ABSTRACT:Integrated circuits based on CMOS (complementary metal-oxide semiconductors) are at the heart of the technological revolution of the past 40 years, as these have enabled compact and low cost micro-electronic circuits and imaging systems. However, the diversification of this platform into applications other than microcircuits and visible light cameras has been impeded by the difficulty to combine other semiconductors than silicon with CMOS. Here, we show for the first time the monolithic integration of a CMOS integrated circuit with graphene, operating as a high mobility phototransistor. We demonstrate a high-resolution image sensor and operate it as a digital camera that is sensitive to UV, visible and infrared light (300 -2000 nm). The demonstrated graphene-CMOS integration is pivotal for incorporating 2d materials into the next generation microelectronics, sensor arrays, low-power integrated photonics and CMOS imaging systems covering visible, infrared and even terahertz frequencies.2

We investigated thermal conductivity of free-standing reduced graphene oxide films subjected to a high-temperature treatment of up to 1000°C. It was found that the hightemperature annealing dramatically increased the in-plane thermal conductivity, K, of the films from ~3 W/mK to ~61 W/mK at room temperature. The cross-plane thermal conductivity, K  , revealed an interesting opposite trend of decreasing to a very small value of ~0.09 W/mK in the reduced graphene oxide films annealed at 1000 o C. The obtained films demonstrated an exceptionally strong anisotropy of the thermal conductivity, K/K  ~ 675, which is substantially larger even than in the high-quality graphite. The electrical resistivity of the annealed films reduced to 1 / -19 /. The observed modifications of the in-plane and cross-plane thermal conductivity components resulting in an unusual K/K  anisotropy were explained theoretically. The theoretical analysis suggests that K can reach as high as ~500 W/mK with the increase in the sp 2 domain size and further reduction of the oxygen content. The strongly anisotropic heat conduction properties of these films can be useful for applications in thermal management.  Corresponding author (AAB): balandin@ee.ucr.edu ; web: http://ndl.ee.ucr.edu/ University of California -Riverside and Graphenea Inc. (2015) 2 | P a g e

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.

Plasmons in graphene nanoresonators have large application potential in photonics and optoelectronics, including room-temperature infrared and terahertz photodetectors, sensors, reflect-arrays or modulators [1][2][3][4][5][6][7] . Their efficient design will critically depend on the precise knowledge and control of the plasmonic modes. Here, we use near-field microscopy 8-11 between λ = 10 to 12 m wavelength 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 for identifying sheet and edge plasmons, the later exhibiting mode volumes as small as 10 λ . By measuring the dispersion of the edge plasmons we corroborate their superior confinement compared to sheet plasmons, which among others could be applied for efficient 1D coupling of quantum emitters 12 . Our understanding of graphene plasmon images is a key to unprecedented in-depth analysis and verification of plasmonic functionalities in future flatland technologies.2 At infrared and terahertz frequencies, doped graphene can support electrically tunable graphene plasmons (GPs) -electromagnetic fields coupled to charge carrier oscillations -with extremely short wavelengths and large confinement [13][14][15][16][17] . For that reason, graphene has a great potential for controlling radiation on the nanometer scale 18 , which largely benefits the development of highly sensitive spectroscopy 3 and detection [19][20][21] applications. The electromagnetic field concentration achieved by GPs can be further enhanced by fabricating nanostructures acting as Fabry-Perot resonators for GPs (for example disks or ribbons) 1,2, 6, 7,22 , favoring strong absorption in arrays of the resonators (up to 40%) 7 . Until now, localized plasmonic modes in graphene ribbons and disks have been analyzed experimentally essentially by far-field spectroscopy 1,2, 6, 7,22 . With this technique, however, neither the mode structure, nor the unique plasmonic edge modes are accessible. A comprehensive experimental characterization of graphene plasmonic nanoresonators and their sheet and edge modes has thus been elusive so far. On the other hand, plasmonic edge modes have been shown to propagate along sharp edges of gold films, graphene and 2D electron gases 11,[23][24][25][26][27][28] and provide stronger confinement of the electromagnetic fields compared to the sheet plasmons.Here we image and analyze the near-field structure of both plasmonic sheet and edge modes in graphene disks and rectangular nanoresonators. We employ scattering-type scanning near-field optical microscopy (s-SNOM) 29 , which to date is the only available tool for real-space imaging of the propagation and confinement characteristics of graphene plasmons 8,9,11 . The lack of a detailed understanding of graphene-plasmonic s-SNOM contrasts, however, has not allowed yet for a comprehensive analysis of plasmon modes in graphene nanostructures. We tackled this problem by three-dimensi...

