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Graphene has attracted considerable interest as a potential new electronic material [1][2][3][4][5][6][7][8][9][10][11] . With its high carrier mobility, graphene is of particular interest for ultrahigh-speed radio-frequency electronics [12][13][14][15][16][17][18] . However, conventional device fabrication processes cannot readily be applied to produce high-speed graphene transistors because they often introduce significant defects into the monolayer of carbon lattices and severely degrade the device performance [19][20][21] . Here we report an approach to the fabrication of high-speed graphene transistors with a self-aligned nanowire gate to prevent such degradation. A Co 2 Si-Al 2 O 3 core-shell nanowire is used as the gate, with the source and drain electrodes defined through a self-alignment process and the channel length defined by the nanowire diameter. The physical assembly of the nanowire gate preserves the high carrier mobility in graphene, and the selfalignment process ensures that the edges of the source, drain and gate electrodes are automatically and precisely positioned so that no overlapping or significant gaps exist between these electrodes, thus minimizing access resistance. It therefore allows for transistor performance not previously possible. Graphene transistors with a channel length as low as 140 nm have been fabricated with the highest scaled on-current (3.32 mA mm 21 ) and transconductance (1.27 mS mm 21 ) reported so far. Significantly, on-chip microwave measurements demonstrate that the self-aligned devices have a high intrinsic cut-off (transit) frequency of f T 5 100-300 GHz, with the extrinsic f T (in the range of a few gigahertz) largely limited by parasitic pad capacitance. The reported intrinsic f T of the graphene transistors is comparable to that of the very best high-electron-mobility transistors with similar gate lengths 10 .With the highest carrier mobility, exceeding 200,000 cm 2 V 21 s 21 (ref. 8), and many other desirable properties, including a large critical current density (,2 3 10 8 A cm 22 (ref. 22)) and a high saturation velocity (5.5 3 10 7 cm s 21 (ref. 11)), graphene has significant potential for high-speed electronics to offer excellent radio-frequency characteristics with very high cut-off frequency (f T ). Importantly, recent studies have demonstrated graphene transistors operating in the gigahertz regime [12][13][14][16][17][18] with a record of f T 5 100 GHz (ref. 13). However, the reported radio-frequency performance so far is still far from the potential that the graphene transistors may offer, and is primarily limited by two adverse factors in the device fabrication process.The first limitation is associated with the severe mobility degradation resulting from the graphene-dielectric integration process, which introduces substantial defects into pristine graphene lattices 20,23 . To overcome this, we have recently developed a strategy to integrate high-quality, high-dielectric-constant dielectrics with graphene using a physical assembly approach without in...

A few-layer MoS2 photodetector driven by poly(vinylidene fluoride-trifluoroethylene) ferroelectrics is achieved. The detectivity and responsitivity are up to 2.2 × 10(12) Jones and 2570 A W(-1), respectively, at 635 nm with ZERO gate bias. E(g) of MoS2 is tuned by the ultrahigh electrostatic field from the ferroelectric polarization. The photoresponse wavelengths of the photodetector are extended into the near-infrared (0.85-1.55 μm).

Graphene has the potential for high-speed, wide-band photodetection, but only with very low external quantum efficiency and no spectral selectivity. Here we report a dramatic enhancement of the overall quantum efficiency and spectral selectivity that enables multicolour photodetection, by coupling graphene with plasmonic nanostructures. We show that metallic plasmonic nanostructures can be integrated with graphene photodetectors to greatly enhance the photocurrent and external quantum efficiency by up to 1,500%. Plasmonic nanostructures of variable resonance frequencies selectively amplify the photoresponse of graphene to light of different wavelengths, enabling highly specific detection of multicolours. Being atomically thin, graphene photodetectors effectively exploit the local plasmonic enhancement effect to achieve a significant enhancement factor not normally possible with traditional planar semiconductor materials.