Field electron emission from vertically well-aligned zinc oxide ͑ZnO͒ nanowires, which were grown by the vapor deposition method at a low temperature of 550°C, was investigated. The high-purity ZnO nanowires showed a single crystalline wurtzite structure. The turn-on voltage for the ZnO nanowires was found to be about 6.0 V/m at current density of 0.1 A/cm 2. The emission current density from the ZnO nanowires reached 1 mA/cm 2 at a bias field of 11.0 V/m, which could give sufficient brightness as a field emitter in a flat panel display. Therefore, the well-aligned ZnO nanowires grown at such low temperature can promise the application of a glass-sealed flat panel display in a near future.

We report the synthesis of high-quality double-walled carbon nanotubes without defects by catalytic decomposition of alcohol over an Fe-Mo/Al2O3 catalyst; the synthesized DWNTs have outer diameters in the range of 1.52-3.54 nm and an average interlayer distance of 0.38 nm between graphene layers.

High-quality single-walled carbon nanotubes free of defects and amorphous carbon coating have been produced by catalytic decomposition of C2H2 over Fe-Mo/Al2O3 catalyst.

Multiwalled carbon nanotubes (MWCNTs) were expanded by 2.5 times in diameter through high-energy (MeV) ion irradiation. Pristine MWCNTs were synthesized onto SiO 2 substrate by chemical vapor deposition. The 4 MeV Cl 2+ ions with a dose of 3 ϫ 10 16 ions/ cm 2 were irradiated on MWCNTs. From high-resolution transmission electron microscopy (HR-TEM) images, the average diameter of the high-energy-ion-irradiated MWCNTs was ϳ180 nm, while that of the pristine MWCNTs was ϳ70 nm. The wall thickness of the pristine and the high-energy-ion-irradiated MWCNT samples was ϳ20 nm and 40-50 nm, respectively. We observed the clear formation of nanocompartments with bamboolike structure inside the tubes after ion irradiation. The amorphous carbon structure in the ion-irradiated MWCNT shells was observed from Raman spectra. Based on the results of HR-TEM and Raman spectra, the expansion of the systems represents morphological transition from crystalline graphite structure to amorphous carbon or finite sized graphite structure due to the ion impact. We suggest that high-energy ion irradiation can be useful for the modification of MWCNT structures.