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Direct formation of large-area carbon thin films on gallium nitride by chemical vapor deposition without metallic catalysts is demonstrated. A high flow of ammonia is used to stabilize the surface of the GaN (0001)/sapphire substrate during the deposition at 950^\circC. Various characterization methods verify that the synthesized thin films are largely sp^2 bonded, macroscopically uniform, and electrically conducting. The carbon thin films possess optical transparencies comparable to that of exfoliated graphene. This paper offers a viable route toward the use of carbon-based materials for future transparent electrodes in III-nitride optoelectronics, such as GaN-based light emitting diodes and laser diodes. [ABSTRACT FROM PUBLISHER]

In this paper, we demonstrated a roughness dependent chemical vapor deposition (CVD) process to selectively grow aligned carbon nanotube bundles on silicon substrates with microscratches. Our results show that the aligned nanotubes of uniform length (around 2 μm) and diameter (20~30 nm) are assembled to nanotube bundles and in-plane vertically aligned with the microscratches. The microscratch-selective nanotube growth offers a promising approach for the fabrication of 3-D nanotube architectures in a single CVD process. [ABSTRACT FROM AUTHOR]

Large-area uniform carbon films with graphene-like properties are synthesized by chemical vapor deposition directly on Si3N4/Si at 1000 °C without metal catalysts. The as deposited films are atomically thin and wrinkle- and pinhole-free. The film thickness can be controlled by modifying the growth conditions. Raman spectroscopy confirms the sp2 graphitic structures. The films show ohmic behavior with a sheet resistance of ∼2.3-10.5 kΩ/□ at room temperature. An electric field effect of ∼2-10% (VG=-20 V) is observed. The growth is explained by the self-assembly of carbon clusters from hydrocarbon pyrolysis. The scalable and transfer-free technique favors the application of graphene as transparent electrodes. [ABSTRACT FROM AUTHOR]

Electron emission measurements were conducted on individual carbon nanotubes. The nanotubes had a closed end and their surfaces were thoroughly cleaned. It is shown conclusively that individual carbon nanotube electron emitters indeed exhibit Fowler–Nordheim behavior and have a work function of 5.1±0.1 eV for the nanotubes under investigation, which had diameters of 1.4 and 4.9 nm. [ABSTRACT FROM AUTHOR]

To communicate, spacecraft and satellites rely on microwave devices, which at present are based on relatively inefficient thermionic electron sources that require heating and cannot be switched on instantaneously. Here we describe a microwave diode that uses a cold-cathode electron source consisting of carbon nanotubes and that operates at high frequency and at high current densities. Because it weighs little, responds instantaneously and has no need of heating, this miniaturized electron source should prove valuable for microwave devices used in telecommunications. [ABSTRACT FROM AUTHOR]