We present the experimental evidence of RF demodulation by a graphene monolayer embedded in a coplanar structure. The demodulator was tested in the frequency range from 100 MHz to 25 GHz using amplitude modulated input signals. An input power of 0 dBm (1 mW) was used which is the typical power emitted for short range wireless communication systems, such as Bluetooth. The graphene demodulator exhibits good signal response in the frequency range associated to industrial, scientific and medical (ISM) radio band (2.4 GHz).
A thermal transport mechanism leading to the enhanced thermal conductivity of Graphene nanofluids has been proposed. The Graphene sheet size is postulated to be the key to the underlying mechanism. Based on a critical sheet size derived from Stokes-Einstein equation for the poly-dispersed nanofluid, sheet percolation and Brownian motion assisted sheet collisions are used to explain the heat conduction. A collision dependant dynamic conductivity considering Debye approximated volumetric specific heat due to phonon transport in Graphene has been incorporated. The model has been found to be in go…
We study the discrete energy spectrum of curved graphene sheets in the presence of a magnetic field. The shifting of the Landau levels is determined for complex and realistic geometries of curved graphene sheets. The energy levels follow a similar square root dependence on the energy quantum number as for rippled and flat graphene sheets. The Landau levels are shifted towards lower energies proportionally to the average deformation and the effect is larger compared to a simple uni-axially rippled geometry. Furthermore, the resistivity of wrinkled graphene sheets is calculated for different ave…
Large-scale atomically thin metals can be stabilized through confinement epitaxy at graphene / SiC interface, which exhibit a gradient bonding type and are air stable, providing a compelling platform for quantum and optoelectronic technologies.
Considerable efforts have been made to trap massless Dirac fermions in graphene monolayer, but only quasi-bound states are realized in continuous graphene sheets up to now. Here, we demonstrate the realization of bound states in nanoscale graphene quantum dots (GQDs) in a continuous graphene sheet. The GQDs are electronically isolated from the surrounding continuous graphene sheet by circular boundaries, which are generated by strong coupling between graphene and substrate. By using scanning tunneling microscopy (STM), we observe single-electron charging states of the GQDs, seen as Coulomb osc…
We present a study of the wrinkling modes, localized in the plane of single- and few-layer graphene sheets embedded in or placed on a compliant compressively strained matrix. We provide the analytical model based on nonlinear elasticity of the graphene sheet, which shows that the compressive surface stress results in spatial localization of the extended sinusoidal wrinkling mode with soliton-like envelope with localization length, decreasing with the overcritical external strain. The parameters of the extended sinusoidal wrinkling modes are found from the conditions of anomalous softening of f…
Organic ferroelectric layers sandwiched between the graphene sheets are presented as a model of the solar cell. The investigated systems display many advantageous properties: 1) the cascade energy-levels alignment, 2) simultaneous donor and acceptor character depending on the charge-carrier direction, 3) the charge-transfer excitonic type, 4) the induced polarization of the electrodes, leading to a substantial work-function change of the anode and cathode - around +/-1.5 eV, respectively.
The orbital magnetic susceptibility (OMS) of a gas of noninteracting massless Dirac fermions is zero when the Fermi energy is away from the Dirac point. Making use of diagrammatic perturbation theory, we calculate exactly the OMS of massless Dirac fermions to first order in the Coulomb interaction demonstrating that it is finite and positive. Doped graphene sheets are thus unique systems in which the OMS is completely controlled by many-body effects.
We study the dependence of mechanical conformations of graphene sheets located on flat substrates on the density of unilateral (one-side) attachment of hydrogen, fluorine or chlorine atoms to them. It is shown that chemically modified graphene sheet can take four main forms on a flat substrate: the form of a flat sheet located parallel to the surface of the substrate, the form of convex sheet partially detached from the substrate with bent edges adjacent to the substrate, and the forms of single and double rolls on the substrate. On the surface of crystalline graphite, the flat form of the she…
Epitaxial graphene grown on SiC by the confinement controlled sublimation method is reviewed, with an emphasis on multilayer and monolayer epitaxial graphene on the carbon face of 4H-SiC and on directed and selectively grown structures under growth-arresting or growth-enhancing masks. Recent developments in the growth of templated graphene nanostructures are also presented, as exemplified by tens of micron long very well confined and isolated 20-40nm wide graphene ribbons. Scheme for large scale integration of ribbon arrays with Si wafer is also presented.
