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Doping in epitaxial graphene (EG) is challenging because of the high-temperature process and the ultra-thin nature of graphene. In this work, a facile one-step method is demonstrated to generate doping in EG with bismuth (Bi) during thermal decomposition of SiC, in which Bi atom flux acts as the doping source. Raman spectroscopy and scanning tunneling microscopy/spectroscopy are employed to characterize the quality, morphology and electronic properties of Bi doped EG. Both the intercalated and incorporated Bi atoms can be considered as dopants. It was found that the Dirac point shifts away from the Fermi level as a result of electron transfer from Bi to EG, and thus enhances the n-doping behavior of EG significantly. First principles calculations were done to address the enhanced n-doping of EG by Bi. This in-situ doping procedure can be extended to other metals, showing great potential applications in tailoring the performance of EG and significance to electronics in the future. [ABSTRACT FROM AUTHOR]

Ferroelectric-field-effect-tunable modulation of terahertz waves in graphene/Si:HfO2/Si stack structure was observed. The modulation shows distinct behaviors when the samples under different gate polarities. At a negative voltage, a transmission modulation depth up to ~74% was present without depending on the photo illumination power, whereas, at a positive voltage, the modulation of Thz wave shows dependence on the illumination power, which is ascribed to the creation/ elimination of an extra barrier in Si layer in response to the polarization in the ferroelectric Si:HfO2 layer. Considering the good compatibility of HfO2 on Si-based semiconductor process, the ferroelectricity layer of Si:HfO2 may open up an avenue for the tunable modulation of Thz wave. [ABSTRACT FROM AUTHOR]

The graphene-based photodetector with tunable p-p+-p junctions was fabricated through a simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiated graphene (LIG) junction by scanning photocurrent measurements, and its magnitude can be modulated as a result of a positive correlation between the photocurrent and doping concentration in LIG region. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junctions. Such a simple and low-cost technique offers an alternative way for the fabrication of graphene-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report a highly tunable graphene embedded waveguide which overall modal index is in linear relationship with the in-plane permittivity of graphene and the electro-refraction effect has been significantly enhanced after graphene is embedded. An eight-layer graphene embedded Mach-Zender modulator has been theoretically demonstrated with the advantage of ultra-compact footprint (4 × 30 μm2), high modulation efficiency (20 V·μm), fast modulation speed, and large extinction ratio (35 dB). Our results may promote various on-chip active components, boosting the utilization of graphene in optical applications. [ABSTRACT FROM AUTHOR]

We demonstrate a simple fabrication method to produce randomly stacked graphene chemiresistors using surfactant-assisted exfoliation of graphite. We analyze the sensitivity of such chemiresistors as a function of vacuum filtration volume and temperature. At low vacuum filtration volumes (<∼5 mL) the sensors exhibit superior sensitivity towards target molecules compared to previously developed polycrystalline graphene, polycrystalline graphene microribbon, and carbon nanotube chemical sensors. Temperature dependent measurements, transmission electron microscopy and scanning electron microscopy suggest the improved sensitivity in the randomly stacked graphene chemiresistors is due to 2-dimensional charge carrier hopping through edge defects. [ABSTRACT FROM AUTHOR]

We investigate the transport properties of a four-terminal graphene device of which two terminals are beneath a pair of reversal top gate voltages. We find there exists quantum Hall-like effect without magnetic field applied. The curve of Hall conductance versus the Fermi energy shows steps, and the disorder can make the steps clearer. The average length of Hall conductance plateaus is of the order meV for the devices with the terminal widths of the order μm, which is within the scope of the experimental observation. The influences of gate voltage, device dimensions, and dispersion gap are also discussed. [ABSTRACT FROM AUTHOR]

We report a device that combines indium tin oxide (ITO) nanodot nodes with two-dimensional chemically converted graphene (CCG) films to yield a GaN-based light emitting diode (LED) with interesting characteristics for transparent and current spreading electrodes for the potential use in the ultraviolet region. The current-voltage characteristics and electroluminescence output power performance showed that CCG network on ITO nanodot nodes operated as a transparent and current spreading electrode in LED devices. [ABSTRACT FROM AUTHOR]

In this report, we find multilayered graphene, which has good transparency, conductivity and suitable work function, can be used as the anode for the organic light emitting device. Our device structure is Al/glass/multilayered graphene/V2O5/NPB/CBP:(ppy)2Ir(acac)/Bphen/Bphen:Cs2CO3/Sm/Au. The maximum luminance efficiency and maximum power efficiency reach 0.75 cd/A and 0.38 lm/W, respectively. We believe that by optimizing the hole density and uniforming the thickness of the multilayered graphene anode, the device efficiency can be remarkably increased in the future. [ABSTRACT FROM AUTHOR]