Heat removal became crucial issue for continuing progress in electronic, optoelectronic and photonic industries. Carbon allotropes and derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials spans an extraordinary large range from the lowest in amorphous carbons to the highest in graphene. I review thermal properties of graphene, discuss distinctions between intrinsic and extrinsic thermal conductivity and describe prospects of graphene applications for thermal management in electronics and optoelectronics.ý

We report about scanning Raman experiments on, both, as deposited and nano-structured graphene flakes. The Raman scans allow us to extract spatially resolved information about frequencies, intensities and linewidths of the observed phonon modes. In nano-structured single-layer flakes, where periodic arrays of holes (antidots) were fabricated by electron-beam lithography and subsequent etching, we find a systematic dependence of the phonon frequencies, intensities and linewidths on the periods and hole sizes of the nano-patterned regions. A systematic shift of the G mode frequency evidences a doping effect in the nano-patterned regions. In order to calibrate the doping dependence of the G mode phonon frequency, we have investigated the position and linewidth of this mode in a gated single-layer flake. With this calibration, we can quantitatively determine the doping level, which is introduced via preparation of the periodic hole arrays into the samples. A comparison of G and 2D mode frequencies allows us to identify the doping to be of p-type.

This contribution deals with Carbon Nanotubes Field Effect transistors (CNTFETs) based gas sensors fabricated using a new dynamic spray based technique for SWCNTs deposition. This technique is compatible with large surfaces, flexible substrates and allows to fabricate high performances transistors exploiting the percolation effect of the SWCNTs networks achieved with extremely reproducible characteristics. Recently, we have been able to achieve extremely selective measurement of NO₂ , NH₃ and DMMP using four CNTFETS fabricated using different metals as electrodes (Pt, Au, Ti, Pd), exploiting the specific interaction between gas and metal/SWCNT junction. In this way we have identify a sort of electronic fingerprinting of the gas. The time response is evaluated at less than 30sec and the sensitivity can reach 20ppb for NO₂, 100ppb for NH₃ and 1ppm for DMMP (Di-Methyl-Methyl-Phosphonate).

We report an all-printed flexible carbon nanotube (CNT) thin-film transistor (TFT). All the CNT TFT components, including the source and drain electrodes, the TFT transport channel, and the gate electrode, are printed on a flexible substrate at room temperature. A high ON/OFF ratio of over 10³ was achieved. The all printed CNT-TFT also exhibits bias-invariant transconductance over a certain gate bias range. This all-printed process avoids the conventional procedures in lithography, vacuum, and metallization, and offers a promising technology for low-cost, high-throughput fabrication of large-area flexible electronics on a variety of substrates, including glass, Si, indium tin oxide and plastics.

Photochromic materials reversibly change their colour due to a photochemical reaction that takes place when the material is irradiated with photons of suitable energy. This peculiar feature has been extensively exploited to develop smart sunglasses, filters and inks. With a proper molecular design it is possible to enable modulation not only of colour but also of other properties such as refractive index, dipole moment, nonlinear optical properties or conductivity by a photoswitching of the molecular structure. The approach herein developed consists in modifying, upon irradiation, the properties of a molecular component coupled with the photochromic molecule. In particular, the switching features of photochromic systems are matched with the intriguing peculiar properties of carbon nanotubes (CNTs). A photochromic polyester has been properly synthesised to be used as switching polymer matrix coupled with a network of CNTs. Irradiation of the polymer/CNTs blend results into a light-triggered conductance switching. The reversible electrocyclization of the polymer under UV-vis illumination results into a modification of the inter-tube charge mobility, and accordingly, of the overall resistance of the blend. Solution techniques allow us to obtain blended films with sheet resistance modulation larger than 150%, good thermal stability and fatigue resistance at room conditions, in an easier, faster and scalable way as respect to the single-molecule approach.ÿ

In this paper, we report on the optical and electrical properties of single-walled (SWNT) and multi-walled (MWNT) carbon nanotube thin-films investigated by terahertz time-domain spectroscopy. Our study focuses on the absorption and dispersion properties of the single-walled and multi-walled carbon nanotubes in frequency range of 0.1-2 THz. The results show that the single-walled carbon nanotubes thin-films have the great frequency-dependent of the power absorption coefficient, the index of the refraction and conductivity compared to the multi-walled carbon nanotubes thinfilms because more mobile carries of carbon nano-structure as well as effective of carbon nanotubes length and diameter.

Data communications have been growing at a speed even faster than Moore's Law, with a 44-fold increase expected within the next 10 years. Data Transfer on such scale would have to recruit optical communication technology and inspire new designs of light sources, modulators, and photodetectors. An ideal optical modulator will require high modulation speed, small device footprint and large operating bandwidth. Silicon modulators based on free carrier plasma dispersion effect and compound semiconductors utilizing direct bandgap transition have seen rapid improvement over the past decade. One of the key limitations for using silicon as modulator material is its weak refractive index change, which limits the footprint of silicon Mach-Zehnder interferometer modulators to millimeters. Other approaches such as silicon microring modulators reduce the operation wavelength range to around 100 pm and are highly sensitive to typical fabrication tolerances and temperature fluctuations. Growing large, high quality wafers of compound semiconductors, and integrating them on silicon or other substrates is expensive, which also restricts their commercialization. In this work, we demonstrate that graphene can be used as the active media for electroabsorption modulators. By tuning the Fermi energy level of the graphene layer, we induced changes in the absorption coefficient of graphene at communication wavelength and achieve a modulation depth above 3 dB. This integrated device also has the potential of working at high speed.