We study the effect of disordered ripples on the conductivity of monolayer graphene flakes. We calculate the relaxation times and the Boltzmann conductivities associated with two mechanisms. First, we study the conductivity correction due to an external in-plane magnetic field $B_\parallel$. Due to the irregular local curvature found at graphene sheets deposited over a substrate, $B_\parallel$ can be mapped into an effective random magnetic field perpendicular to the graphene surface. Second, we study the electron momentum relaxation due to intrinsic pseudo magnetic fields originated from defo…
This erratum aims to correct 1) the wrong expressions, 2) some typographical errors, 3) some erroneous points made in discussion of the disparity of heat flux ratios between our full RPA model and the local conductivity model, and 4) the lower bound of the characteristic distance scale comparable to the graphene thermal length, appearing in the original paper, which might confuse or mislead readers. Collectively, they don't change the key physics we sought to present.
Constrained density functional theory (CDFT) is used to evaluate the energy level alignment of a benzene molecule as it approaches a graphene sheet. Within CDFT the problem is conveniently mapped onto evaluating total energy differences between different charge-separated states, and it does not consist in determining a quasi-particle spectrum. We demonstrate that the simple local density approximation provides a good description of the level aligmnent along the entire binding curve, with excellent agreement to experiments at an infinite separation and to GW calculations close to the bonding di…
We derive an integral equation describing surface-plasmon polaritons in graphene deposited on a substrate with a planar surface and a dielectric protrusion in the opposite surface of the dielectric slab. We show that the problem is mathematically equivalent to the solution of a Fredholm equation, which we solve exactly. In addition, we show that the dispersion relation of the localized surface plasmons is determined by the geometric parameters of the protrusion alone. We also show that such system supports both even and odd modes. We give the electrostatic potential and the stream plot of the …
In this chapter, semi-analytical models for the calculation of the quantum capacitance of both monolayer and bilayer graphene and its nanoribbons, are presented. Since electron-hole puddles are experimental facts in all graphene samples, they have been incorporated in our calculations. The temperature dependence of the quantum capacitance around the charge neutrality point is also investigated and the obtained results are in agreement with many features recently observed in quantum capacitance measurements on both monolayer and bilayer graphene devices. Furtheremore, the impact of finite-size …
Phononic (thermal) devices are studied such as thermal diode, thermal transistors, thermal logic gates, and thermal memories. However, the thermal resistor has not been demonstrated yet. Here, we propose an instantaneously adjustable thermal resistor by folded graphene. Through theoretical analysis and molecular dynamics simulations, we studied the phonon folding effect and the dependent of thermal resistivity on the length between two folds and the overall length. Further, we discuss on the possibility to realize the instantaneously adjustable thermal resistor in experiment. Our studies bring…
The stationary Josephson current in a ballistic graphene system is theoretically studied with focus on a planar junction consisting of a monolayer graphene sheet on top of which a pair of superconducting electrodes is deposited. To characterize such a planar junction, we employ two parameters: the coupling strength between the graphene sheet and the superconducting electrodes, and a potential drop induced in the graphene sheet by direct contact with the electrodes. We derive a general formula for the Josephson current by taking these parameters into account in addition to other basic parameter…
It is shown using the method of molecular dynamics that the motion of carbon nanoparticles (rectangular graphene flakes, spherical fullerenes of size $L<10$ nm) on the surface of a thermalized graphene sheet lying on a flat substrate can be described as the motion of particles in a viscous medium with a constant coefficient of friction, the value of which depends on the temperature and particle size. It has been shown that there are two types of effective friction: diffusion and ballistic. In ballistic regime of motion (at velocities $v>100$ m/s), deceleration occurs due to the interaction of …
We propose a device in which a sheet of graphene is coupled to a Weyl semimetal, allowing for the physical access to the study of tunneling from two-dimensional to three dimensional massless Dirac fermions. Due to the reconstructed band structure, we find that this device acts as a robust valley filter for electrons in the graphene sheet. We show that, by appropriate alignment, the Weyl semimetal draws away current in one of the two graphene valleys while allowing current in the other to pass unimpeded. In contrast to other proposed valley filters, the mechanism of our proposed device occurs i…
In this work the Casimir{Polder interaction energy between a rubidium atom and a disordered graphene sheet is investigated beyond the Dirac cone approximation by means of accurate real-space calculations. As a model of defected graphene, we consider a tight-binding model of Π-electrons on a honeycomb lattice with a small concentration of point defects. The optical response of the graphene sheet is evaluated with full spectral resolution by means of exact Chebyshev polynomial expansions of the Kubo formula in large lattices with in excess of ten million atoms. At low temperatures, the optical r…
