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.

Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al 2 O 3 substrate by a simple physical vapor-deposition method at a low temperature of 450 °C. The diameter and growth rate of ZnO nanowires increased as a function of growth temperature. TEM observation showed that the ZnO nanowires were synthesized along the c-axial direction of the hexagonal crystal structure. We demonstrate that ZnO nanowires followed the self-catalyzed growth mechanism on the ZnO nuclei. Besides high-quality ZnO nanowires, sometimes a fascinating hierarchically ordered ZnO structure was also observed.

We have investigated nitrogen doping effects on the structure and crystallinity of bamboo-shaped multiwalled carbon nanotubes (BS-MWNTs) by means of x-ray photoemission spectroscopy (XPS) and transmission electron microscopy. By controlling the NH3/C2H2 flow ratio during the chemical vapor deposition, the nitrogen concentrations of 0.4% to 2.4% were obtained. According to the XPS measurements, the increasing nitrogen concentration gave rise to an increase of the N-sp3 C bonds as well as the deterioration of the crystallinity of the BS-MWNTs. Besides, the N-sp3 C bonds were found to prevail over the N-sp2 C bonds above 5% nitrogen concentration. At higher nitrogen concentrations, the BS-MWNTs showed shorter compartment distances, presumably due to the suppressed surface diffusion of carbon on the catalyst particles.

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We have synthesized high-quality gallium nitride ͑GaN͒ nanowires by a chemical-vapor-deposition method and studied the electrical transport properties. The electrical measurements on individual GaN nanowires show a pronounced n-type field effect due to nitrogen vacancies in the whole measured temperature ranges. The n-type gate response and the temperature dependence of the current-voltage characteristics could be understood by the band bending at the interface of the metal electrode and GaN wire. The estimated electron mobility from the gate modulation characteristics is about 2.15 cm 2 /V s at room temperature, suggesting the diffusive nature of electron transport in the nanowires.