Ultraviolet-visible absorption measurements of high purity and well separated carbon onion samples are reported. The results show that, after purification, absorption features from carbon onions match well with the interstellar UV spectrum. The measurements show that the absorption peak position remains constant at 4.55+/-0.1 microm(-1), and the width varies from 1.2-1.6 microm(-1), a key feature of the interstellar spectrum. The similarities between the experimental and observed absorption spectra indicate that carbon onions are very strong candidates for the origin of the UV interstellar absorption peak at 4.6 microm(-1).

No abstract

We report on the fabrication of multiwalled carbon nanotube (MWCNT) bridges using poly-methylmethacrylate (PMMA) suspended dispersion. This method makes it possible to suspend nanotubes between metal electrodes, without any chemical etching of the substrate, and to remove unwanted nanotubes from the substrate. Using a spacer layer of PMMA with a known thickness, it is also possible to control the suspended height of the MWCNT bridges. The electrical measurement results on suspended MWCNT bridges reveals that the room temperature resistance ranges from under a kΩ to a few MΩ, with the majority around 2–4 kΩ. It was shown that a plasma-enhanced chemical vapor deposition grown MWCNT with a diameter ∼55 nm can sustain current densities of ∼108 A/cm2, which will make them suitable for applications as integrated field emission cathodes.

We have succeeded in synthesizing vertically aligned thin multi-walled carbon nanotubes (VA thin-MWCNTs) by a catalytic chemical vapor deposition (CCVD) method onto Fe/Al thin film deposited on a Si wafers using an optimum amount of hydrogen sulfide (H 2 S) additive. Scanning electron microscope (SEM) images revealed that the as-synthesized CNT arrays were vertically well-oriented perpendicular to the substrate with relatively uniform length. Transmission electron microscope (TEM) observations indicated that the as-grown CNTs were nearly catalyst-free thin-MWCNTs with small outer diameters of less than 10nm.The average wall number is about 5. We suggested a possible growth mechanism of the VA thin-MWCNT arrays. The VA thin-MWCNTs showed a low turn-on electric field of about 1.1 V/μm at a current density of 0.1 μA/cm 2 and a high emission current density about 2.5 mA/cm 2 at a bias field of 2.7 V/μm. Moreover, the VA thin-MWCNTs presented better field emission stability without degradation over 20 hours (h) at the emission current density of about 1 mA/cm 2 .