab, Nedjma; Mathur, Shashank; Kimouche, Amina; Johnson, Harley T.; Coraux, Johann; Pochet, Pascal

doi:10.1021/acs.nanolett.5b01246

Cited by 77 publications

(69 citation statements)

References 59 publications

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“…In the position of wrinkles, the G band was a single Lorentz peak and the peak position showed a minimal (Figure b). Hence the strain was released in the vicinity of graphene wrinkles, consistent with the strain relaxation in CVD graphene grown on Co . In contrast, in the positions away from wrinkles, the G band split into G + and G − components, indicating the uniaxial (or nonequibiaxial) strain in graphene lattice (Figure b,c) .…”

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confidence: 67%

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces

Deng

Zhang

et al. 2018

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Corrugation is a ubiquitous phenomenon for graphene grown on metal substrates by chemical vapor deposition, which greatly affects the electrical, mechanical, and chemical properties. Recent years have witnessed great progress in controlled growth of large graphene single crystals; however, the issue of surface roughness is far from being addressed. Here, the corrugation at the interface of copper (Cu) and graphene, including Cu step bunches (CuSB) and graphene wrinkles, are investigated and ascribed to the anisotropic strain relaxation. It is found that the corrugation is strongly dependent on Cu crystallographic orientations, specifically, the packed density and anisotropic atomic configuration. Dense Cu step bunches are prone to form on loose packed faces due to the instability of surface dynamics. On an anisotropic Cu crystal surface, Cu step bunches and graphene wrinkles are formed in two perpendicular directions to release the anisotropic interfacial stress, as revealed by morphology imaging and vibrational analysis. Cu(111) is a suitable crystal face for growth of ultraflat graphene with roughness as low as 0.20 nm. It is believed the findings will contribute to clarifying the interplay between graphene and Cu crystal faces, and reducing surface roughness of graphene by engineering the crystallographic orientation of Cu substrates.

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confidence: 67%

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces

Deng

Zhang

et al. 2018

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“…If the reader is interested in the detection of graphene combined with the SERS effect, a further reading of the 2013 review can be found in the work of Xu et al [178]. A good way to differentiate between doping effect and subtract effect is to plot σ G versus σ 2D of the analyzed samples (this differentiation is possible because strain affects the band position by changing bond length and angles between bonds, whereas doping affects the electron-phonon coupling [179]). …”

Section: Graphenementioning

confidence: 99%

A Guide to and Review of the Use of Multiwavelength Raman Spectroscopy for Characterizing Defective Aromatic Carbon Solids: from Graphene to Amorphous Carbons

2017

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sp 2 hybridized carbons constitute a broad class of solid phases composed primarily of elemental carbon and can be either synthetic or naturally occurring. Some examples are graphite, chars, soot, graphene, carbon nanotubes, pyrolytic carbon, and diamond-like carbon. They vary from highly ordered to completely disordered solids and detailed knowledge of their internal structure and composition is of utmost importance for the scientific and engineering communities working with these materials. Multiwavelength Raman spectroscopy has proven to be a very powerful and non-destructive tool for the characterization of carbons containing both aromatic domains and defects and has been widely used since the 1980s. Depending on the material studied, some specific spectroscopic parameters (e.g., band position, full width at half maximum, relative intensity ratio between two bands) are used to characterize defects. This paper is addressed first to (but not limited to) the newcomer in the field, who needs to be guided due to the vast literature on the subject, in order to understand the physics at play when dealing with Raman spectroscopy of graphene-based solids. We also give historical aspects on the development of the Raman spectroscopy technique and on its application to sp 2 hybridized carbons, which are generally not presented in the literature. We review the way Raman spectroscopy is used for sp 2 based carbon samples containing defects. As graphene is the building block for all these materials, we try to bridge these two worlds by also reviewing the use of Raman spectroscopy in the characterization of graphene and nanographenes (e.g., nanotubes, nanoribbons, nanocones, bombarded graphene). Counterintuitively, because of the Dirac cones in the electronic structure of graphene, Raman spectra are driven by electronic properties: Phonons and electrons being coupled by the double resonance mechanism. This justifies the use of multiwavelength Raman spectroscopy to better characterize these materials. We conclude with the possible influence of both phonon confinement and curvature of aromatic planes on the shape of Raman spectra, and discuss samples to be studied in the future with some complementary technique (e.g., high resolution transmission electron microscopy) in order to disentangle the influence of structure and defects.

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“…Actually, the amplification of the Raman signals can be ascribed to interference effects, occurring for the structure graphene/air (500 nm)/SiO 2 (300 nm)/Si (see Figure c, I); here, the 500‐nm air layer takes the place of the 500‐nm Co film removed by dewetting. The optical path of the laser beam in the air layer is similar to the common graphene/SiO 2 (~300 nm)/Si assembly (see Figure c, II), whereas no interference occurs in the graphene/Co structure (see Figure c, III).…”

Section: Resultsmentioning

confidence: 99%

“…The optical path of the laser beam in the air layer is similar to the common graphene/SiO 2 (~300 nm)/Si assembly (see Figure c, II), whereas no interference occurs in the graphene/Co structure (see Figure c, III). The last effect, together with the screening from the metallic substrate, makes the collection of the Raman modes particularly inefficient when graphene lies onto Co …”

Section: Resultsmentioning

confidence: 99%

“…Actually, the amplification of the Raman signals can be ascribed to interference effects, [23][24][25] occurring for after cutting with a focused ion beam. The elliptical shape of the cutting, together with the disappearance of the corrugations orthogonal to the cut, proves that strain has relaxed the structure graphene/air (500 nm)/SiO 2 (300 nm)/Si (see Figure 2c, I); here, the 500-nm air layer takes the place of the 500-nm Co film removed by dewetting.…”

Section: Resultsmentioning

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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Strain Relaxation in CVD Graphene: Wrinkling with Shear Lag

Cited by 77 publications

References 59 publications

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces

A Guide to and Review of the Use of Multiwavelength Raman Spectroscopy for Characterizing Defective Aromatic Carbon Solids: from Graphene to Amorphous Carbons

Raman analysis of strained graphene grown on dewetted cobalt

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