Graphene has been one of the hottest topics in materials science in the last years. Because of its special electronic properties graphene is considered one of the most promising materials for future electronics. However, in its pristine form graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Many approaches have been tried to create, in a controlled way, a gap in graphene. These approaches have obtained limited successes. Recently, hydrogenated graphene-like structures, the so-called porous graphene, have been synthesized. In this work we show, based on ab initio quantum molecular dynamics calculations, that porous graphene dehydrogenation can lead to a spontaneous formation of a nonzero gap two-dimensional carbon allotrope, called biphenylene carbon (BC). Besides exhibiting an intrinsic nonzero gap value, BC also presents well delocalized frontier orbitals, suggestive of a structure with high electronic mobility. Possible synthetic routes to obtain BC from porous graphene are addressed.

A combined experimental and simulation approach into the impacts of electron irradiation on carbon nanotube morphology was conducted. Single-walled nanotubes (SWCNTs) were irradiated using a JEOL Transmission Electron Microscope (TEM) using a range of accelerating voltages varying from 90keV to 200keV and temperatures between 300K and 800K with different exposure periods (order of minutes). The effects of irradiation were observed and characterised using electron microscopy and Raman spectroscopy. Specimens were observed prior to, during and following irradiation to discern any changes that occurred in SWCNTs as a result of irradiation. Raman spectroscopy was used to characterise the different allotropes of carbon present in irradiated and non-irradiated samples of SWCNTs. Experimental conditions were mimicked using molecular dynamics simulation. SWCNTs were irradiated under conditions equivalent to experimental electron beam intensity and specimen temperature using AIREBO [1,2] and Primary Knock-on (PKA) approximation [3]. The preliminary results indicate that electron beam intensity and temperature affect the type and frequency of modification to CNT structure.

Exchange of solubilizers adsorbed on single-walled carbon nanotubes (CNTs) is probed by analysis of the peak shifts of the absorption bands of CNTs in the near-infrared region. Equilibrium constants and thermodynamic parameters of the exchange of sodium cholate for DNA (15-mers of oligo-DNAs, cytosine) on CNTs of different chirality are determined.

A new type of cathode for electron field emission (FE) was fabricated. The cathode was made from ultra-thin multiwalled carbon nanotube (CNT) sheets. These sheets were drawn directly from a CNT forest, stacked layer-by-layer together and densified by isopropyl alcohol. CNT emitters were formed by utilizing laser beam to cut the sheet. The FE performance of the proposed devices has been enhanced dramatically. The threshold field for electron emission (at which the emission current is 10 mA/cm2) was 0.88 V/μm. The current density of 36 A/cm2 was achieved at the electric field of 2 V/μm. The enhanced performance is the result of the thin, uniformly distributed and aligned array of the CNT emitters.

The temperature dependent resistance R(T) and thermopower S(T) of sintered single wall carbon nanotubes (SWCNT) and magnesium diboride (MgB2) composites containing 5wt%, 10wt%, and 15wt% of SWCNTs have been measured and compared to their pure counterparts. The thermopower of both MgB2 (in the normal state) and SWCNT remain positive over the entire temperature range (10K to 300K) with room temperature values being ∼ 8μV/K and 57μV/K, respectively. The thermopower of the sintered composites decreased with decreasing temperature and switched from positive to negative near 70K. The superconducting critical temperature (Tc) of the samples ranges from 38K-41K. The room-temperature resistance ratio (RRR) is seen to depend on the sample composition. The temperature width (ΔT) is observed to increase with increasing SWCNT concentration. The normal state resistance data were fitted with the generalized Block-Grüneisen function obtaining Debye temperature of ∼ 900K.

