The ability of graphene to transduce an adsorption event of ions into a detectable electrical signal has sparked a lot of interest for its use in sensors. However, a low concentration of the chemically active sites for binding analytes on the graphene surface has significantly prevented its applications so far. Here, we report on implementation of the van der Waals heterostructure based on a monolayer graphene and an ∼1-nm-thick molecular carbon nanomembrane (CNM) in a solution-gated field-effect transistor (FET) for pH sensing. The nondestructive functionalization of a graphene FET with the amino-terminated CNM (NH2-CNM) enables the induction of chemically active groups in the vicinity of the graphene sheet, maintaining its charge carrier transport properties. We applied complementary characterization techniques, including Raman spectroscopy, x-ray photoelectron spectroscopy, and optical and atomic force microscopy as well as field-effect and electrical impedance measurements to characterize the engineered NH2-CNM/graphene devices. We demonstrate their high pH resolution with a minimum detectable pH change of ∼0.01 at pH 2 and ∼0.04 at pH 12, with a response time in the range of seconds, and we apply an electrical double-layer model to rationalize the experimentally observed performance theoretically. The developed device concept enables the engineering of microscale pH sensors for applications in biological and environmental sciences.

We demonstrate graphene electro-absorption modulators (EAM) integrated on 300mm wafers. The integration is based on imec’s 300mm silicon photonics platform and the full integration sequence is using standard CMOS production tools expect for the 6-inch CVD graphene growth and transfer, transferred by Graphenea. 164x TE EAMs were measured per wafer and demonstrate 90% yield with modulation efficiency (ME) of 41±5.6 dB/mm for 8V voltage swing, after process optimization. The 3dB bandwidth of the EAMs is 14.9±1.2 GHz for the device with 50µm active length. Both parameters show comparable performance with lab-based devices, obtained on coupons using similar CVD graphene. This work paves the way to enable high-volume manufacturing of 2D-material-based photonics devices.

An electrode for the oxygen evolution reaction based on a conductive bi-layered free standing graphene support functionalized with iridium nanoparticles was fabricated and characterized by means of potentiometric and advanced X-ray spectroscopic techniques. It was found that the electrocatalytic activity of iridium nanoparticles is associated to the formation of Ir 5d electron holes. Strong Ir 5d and O 2p hybridization, however, leads to a concomitant increase O 2p hole character, making oxygen electron deficient and susceptible to nucleophilic attack by water. Consequently, more efficient electrocatalysts can be synthesized by increasing the number of electron-holes shared between the metal d and oxygen 2p.

GRACE Developing electrical characterisation methods for future graphene electronics is a 2016 Normative Joint Research Project of the European Metrology Programme for Innovation and Research. The project focuses on the measurement of the electrical properties of graphene. Its objectives are to develop validated measurement methods and protocols, including fast-throughput examples. The work is performed in collaboration with international standardisation committees, with an aim to initiate and develop dedicated documentary standards.

The original version of this article unfortunately contained an error. The authors would like to correct the error with this erratum. In Fig. 5 the process C and B were incorrectly labelled. The corrected Fig. 5 with the right labelling is included in this erratum.

Graphene (Gr) is currently one of the most appealing materials as conductive transparent electrode for flexible electronics, thanks to its bendability/stretchability accompanied by small variations of the electrical properties after mechanical deformations. In addition, the field-effect tunable carrier density combined to a high mobility and saturation velocity make it an excellent channel material for field-effect transistors (FETs) even on flexible substrates. By proper design of the device structure (channel length, top- or back-gate configuration), Gr-FETs can be used for high-frequency (RF) electronics or for high-sensitivity chemical, biological, and environmental sensors exploiting transconductance variations in response to the chemi/physisorption of molecular species on Gr channel. In particular, miniaturized and flexible Gr-FET sensors can represent a strong advance with respect to current sensors technology and will be extremely useful for “in situ” applications. Here we report a wafer scale and semiconductor fab compatible processing strategy to fabricate arrays of Gr-FETs on a PEN substrate, adopting a local back-gate configuration, with a thin Al2O3 gate dielectric film deposited at low temperature (100 °C) by plasma-assisted Atomic Layer Deposition (ALD) and transfer of large-area Gr grown by chemical vapor deposition on copper foils. Electrical characterization of the fabricated devices is presented and their suitability for solid ion sensing FET (IS-FET) applications is discussed.

