Ultrahard carbon film from epitaxial two-layer graphene

Gao, Yang; Cao, Tengfei; Cellini, Filippo; Berger, Claire; Heer, Walt de; Tosatti, Erio; Riedo, Elisa; Bongiorno, Angelo

doi:10.1038/s41565-017-0023-9

Cited by 204 publications

(217 citation statements)

References 40 publications

(82 reference statements)

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“…Notably, we obtain that the vertical distance from the exposed buffer layer to the nearby 1-layer region is approximately 1.2±0.3 nm, a value which accounts for the roughness of the buffer layer (≈ 0.3 nm) [41,48], the thickness of the newly formed graphene layer (1-layer, 0.34 nm) on top of BfL, and the thickness of the removed unit cell of 4H-SiC during sublimation (≈ 1 nm) [49]. comparable to the stiffness of freshly cleaved bare silicon carbide [10], since oxidation of external layers of SiC plays a role in reducing the mechanical stiffness of this substrate at the nanoscale after long exposition to air. Therefore, 1-layer epitaxial graphene exhibit stiffness at the nanoscale higher than the SiC substrate, as already discussed in our previous work [10,11], while we report herein that the same behavior is not observed in the 2-layer graphene film.…”

Section: Afm Morphology and Friction Map Of Epitaxial Graphene On Sicmentioning

confidence: 84%

“…The proposed mechanism for room-temperature formation of diamene from 1-layer plus BfL structures under pressure is a progressive re-hybridization of sp 2 2D layers into sp 3 diamene, which is an ultra-stiff and ultra-hard structure. The formation of the diamond-like diamene is favored by saturation at the BfL/substrate interface of the dangling bonds formed during the pressure induced rearrangement of atoms in the 1-layer/BfL layers [10].…”

Section: å-Indentation Of Epitaxial Graphene and Exfoliated Graphene mentioning

confidence: 99%

“…This technique is particularly effective in measuring elastic properties of 2D materials [22], thanks to indentation depths that are comparable to or smaller than the distance between the 2D layers (sub-Å). Å-indentation experiments have enabled direct measurement of the interlayer properties of epitaxial graphene and graphene oxide [22], as well as the discovery of the ultra-stiff diamene film on few-layers epitaxial graphene [10].…”

Section: å-Indentation For Transverse Elasticity Of 2d Layersmentioning

confidence: 99%

“…Recent research efforts have focused on the pressure induced formation of new phases in 2D materials. In particular, the formation of an ultrastiff phase, diamene, was found while locally pressurizing epitaxial graphene films [10,11]; other reports have shown the pressure induced formation of an insulating phase from exfoliated graphene flakes in a humid environment [12,13], and more recently the formation of bonitrol from hexagonal boron nitride was demonstrated [14].…”

Section: Introductionmentioning

confidence: 98%

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Layer dependence of graphene-diamene phase transition in epitaxial and exfoliated few-layer graphene using machine learning

Cellini¹,

Lavini²,

Berger³

et al. 2019

2D Mater.

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The study of the nanomechanics of graphene -and other 2D materials -has led to the discovery of exciting new properties in 2D crystals, such as their remarkable in-plane stiffness and out of plane flexibility, as well as their unique frictional and wear properties at the nanoscale.Recently, nanomechanics of graphene has generated renovated interest for new findings on the pressure-induced chemical transformation of a few-layer thick epitaxial graphene into a new ultrahard carbon phase, named diamene. In this work, by means of a machine learning technique, we provide a fast and efficient tool for identification of graphene domains (areas with a defined number of layers) in epitaxial and exfoliated films, by combining data from Atomic Force Microscopy (AFM) topography and friction force microscopy (FFM). Through the analysis of the number of graphene layers and detailed Å-indentation experiments, we demonstrate that the formation of ultra-stiff diamene is exclusively found in 1-layer plus buffer layer epitaxial graphene on silicon carbide (SiC) and that an ultra-stiff phase is not observed in neither thicker epitaxial graphene (2-layer or more) nor exfoliated graphene films of any thickness on silicon oxide (SiO2).

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Section: Afm Morphology and Friction Map Of Epitaxial Graphene On Sicmentioning

confidence: 84%

Section: å-Indentation Of Epitaxial Graphene and Exfoliated Graphene mentioning

confidence: 99%

Section: å-Indentation For Transverse Elasticity Of 2d Layersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

Layer dependence of graphene-diamene phase transition in epitaxial and exfoliated few-layer graphene using machine learning

Cellini¹,

Lavini²,

Berger³

et al. 2019

2D Mater.