The significant progress in terms of fabricating large-area graphene films for transparent electrodes, barriers, electronics, telecommunication and other applications has not yet been accompanied by efficient methods for characterizing the electrical properties of large-area graphene. While in the early prototyping as well as research and development phases, electrical test devices created by conventional lithography have provided adequate insights, this approach is becoming increasingly problematic due to complications such as irreversible damage to the original graphene film, contamination, and a high measurement effort per device. In this topical review, we provide a comprehensive overview of the issues that need to be addressed by any large-area characterisation method for electrical key performance indicators, with emphasis on electrical uniformity and on how this can be used to provide a more accurate analysis of the graphene film. We review and compare three different, but complementary approaches that rely either on fixed contacts (dry laser lithography), movable contacts (micro four point probes) and non-contact (terahertz timedomain spectroscopy) between the probe and the graphene film, all of which have been optimized for maximal throughput and accuracy, and minimal damage to the graphene film. Of these three, the main emphasis is on THz time-domain spectroscopy, which is non-destructive, highly accurate and allows both conductivity, carrier density and carrier mobility to be mapped across arbitrarily large areas at rates that by far exceed any other known method. We also detail how the THz conductivity spectra give insights on the scattering mechanisms, and through that, the microstructure of graphene films subject to different growth and transfer processes. The perspectives for upscaling to realistic production environments are discussed. TOPICAL REVIEWOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.

No abstract

Controlling the energy flow processes and the associated energy relaxation rates of a light emitter is of high fundamental interest, and has many applications in the fields of quantum optics, photovoltaics, photodetection, biosensing and light emission. While advanced dielectric and metallic systems have been developed to tailor the interaction between an emitter and its environment, active control of the energy flow 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 either electron-hole pairs, emitted photons or graphene near-infrared plasmons, confined to <15 nm to the 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.Spontaneous emission constitutes a canonical example of energy flow from an excited light emitter into its environment, where energy relaxation takes place via photon emission. Alternatively, for an emitter in the vicinity of a solid, energy relaxation can occur through channels involving electronic excitations, such as electron-hole pairs and collective charge oscillations (plasmons). Tailoring spontaneous emission by modifying the local density of optical states (LDOS), which governs the emitter-environment interactions [1,2], has been achieved using, amongst others, optical cavities [3][4][5][6], photonic crystals [7,8], and metallic nanostructures [9]. In these systems the LDOS available for the light emitters is typically a fixed property that depends only on the type and geometry of the material system. Here, we control electrically and in-situ the local density of optical states and therefore the energy relaxation rate of a nearby emitter, by employing graphene. Specifically, we demonstrate in-situ tuning of the magnitude and character of the energy transfer pathways from optically excited erbium ions -emitters for near-infrared light that are used as a gain medium in telecommunication applications [10,13]. This control enables new avenues in a range of fields, covering photovoltaics [11,12] The ability to control in-situ the LDOS requires a material for which the optical excitations that occur for a specific emission energy can be modified. Because graphene is gapless and it has a Fermi energy that is electrostatically tunable up to optical energies of ∼1 eV, it can effectively behave as a semiconductor, a dielectric, or a metal. Here, we propose to use these material characteristics to electrically control the relaxation rate and energy transfer processes of a dipolar emitter at subwavelength distance from the graphene. The concept of our experiment is shown in Fig. 1a, schematically representing the gate-tunable ener...

We investigated toxicity of 2–3 layered >1 μm sized graphene oxide (GO) and reduced graphene oxide (rGO) in mice following single intratracheal exposure with respect to pulmonary inflammation, acute phase response (biomarker for risk of cardiovascular disease) and genotoxicity. In addition, we assessed exposure levels of particulate matter emitted during production of graphene in a clean room and in a normal industrial environment using chemical vapour deposition. Toxicity was evaluated at day 1, 3, 28 and 90 days (18, 54 and 162 μg/mouse), except for GO exposed mice at day 28 and 90 where only the lowest dose was evaluated. GO induced a strong acute inflammatory response together with a pulmonary (Serum-Amyloid A, Saa3) and hepatic (Saa1) acute phase response. rGO induced less acute, but a constant and prolonged inflammation up to day 90. Lung histopathology showed particle agglomerates at day 90 without signs of fibrosis. In addition, DNA damage in BAL cells was observed across time points and doses for both GO and rGO. In conclusion, pulmonary exposure to GO and rGO induced inflammation, acute phase response and genotoxicity but no fibrosis.