The precise value of the g factor in graphene is of fundamental interest for all spin-related properties and their application. We investigate monolayer graphene on a Si/SiO_{2} substrate by resistively detected electron spin resonance. Surprisingly, the magnetic moment and corresponding g factor of 1.952±0.002 is insensitive to charge carrier type, concentration, and mobility.

One of the main goals in catalysis is the characterization of solid/gas interfaces in a reaction environment. The electronic structure and chemical composition of surfaces become heavily influenced by the surrounding environment. However, the lack of surface sensitive techniques that are able to monitor these modifications under high pressure conditions hinders the understanding of such processes. This limitation is known throughout the community as the "pressure gap." We have developed a novel experimental setup that provides chemical information on a molecular level under atmospheric pressure and in presence of reactive gases and at elevated temperatures. This approach is based on separating the vacuum environment from the high-pressure environment by a silicon nitride grid-that contains an array of micrometer-sized holes-coated with a bilayer of graphene. Using this configuration, we have investigated the local electronic structure of catalysts by means of photoelectron spectroscopy and in presence of gases at 1 atm. The reaction products were monitored online by mass spectrometry and gas chromatography. The successful operation of this setup was demonstrated with three different examples: the oxidation/reduction reaction of iridium (noble metal) and copper (transition metal) nanoparticles and with the hydrogenation of propyne on Pd black catalyst (powder).

Graphene exhibits very high carrier mobility, photocarrier short lifetime and broadband absorption. As graphene technology is CMOS compatible, graphene devices offer a viable low cost alternative for high frequency electronic and optoelectronic devices [1]. Thanks to low propagation losses, electromagnetic immunity and large bandwidth operation, optical signals are advantageously coupled with electrical signals for high-rate communication systems on optical fibers. This leaded to the large development of optoelectronic devices based on 3-5 semiconductors and operating at 1.55 μm telecom wavelength. We have fabricated a high frequency optoelectronic device that operates with optical signals at 1.55 μm and with microwave electrical signals (see figure and [2]). This is a coplanar waveguide integrating a CVD graphene layer that is passivated with an atomic-layer-deposited Al2O3 film. As a consequence the graphene Fermi level can be easily controlled with the silicon substrate bias even if the graphene layer and the substrate are separated by a 2 μm thick SiO2 layer. We operated this device as a high frequency photodetector and demonstrated a flat response up to 40 GHz. Moreover, using up to 30 GHz optical signals at 1.55 μm and up to 30 GHz microwave signals, we showed optoelectronic mixing. Thanks to this feature, a high-frequency intensity-modulated optical signal at frequency fopt can be photodetected and mixed with an electrical carrier at frequency fele. It produces up and down-converted signals, at frequencies fopt + fele and | fopt – fele |, respectively. These results open interesting prospective in the domain of low cost telecommunication systems. References [1] A. C. Ferrari, et al., Nanoscale, 7, 4598 (2015). [2] A. Montanaro et al., “30 GHz optoelectronic mixing in CVD graphene”, Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b05141

Researchers demonstrate graphene plasmon edge modes at infrared wavelengths. Such modes may offer additional electromagnetic field confinement compared with conventional sheet modes. Plasmons in graphene nanoresonators have many potential applications in photonics and optoelectronics, including room-temperature infrared and terahertz photodetectors, sensors, reflect arrays or modulators1,2,3,4,5,6,7. The development of efficient devices will critically depend on precise knowledge and control of the plasmonic modes. Here, we use near-field microscopy8,9,10,11 between λ0 = 10–12 μm to excite and image plasmons in tailored disk and rectangular graphene nanoresonators, and observe a rich variety of coexisting Fabry–Perot modes. Disentangling them by a theoretical analysis allows the identification of sheet and edge plasmons, the latter exhibiting mode volumes as small as 10−8λ03. By measuring the dispersion of the edge plasmons we corroborate their superior confinement compared with sheet plasmons, which among others could be applied for efficient 1D coupling of quantum emitters12. Our understanding of graphene plasmon images is a key to unprecedented in-depth analysis and verification of plasmonic functionalities in future flatland technologies.