Self Cite

View full text Add to dashboard Cite

show abstract

“…A configuration where graphene sheets present an interlayer distance lower than the stable equilibrium distance could be achieved by applying a fixed compression force normal to the stacked sheets. For example, experiments aiming to investigate the sliding motion between graphene sheets under metastable conditions as depicted in Figure 6d could be organized in the following steps: (1) generation of double layers of graphene (or graphene oxide), for instance by Langmuir-Blodgett assembly [41]; (2) compression of the double layers of graphene by means of a nano-indenter [42]; and (3) measurement of the forces occurring during the sliding dynamics by means of a nano-manipulator [26]. Note that characterization techniques such as atomic force microscopy (AFM) or in situ Raman mapping [43], as well as atomistic simulations [44,45], could support the experimental implementation and analysis of this system.…”

Section: Sheet-sheet Slidingmentioning

confidence: 99%

Sliding Dynamics of Parallel Graphene Sheets: Effect of Geometry and Van Der Waals Interactions on Nano-Spring Behavior

et al. 2018

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Graphene and carbon nanotubes are promising materials for nanoelectromechanical systems. Among other aspects, a proper understanding of the sliding dynamics of parallel graphene sheets or concentric nanotubes is of crucial importance for the design of nano-springs. Here, we analytically investigate the sliding dynamics between two parallel, rigid graphene sheets. In particular, the analysis focuses on configurations in which the distance between the sheets is kept constant and lower than the equilibrium interlayer spacing of graphite (unstable configurations). The aim is to understand how the interlayer force due to van der Waals interactions along the sliding direction changes with the geometrical characteristics of the configuration, namely size and interlayer spacing. Results show metastable equilibrium positions with completely faced sheets, namely a null force along the sliding direction, whereas net negative/positive forces arise when the sheets are approaching/leaving each other. This behavior resembles a molecular spring, being able to convert kinetic into potential energy (van der Waals potential), and viceversa. The amplitude of both storable energy and entrance/exit forces is found to be proportional to the sheet size, and inversely proportional to their interlayer spacing. This model could also be generalized to describe the behavior of configurations made of concentric carbon nanotubes, therefore allowing a rational design of some elements of carbon-based nanoelectromechanical systems.

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3D Graphene Foam Reinforced Low‐Temperature Ceramic with Multifunctional Mechanical, Electrical, and Thermal Properties

et al. 2019

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Graphene foam reinforced multifunctional ceramic composite is fabricated in this study. Graphene foam has a 3D macroporous architecture, which is filled with a low temperature co‐fired (LTCC) ceramic phase. The composite microstructure is engineered by three‐step fabrication scheme: infiltration of porous graphene foam with ceramic slurry, solidification to form a green body, and finally, pressure and temperature‐assisted sintering to produce a dense composite with intimate ceramic/graphene interface. Graphene foam is found to retain its 3D structure. The interconnected network of nodes and branches induces superior fracture toughness, load‐bearing capacity, and thermal − electrical transport characteristics. Addition of mere 0.18 wt% graphene foam results in a 480% improvement in the fracture energy. Sub‐surface examination reveals extensive crack deflection due to graphene foam's cellular units, highlighting the advantage of a 3D filler. Graphene foam also induces an impressive electrical conductivity of 165 S m−1 in an otherwise insulator ceramic. In situ infrared thermal imaging demonstrates enhanced thermal transportability in ceramic due to graphene foam. These findings attest the significance of 3D graphene foam to develop multifunctional ceramic composites in load‐bearing structures, thermal management, and electro‐mechanical devices. The synthesis scheme presented here is promising for facile and scalable manufacturing of this new class of materials.

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Ultrahard carbon film from epitaxial two-layer graphene

Cited by 204 publications

References 40 publications

Layer dependence of graphene-diamene phase transition in epitaxial and exfoliated few-layer graphene using machine learning

Layer dependence of graphene-diamene phase transition in epitaxial and exfoliated few-layer graphene using machine learning

Sliding Dynamics of Parallel Graphene Sheets: Effect of Geometry and Van Der Waals Interactions on Nano-Spring Behavior

3D Graphene Foam Reinforced Low‐Temperature Ceramic with Multifunctional Mechanical, Electrical, and Thermal Properties

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