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Submicrometric catalyst patterns have been fabricated by atomic force nanolithography and the subsequent selective growth of carbon nanotubes has been successfully verified. Rectangular stripes (∼350 nm wide) were engraved onto a polymethylmethacrylate film, deposited onto SiO2/Si, by polymer removal with atomic force microscopy nanoindentation. Metallic catalyst patterns were subsequently obtained after 3 nm Ni deposition and lift-off of the residual polymer. Multiwalled carbon nanotubes were then grown by thermal chemical vapor deposition onto the Ni stripes. The various steps of nanopatterning and of carbon nanotubes growth are also studied by scanning electron microscopy and Raman measurements. [ABSTRACT FROM AUTHOR]

We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate sidegating below 1V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10mV drain bias. We measure the planar leakage along the SiO2/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO2 up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices. [ABSTRACT FROM AUTHOR]

We report the observation and characterization of field emission current from individual single- and few-layer graphene flakes laid on a flat SiO2/Si substrate. Measurements were performed in a scanning electron microscope chamber equipped with nanoprobes which allowed local measurement of the field emission current. We achieved field emission currents up to 1 μA from the flat part of graphene flakes at applied fields of few hundred volt per micrometer. We found that the emission process is stable over a period of several hours and that it is well described by a Fowler-Nordheim model for currents over five orders of magnitude. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotube sheets of relatively large area have been grown on a sapphire substrate by chemical vapor deposition at the substrate temperature of 500 and 750 °C. The photoconductivity measurements, performed under white light and monochromatic radiation in the ultraviolet–visible–near infrared region, show that the highly defective sample grown at 500 °C has a higher photosensitivity, thus revealing the crucial role of structural defects in determining the overall photoresponse of the nanotube’s sheets. The spectral photoresponse of these nanostructured films increases with the increase in photon energy, and is strongly correlated to the absorbance. The photoconductivity properties of these materials are favorable in potential development of large area light sensors as well as optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]

We report on a significant photocurrent generation from a planar device made by growing simultaneously different strips of vertically and horizontally aligned multi-wall carbon nanotubes, obtained under white light and different wavelengths in the visible region. We show that the photocurrent of all strips increases with decreasing the strip length and, the highest photoconversion is found to be in the blue-shift visible region. This significant photocurrent generation at lower wavelengths is directly related to the absorbance properties of multi-wall carbon nanotubes and a Raman spectroscopy study confirms that the most part of innermost tubes have a semiconducting nature. [ABSTRACT FROM AUTHOR]