We grew vertically aligned carbon nanotubes ͑CNTs͒ using microwave plasma-enhanced ͑MPE͒ and thermal chemical-vapor deposition ͑CVD͒ and characterized their field emission properties. We observe that the flickering and instability in the field emission are due to the metal particles present on the field-emission array ͑FEA͒ surface, particularly from the MPECVD-grown samples. The existence of metal particles is an obstacle to obtaining reliable emission properties. The emission properties of the CNT-FEA are studied as a function of gas-exposure time with hydrogen, nitrogen, and oxygen gases. Gas exposures affected turn-on voltage, hysteresis, and the slope of Fowler-Nordheim plots. We observe that the saturation of emission currents is attributed to gas adsorbates present on the surface of the FEA. Oxygen exposures induce more severe degradation on the field-emission properties than nitrogen, whereas emission properties are improved by hydrogen gas exposures that clean the surface of emitters. In addition, hydrogenation of carbon nanotubes has technical importance for activation of the CNT-FEA.

Field electron emission from carbon nanotubes grown by plasma-enhanced chemical vapor depositionField emission properties of 4.5 in. flat panel displays in a diode type panel using single-walled ͑SWNTs͒ and multiwalled carbon nanotube tips ͑MWNTs͒ were characterized and compared. The panel, fabricated by a slurry squeezing and surface rubbing technique, enables the generation of more emission sites by removing materials on the surface. The turn-on field of MWNTs decreased from 6.4 to 3 V/m by treatment of the surface, and that of SWNTs also decreased, from 4.5 to 2 V/m. The density of aligned MWNTs is approximately 2/m 2 , whereas the aligned SWNTs were uniformly distributed, with densities of 5-10/m 2 . As a result, SWNT films show higher emission uniformity than MWNT films. A gradual degradation over time was observed in both MWNTs and SWNTs. The current stability curve of the SWNTs decreased about 20%, while that of the MWNTs decreased less than 10%.