In this work we present the effect of defects in graphene on its potential for application in flexible electronics. We visualize defects at the grain boundaries, transfer defects and local atomic defects. We show that these defects are currently determining the gas barrier properties of graphene. Under strain up to only 2% we show that these defects lead to cracks in the graphene thereby deteriorating its conductivity.

Controlling the energy flow processes and the associated energy relaxation rates of a light emitter is of fundamental interest and has many applications in the fields of quantum optics, photovoltaics, photodetection, biosensing and light emission. Advanced dielectric, semiconductor and metallic systems have been developed to tailor the interaction between an emitter and its environment. However, active control of the energy flow from an emitter into optical, electronic or plasmonic excitations has remained challenging. Here, we demonstrate in situ electrical control of the relaxation pathways of excited erbium ions, which emit light at the technologically relevant telecommunication wavelength of 1.5 μm. By placing the erbium at a few nanometres distance from graphene, we modify the relaxation rate by more than a factor of three, and control whether the emitter decays into electron–hole pairs, emitted photons or graphene near-infrared plasmons, confined to <15 nm from the graphene sheet. These capabilities to dictate optical energy transfer processes through electrical control of the local density of optical states constitute a new paradigm for active (quantum) photonics and can be applied using any combination of light emitters and two-dimensional materials.

In the present work, the dry sliding behavior of a graphene/alumina composite material was studied against alumina in air. The tests were carried out in a reciprocating wear tester with an applied load of 20 N, a sliding speed of 0.06 m s−1 and a sliding distance of up to 10 km. Under the testing conditions, the graphene/ceramic composite showed approximately half the wear rate and a 10% lower friction coefficient than the monolithic alumina. It has been found that this behavior is related to the presence of graphene platelets adhered to the surface of friction that form a self-lubricating layer which provides enough lubrication in order to reduce both wear rate and friction coefficient, as compared to the alumina/alumina tribological system.

Graphene plasmons promise unique possibilities for controlling light in nanoscale devices and for merging optics with electronics. We developed a versatile platform technology based on resonant optical antennas and conductivity patterns for launching and control of propagating graphene plasmons, an essential step for the development of graphene plasmonic circuits. We launched and focused infrared graphene plasmons with geometrically tailored antennas and observed how they refracted when passing through a two-dimensional conductivity pattern, here a prism-shaped bilayer. To that end, we directly mapped the graphene plasmon wavefronts by means of an imaging method that will be useful in testing future design concepts for nanoscale graphene plasmonic circuits and devices.

, 1366 (2014); 344 Science et al. J.-P. Tetienne nitrogen-vacancy center microscope Nanoscale imaging and control of domain-wall hopping with a This copy is for your personal, non-commercial use only. clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles ): June 19, 2014 www.sciencemag.org (this information is current as of The following resources related to this article are available online at http://www.sciencemag.org/content/344/6190/1366.full.html version of this article at: including high-resolution figures, can be found in the online Updated information and services, http://www.sciencemag.org/content/suppl/2014/06/18/344.6190.1366.DC1.html can be found at: Supporting Online Material http://www.sciencemag.org/content/344/6190/1366.full.html#ref-list-1 , 4 of which can be accessed free: cites 35 articles This article

A simple, fast and upscalable method is described to produce graphene/alumina (G/Al2O3) composites by spark plasma sintering (SPS) with a significant improvement on both mechanical and electrical properties of monolithic Al2O3. Graphene oxide (GO) was mixed with Al2O3 using a colloidal method obtaining an excellent dispersion of GO in the alumina matrix. The material was consolidated by SPS that allowed, in one-step, the in situ reduction of the GO during the sintering process. A detailed Raman analysis was found to be very useful to study the orientation of the graphene in the composite and to evaluate and optimise its thermal reduction. Graphene platelets acted as elastic bridges avoiding crack propagation and providing this material with a crack bridging reinforcement mechanism. A very low graphene loading (0.22wt%) led to a 50% improvement on the mechanical properties of the alumina and to an increase of the electrical conductivity up to eight orders of magnitude.

