The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

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Graphene photonics and optoelectronics

Raman spectroscopy of graphene and graphite: Disorder, electron phonon coupling, doping and nonadiabatic effects

The synthesis of carbon nanotubes with predefined structure and functionality plays a central role in the field of nanotechnology1,2, whereas the inhibition of carbon growth is needed to prevent a breakdown of industrial catalysts for hydrogen and synthesis gas production3. The growth of carbon nanotubes and nanofibres has therefore been widely studied4,5,6,7,8,9,10. Recent advances in in situ techniques now open up the possibility of studying gas–solid interactions at the atomic level11,12. Here we present time-resolved, high-resolution in situ transmission electron microscope observations of the formation of carbon nanofibres from methane decomposition over supported nickel nanocrystals. Carbon nanofibres are observed to develop through a reaction-induced reshaping of the nickel nanocrystals. Specifically, the nucleation and growth of graphene layers are found to be assisted by a dynamic formation and restructuring of mono-atomic step edges at the nickel surface. Density-functional theory calculations indicate that the observations are consistent with a growth mechanism involving surface diffusion of carbon and nickel atoms. The finding that metallic step edges act as spatiotemporal dynamic growth sites may be important for understanding other types of catalytic reactions and nanomaterial syntheses.

Atomic-scale imaging of carbon nanofibre growth

https://cyberleninka.org/article/n/323323.pdf

Production and processing of graphene and 2d crystals

We demonstrate inkjet printing as a viable method for large-area fabrication of graphene devices. We produce a graphene-based ink by liquid phase exfoliation of graphite in N-methylpyrrolidone. We use it to print thin-film transistors, with mobilities up to ∼95 cm2 V–1 s–1, as well as transparent and conductive patterns, with ∼80% transmittance and ∼30 kΩ/□ sheet resistance. This paves the way to all-printed, flexible, and transparent graphene devices on arbitrary substrates.

/pdf/inkjet-printed-graphene-electronics-57uspbuxaf.pdf

Inkjet-printed graphene electronics.

Structure of graphitic carbon on Ni(111): A surface extended-energy-loss fine-structure study

The electronic structure of carbon overlayers on Ni(111) has been investigated by using photoemission, energy-loss, and ionization-loss spectroscopy techniques. The combined use of these spectroscopies gives a detailed picture of these surfaces which have important catalytic implications. The carbidic carbon overlayer shows states at \ensuremath{\sim}1-, 4.2-, and 13-eV binding energy. Of particular significance is the detection (both in photoemission and in ionization-loss spectroscopy) of a carbon-derived state very near the Fermi level, in excellent agreement with recent theoretical predictions. The graphitic overlayer has an electronic structure very close to the electronic structure of pure graphite. We detect, however, an almost rigid shift of both valence and conduction bands which points to a charge transfer of about 0.02 electrons per carbon atom between the nickel substrate and the graphitic overlayer.

Electronic structure of carbidic and graphitic carbon on Ni(111)

The article describes the ESCA microscopy beamline dedicated to high spatial resolution quantitative and qualitative analysis on surfaces and interfaces. The scanning microscope is constructed to work both in transmission and photoemission within the photon energy range from 200 to 1200 eV with a spatial resolution of ∼0.1 μm. A Fresnel zone plate demagnifies the photon beam to submicrometer dimensions with 109–1010 photons/s in the focus spot. A photodiode and a hemispherical electron energy analyzer are used as detectors for recording the transmitted x‐rays and emitted photoelectrons, respectively. The operation modes in photoemission give the opportunity to obtain conventional energy distribution curve spectra from a microspot or a two‐dimensional micrograph of the spatial distribution and local concentration of a selected element as the sample is mechanically scanned. For conductive specimen topography measurements of a selected surface area probed by SPEM are possible using a scanning tunnelling microscope. The first test images of a zone plate and an e‐beam written specimen with 1 μm2 Au squares on Si have shown a spatial resolution better than 0.2 μm.

ESCA microscopy beamline at ELETTRA

The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of adsorbates on single crystal surfaces using soft x‐ray synchrotron radiation. It receives the light from an 81 period undulator with 5.6 cm period and 4.5 m length in the storage ring ELETTRA. The tunability of this insertion device, at a storage ring electron energy of 2.0 GeV and the connected modified SX700 monochromator allows the performance of experiments at this beamline in the photon energy range 100–2000 eV. This beamline is now operational and first absorption spectra are presented which show available resolving powers varying from 8000 to 3000 for photon energies between 240 and 850 eV.

Super ESCA: First beamline operating at ELETTRA

We report the first results obtained from the high energy resolution beam line at the storage ring ELETTRA of Trieste. The beam line has been designed to perform photoemission experiments in the vacuum ultraviolet (VUV) and soft X-ray (SXR) energy range. The radiation source is an undulator which consists of three sections, with 36 periods and a period length of 12.5 cm. It allows scanning of an energy range 17–900 eV using the 1st, 3rd and 5th harmonics. The monochromator is a spherical grating type and the resolving power at 400 eV, estimated from the K-shell photoabsorption of the N2 molecule is well above 10 000. The spectra are better than any other spectra taken while operating with high flux, i.e. first order diffraction and grating not masked. Measurements taken at the oxygen and neon K-edges, the argon L23 edges and of the helium double ionization spectra, indicate that the resolution is excellent from 65 to 870 eV.

A. Savoia

Papers

Structure of graphitic carbon on Ni(111): A surface extended-energy-loss fine-structure study

Electronic structure of carbidic and graphitic carbon on Ni(111)

ESCA microscopy beamline at ELETTRA

Super ESCA: First beamline operating at ELETTRA

First results from the high energy resolution photoemission beam line at ELETTRA