Although graphene has fascinating electronic properties, lack of a band-gap reduces its utility for conventional electronic device applications. A tunable bandgap can be induced in bilayer graphene by application of a potential difference between the two layers. The simplest geometry for creating such a potential difference consists of two overlapping single layer graphene nanoribbons. Numerical simulations, based on π-band nearest neighbor tight binding model and the nonequilibrium Green's function formalism, show that transmission through such a structure has a strong dependence on applied bias. The simulated current voltage characteristics mimic the characteristics of resonant tunneling diode featuring negative differential resistance. It is found that the bandgap of the nanoribbons and length of the bilayer region have significant effects on the current voltage characteristics. In particular, the peak to valley ratio decreases with increasing length of the bilayer region. And the cut-in voltage is strongly modulated by the bandgap of the GNRs.

In this work, phonon dispersion relation of trilayer graphene with ABA stacking has been calculated by using forceconstant model. In our calculation we have considered fifth nearest neighbors in plane of graphene and the interaction between the nearest layers. By using the calculated phonon dispersion relation, phonon thermal conductivity of trilayer graphene is investigated by Landaur theory at low temperatures. In force constant model, atoms are considered as a point masses that move according to the classical mechanics laws. By formation of dynamical matrix and solving the secular equation detD(k)=0 the eigen frequencies can be achieved. It can be seen that the degeneracy of the lowest acoustic branch is splited into the three branches near the Briloan zone for trilayer graphene, which is due to weak van der waals interaction between two layers. In addition, the phonon thermal conductivity increases by raising the number of layers.

Recently, one of the most significant topics in electronic devices is miniaturization. It has been a growing interest in some mesoscopic systems such as quantum dots. The size of these quantum dots approaches to the atomic scale, which contributes to interesting new behaviors. Understanding their properties is an important problem in the fields of nano electronics. Here we study the transport properties of the single wall carbon nanotubes quantum dots. Considering Carbon nanotube (2n,0)/1(n,n)/m(2n,0) quantum dot, we have investigated the effects of the central cell size on the conductance of the system. By increasing the length of armchair carbon nanotube in metalmetal- metal quantum dot m(12,0)/1(6,6)/m(12,0) , we have observed reduction in the conductance. In semiconductor- metal- semiconductor quantum dots (8,0)/1(4,4)/m(8,0), increasing the length of armchair part causes the scattering rate raising. For more than special length, due to the destructive and constructive interference of the wave functions, the conductance gap oscillates near the Fermi energy. Therefore, by controlling on cell size characteristics, it is possible to manipulate some efficient devices in nano-electronics.

Graphene has recently attracted many attentions for some special properties. One of the most important advantages of graphene is its very high electron mobility, which is essential to manipulate high-speed next generation transistors and other nano-electronic devices. Besides, because of the thin layer of carbon atoms in graphene, we can make ultra-small and extremely fast devices. In this research, we have considered a monolayer graphene subjected to an electro-magneto static field. By solving the Dirac equation analytically and finding the spin-dependent transmission probability for electrons through the barrier constructed by the electro-magneto static field, we have evaluated spin polarization in different conditions. Our results show there is no reduction in transmission for electrons that vertically go through the barrier. In other words, we have unit transmission probability at normal incidence, which is in complete accord with Klein paradox. In this case, there is not any polarization. However, spin polarization can be seen by increasing the incident angle. In some special magnetic field strengths and incident angels, spin-filtering can be occurred, in which only electrons with either spin-up or spin-down can pass through the barrier. Due to this fact, many graphene-base spintronic devices can be exploited in the near future.

Mechanical deformations cause to change the electronic properties in carbon nanotubes. In this paper, the uniaxial strain and length effects have been investigated on the quantum conductance of (12,0) and (8,0) finite Zigzag Single Wall Carbon Nanotubes (ZSWCNT) at Fermi energy, using the tight binding model and the Green's function technique. In the absence of strain, all the finite ZSWCNTs are metal because of localization. Our probes show that by controlling the uniaxial strain and carbon nanotube length, a metal-semiconductor transition occurs for (8,0) finite ZSWCNT under the compressive strain condition and the length longer than 37 A⁰. However, under the all strain and length variations that investigated conditions in this paper, the localization length is longer than the length of (12,0) finite ZSWCNT, so that it remains metallic and the quantum conductance is non-zero. Some exciting applications of the correspondence between the mechanical response and the electronic transport of the carbon nanotubes are nano-electromechanical switch, sensor applications.