Our works have been concentred on the characterization of single wall carbon nanotube (SWCNT) composites films in order to obtain a new easy processing anode for organic device. The morphology and charge transport in poly(3,4-ethylenedioxythiophene) poly (4-styrenesulfonate) / SWCNT thin layers was investigated. PEDOT:PSS polymer acts as host material and an excellent dispersion of metallic single wall carbon nanotube (m-SWCNT) can be achieved enhancing the polymer’s electrical properties. The PEDOT:PSS/SWCNT films are prepared on glass substrates using spin coating method. Raman spectroscopy has been used to observe the surface states of PEDOT: PSS/SWCNT films and to realize Raman mapping that allow determining the homogeneity of the SWCNT dispersion into the films. Optical and electrical characterizations (sheet resistance, conductivity) of the films are also presented.

We report a technique that can, in principle, selectively convert SiC into graphene at any location and in any size or shape, limited only by the ability of the available lithographic techniques. This technique relies on our discovery that, at ambient condition, a laser beam can convert SiC into graphene layers at the illuminated site, and the conversion can be realized in two ways. One can pattern the SiC film, which is already grown on a Si wafer, with desirable features and then illuminate the SiC film with the laser, or simply “write” the graphene features directly onto the unpatterned SiC film with the laser. Alternatively, one can pre-pattern the Si substrate to achieve selective growth of SiC, then perform the laser conversion. We have demonstrated the feasibility of both approaches. Fullerene (C60) was used to grow a thin SiC film on a Si (111) substrate using molecular beam epitaxy (MBE) at 700-800 oC. The results are verified by various structural, chemical and optical characterization techniques. This work yields the possibility of fabricating graphene based (electronic) nanostructures or superlattices, photonic crystals, and integrated electronic and optoelectronic devices on a large Si wafer.

Graphene-based materials have emerged as exceptional candidates for the development of novel, high performance actuators. Developing such an actuation material requires an in depth knowledge of the physics of operation and, therefrom, how to best optimize its performance. We investigate the electromechanical actuation of pristine monolayer graphene to elucidate the origin of this material’s exceptional electromechanical actuation performance. It is shown that the electrostatic double-layer (EDL) effect is dominant compared to the quantum-mechanical (QM) effect upon charging and electrolyte immersion. Seeking to optimize the QM actuation performance, we preliminarily investigate graphene oxide (GO) as a potential graphene-based actuation material, and find that it exhibits both unique and high performance responses. Having demonstrated huge stresses (~100 GPa) and high strains (~0.4%), graphene-based materials are uniquely positioned to address future industrial actuation challenges.

The discovery of carbon nanotubes and subsequently graphene has led to an interest in carbon materials as sensing elements due to their unique properties. Graphene is a 2-dimensional material that has a large surface area (~2630 m2g-1) that can be exposed to surface adsorbates from a target gas. This enables studies on the interaction of gas molecules with the graphene surface and resulting changes in its properties, making graphene an excellent sensing element. We present our graphene based sensor with the focus on designing small, cost effective and reliable sensors with high sensitivity towards the target gas, detailing the assembly of graphene/acrylic based devices, their characterization and investigation of their performance as resistive chemical sensors

Using advanced first-principles calculations, we have studied the structural and electronic properties of graphene/α-Al2O3 interfaces and show that α -Al2O3 is an ideal gate dielectric material for graphene transistors. Clean interface exists between graphene and Al-terminated (or hydroxylated) Al2O3 and the valence band offsets for these systems are large enough to create injection barrier. Remarkably, a band gap of ~180 meV can be induced in graphene layer adsorbed on Al-terminated surface, which is significantly larger than graphene on other popular substrates.

In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data.

The morphology of graphene on Si and SiC substrates is investigated using molecular- dynamics simulation. The effects of the size and orientation of graphene on its roughness, distance from the substrate, and periodic structure are examined. The roughness and distance show the size dependency which agrees with the size dependency of the ratio of the periphery length of graphene to its area. It is found there are some cases in which the roughness of graphene can be suppressed.

