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We theoretically and numerically investigate the growth of buckling-driven wrinkles in graphene monolayers. It is found that the growth of buckling-driven wrinkles in a graphene monolayer is remarkably chirality- and size-dependent. In small sizes, the flexural response of a graphene sheet cannot be accurately described by the classical Euler regime, and the non-continuum effect leads to zigzag-along-preferred buckling. With the increase of size, the width/length ratio α of the compressed region plays an important role in the growth of buckling-driven wrinkles. When α < 0.5, the oblique buckling happens in armchair-along compression; when 0.5 < α < 1.0, the effect of edge warp leads to zigzag-along-preferred buckling. When 1.0 < α < 3.0, the potential energy density difference due to chiral bending stiffness leads to armchair-along-preferred buckling. When α > 3.0, the non-continuum effect and chiral bending stiffness can both be neglected, and the buckling in a graphene monolayer is isotropic. The chirality-along-preferred transition of compressed buckling in a graphene monolayer leads to an improved fundamental understanding of the dynamics mechanism of graphene-based nanodevices, especially for the nanodevices with high frequency response. [ABSTRACT FROM AUTHOR]

The article presents a study by Kuang He and colleagues which describes the characteristics of graphene crystals from a mix of armchair, zigzag or reconstructed zigzag fragments resulting from two carbon atoms forming a pentagon with three neighbouring atoms of a zigzag edge.

We study the transmission characteristics of surface plasmons at the interface of a one-dimensional photonic crystal (1DPC) and a monolayer graphene sheet. The composite structure with a plasmonic band gap (PGB) was obtained by covering a graphene sheet on the lateral side of the 1DPC. Defect modes in these structures appeared when defect layers were inserted in the 1DPC. On the condition that the chemical potential of graphene is much larger than , the PBG and defect mode shift to higher frequencies as the chemical potential increases. As the carrier density in graphene can be controlled by the gate voltage, both the PBG and defect mode can be easily tuned by the chemical potential, which is determined by the carrier density. [ABSTRACT FROM AUTHOR]

We synthesize the homogenous graphene films on cheap industrial Cu foils using low pressure chemical vapor deposition. The quality and the number of layers of graphene are characterized by Raman spectra. Through carefully tuning the growth parameters, we find that the growth temperature, hydrocarbon concentration and the growth time can substantially affect the growth of high-quality graphene. Both single and bilayer large size homogenous graphenes have been synthesized in optimized growth conditions. The growth of graphene on Cu surface is found to be self ceasing in the bilayer graphene process with the low solubility of carbon in Cu. Furthermore, we have optimized the transfer process, and clear graphene films almost free from impurity are successfully transferred onto Si/SiO2 substrates. The field effect transistors of bilayer graphene are fabricated, which demonstrates a maximum hole (electron) mobility of 4300 cm2 V−1s−1 (1920 cm2V−1s−1) at room temperature. [ABSTRACT FROM AUTHOR]

A binder-free, high-rate Ge-three dimensional (3D) graphene composite was synthesized by directly depositing Ge film atop 3D graphene grown by microwave plasma chemical vapor deposition on Ni substrate. The Ge-3D graphene structure demonstrates excellent electrochemical performance as a lithium ion battery (LIB) anode with a reversible capacity of 1140 mAh g-1 at 1/3C over 100 cycles and 835 mAh g-1 at 8C after 60 cycles, and significantly a discharge capacity of 186 mAh g-1 was still achieved at 32C. The high capacity and outstanding stability of the Ge-3D graphene composite propose it as a promising electrode in high-performance thin film LIBs. [ABSTRACT FROM AUTHOR]

The temperature-dependent conductivity of bilayer graphene with adsorbed layers of the halocarbon molecule CF3Cl was studied under ultra high vacuum conditions. Upon warming CF3Cl sub-monolayer from 25 K, the electrical conductivity drops abruptly at 47 K and exhibits additional inflection points at 60 K and 69 K. CF3Cl multi-layers exhibit an abrupt conductivity gain at 54 K. These conductivity features correspond to known temperature-coverage phase boundaries for CF3Cl films measured on graphite. The changes in conductivity reflect changes in dielectric screening and disorder potential of the CF3Cl adlayer. The chemical specificity of phase transitions presents a basis for sensor selectivity. [ABSTRACT FROM AUTHOR]

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed in N-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes. The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study its application-feasibility in variable focus lens and various opto-electro-mechanical devices. [ABSTRACT FROM AUTHOR]

The structure of multi-wall carbon nanotubes has been attributed previously to disordered stacking of the graphene planes. Evidence is presented that the nanotubes analyzed in this paper occur with stacked graphene layers in the sequence of AA′, where alternate graphene planes are translated by half the hexagon width. We further present proof that the crystalline materials comprise graphene helices (∼5 nm in width), rather than in the form of a perfect tube. We also show that the structural model proposed here may be a common structure for multi-wall carbon nanotubes. [ABSTRACT FROM AUTHOR]

In this work, we propose a resonant tunnelling diode (RTD) based on a double-barrier graphene/boron nitride (BN) heterostructure as a device suitable to take advantage of the elaboration of atomic sheets containing different domains of BN and C phases within a hexagonal lattice. The device operation and performance are investigated by means of a self-consistent solution within the non-equilibrium Green's function formalism on a tight-binding Hamiltonian. This RTD exhibits a negative differential conductance effect, which involves the resonant tunnelling through both the electron and hole bound states in the graphene quantum well. It is shown that the peak-to-valley ratio reaches a value of ∼4 at room temperature even for zero bandgap and can be higher than 10 when a finite gap opens in the graphene channel. [ABSTRACT FROM AUTHOR]

There has been a long-standing dream to synthesize a semihydrogenated graphene sheet. Here, we propose a promising strategy based on physical method instead of chemical method to avoid the current problems in synthesizing. By applying pressure on a fluorinated BN sheet supported on a graphene sheet, we can induce a structural transition for H atoms jumping from the graphane sheet to fluorinated BN sheet, thus transforming the graphane sheet to a graphone sheet. Moreover, hole doping can reduce the pressure required for such structural transition. This strategy is more feasible and controllable as compared to the existing experimental techniques. [ABSTRACT FROM AUTHOR]