Electrode materials combining high electrical conductivity and optical transparency are crucial components for organic light emitting diodes (OLED). Graphene is thereby a highly promising alternative to commonly used Indium tin oxide (ITO), in particular considering that unlike ITO graphene is flexible and, when grown via Chemical Vapor Deposition (CVD), not constraint by limited natural resources. Critical challenges for graphene based OLEDs not only relate to the further improvement of large-area, controlled graphene CVD [1,2], but also to its integration, in particular to achieve efficient charge injection and graphene doping. Several dopants have recently been introduced, but most are chemically not stable or not applicable for organic electronic devices. Figure 1: Scheme of OLEDs with ITO electrode and graphene electrode. Here we show that transition metal oxides, such as MoO3, are very efficient and stable p-type dopants for graphene which can be easily integrated in the OLED fabrication process. Our process is based on scalable graphene CVD [1,2] and the doping is carried out via thermal evaporation analogous to all following OLED layers. With in-situ 4-point probe measurements we find that only a few nanometers of MoO3 are sufficient for efficient doping leading to a more than three-fold improved sheet resistance. In addition, ultra-violet and x-ray photoemission spectroscopy (UPS, XPS) studies of the doping process reveal a large interface dipole of 2.2 eV and band bending caused by an electron transfer from graphene to MoO3. The strong p-doping of graphene is enforced by the deep lying electronic states of MoO3 which exhibits a work function of >6.5 eV.[3] The energy level alignment at the graphene/MoO3/organic interfaces as measured with UPS shows only very small energy barriers for hole-injection. Thus, MoO3 allows not only an efficient p-doping of graphene, but also provides a suitable matching for efficient hole-injection from graphene into the OLED layers. Based on this process, we demonstrate CVD graphene based OLEDs that show electro-optical performances similar to conventional ITO based devices, as shown in Figure 2. Figure 2: Current efficiency vs. voltage characteristics of OLEDs with ITO and graphene electrode, respectively.

Raman spectroscopy and X-ray diffraction are used to study the crystalline structure of carbon–carbon and TiC-containing composites. The advantages and drawbacks of these techniques for the characterisation of carbon–carbon composites are analysed in the light of the distribution and arrangement of their components and the microstructural orientation of the supporting matrix. Analyses performed on longitudinal and transverse sections of the composites confirm that the measurements are affected by the orientation of the crystals. The overall crystalline parameters calculated by X-ray diffraction were unequivocally resolved for each single component by means of Raman spectroscopy. A significantly higher degree of order was observed in the TiC-containing matrix as a result of the catalytic graphitisation of the carbon achieved by the addition of titanium. In addition, Raman spectroscopy corroborated that the incorporation of TiC into the carbon matrix does not disrupt the orientation of the graphene planes of the matrix parallel to the fibre axis, a necessary characteristic for achieving an optimum heat transfer through the material.

Titanium-doped CC composites were prepared by liquid impregnation of a 2D carbon fibre preform using a mesophase pitch doped with TiC nanoparticles as matrix precursor. The effect of the addition of titanium carbide on the microstructure and thermal properties of CC composites is investigated. A higher degree of order was developed in the matrix of the Ti-doped composite which is the result of the catalytic graphitisation of carbon promoted by titanium. As a consequence, the thermal conductivity is higher in this doped material, despite the low dopant content introduced in the matrix, which points out the relevant contribution of the matrix to the thermal properties of the whole composite.

In spite of the remarkable progress in the design of in-vessel components for the divertor of the first International Thermonuclear Experimental Reactor (ITER), a great effort is still put into the development of manufacturing technologies for carbon armour with improved properties. Newly developed 3D titanium-doped carbon fibre reinforced composites and their corresponding undoped counterparts were brazed to a CuCrZr heat sink to produce actively cooled flat tile mock-ups. By exposing the mock-ups to thermal fatigue tests in an electron beam test facility, the material behaviour and the brazing between the individual constituents in the mock-up was qualified. The mock-ups with titanium-doped CFCs exhibited a significantly improved thermal fatigue resistance compared with those undoped materials. The comparison of these mock-ups with those produced using pristine NB31, one of the reference materials as plasma facing material for ITER, showed almost identical results, indicating the high potential of Ti-doped CFCs due to their improved thermal shock resistance.