We have investigated the hexagonal graphene network (GNW) structure for the possible opening of the graphene bandgap. We have fabricated GNW by nanoimprint lithography and compared with previous GNW results based on electron beam (EB) lithography. Hall-bar device with GNW was successfully fabricated using nanoimprint lithography and verified mobility of 1,220 cm2 V-1 s-1 with graphene nanoribbon (GNR) width of 40 nm. The mobility improvement compared with GNW by EB lithography indicates the effectiveness of nanoimprint method for the hexagonal GNW approach.

We report the fabrication and characterisation of the first graphene ring micro electrodes, formed by dip coating fibre optics with subsequently reduced graphite oxide. The behaviour of the so-formed Graphene RIng Micro Electrodes (GRIMEs) is studied using the ferricyanide probe redox system while electrode thicknesses is assessed using established electrochemical methods. A ring electrode of ∼73 nm thickness is produced on 220 μm diameter fibre optics, corresponding to an inner to outer radius ratio of >0.999, so allowing for use of extant analytical descriptions of very thin ring micro electrodes in data analysis. GRIMEs are highly reliable (current response invariant over >3000 scans) with the microring design allowing for efficient use of electrochemically active graphene edge sites. Further, the associated nA scale currents neatly obviate issues relating to the high resistivity of undoped graphene. Thus, the use of graphene in ring micro electrodes improves the reliability of existing micro electrode designs and expands the range of use of graphene-based electrochemical devices.

The equilibrium geometry and electronic structure of graphene deposited on a multilayer hexagonal boron nitride (h-BN) substrate has been investigated using the density functional and pseudopotential theories. We found that the energy band gap for the interface between a monolayer graphene (MLG) and a monolayer BN (MLBN) lies between 47 and 62 meV, depending on the relative orientations of the layers. In the most energetically stable configuration the binding energy is found to be approximately 40 meV per C atom. Slightly away from the Dirac point, the dispersion curve is linear, with the electron speed almost identical to that for isolated graphene. The dispersion relation becomes reasonably quadratic for the interface between MLG and 4-layer-BN, with a relative effective mass of 0.0047. While the MLG/MLBN superlattice is metallic, the thinnest armchair nanoribbon of MLG/MLBN interface is semiconducting with a gap of 1.84 eV.

Graphene, a two-dimensional carbon allotrope, has raised great interests as a material candidate for future electronics due to its superb carrier transport and unique physics. The demand for future-generation large-scale carbon-based electronics motivates assembly of large-area graphene and selection of ideal substrate material that best preserves the transport property of graphene. In this work, CVD-assembled large-area graphene on thin multilayer hexagonal boron nitride (h-BN) is employed to demonstrate the basic building block of digital circuit - inverter prototype made of two graphene-channel field-effect transistors (GFETs). The doping in the CVD-grown graphene, probed via electrical measurements, is implemented through non-uniform local surface chemistry. The full transfer response of the graphene logic inverter is demonstrated in the localized P/N doping region.

This study presents a materials development of composite electrode materials of graphene oxide (GO) and transition metal oxide nanostructures. Reduced graphene oxide (rGO) films were obtained by electrophoretic deposition (EPD) onto a conductive substrate. Co3O4 and MnO2 nanostructures were synthesized to form composites with rGO. Graphene materials, with high electrical conductivity, high specific surface area and excellent mechanical properties are ideal for a host of electrical applications. The properties of metal oxides like Co3O4 and MnO2 has allowed for increased energy density, while rGO increases charge storage and transport in the electrical double layer at the electrode/electrolyte interface. Graphene and metal oxide composites offer increased energy density and capacitance compared with traditional double layer supercapacitors.

The interactions of fully stripped Argon-40 heavy ion beams with 140 MeV/nucleon with a series of increasingly polygonal carbon onions are investigated by high-resolution transmission electron microscopy and thermogravimetric analysis. The experimentally observed graphene layer linking is compared with expected results from the displacement and dislocation migration models. The results suggest that dislocation-driven mechanisms may play a significant role in graphene layer linking induced by heavy ion interactions with carbon onions.