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The ageing effect on the field emission (FE) reproducibility of multiwalleded carbon nanotubes (MWCNTs) synthesised by plasma enhanced chemical vapour deposition was investigated by scanning electron microscopy. To investigate the ageing effect on the physical state of the MWCNTs, a scanning electron microscope (SEM), a Raman spectrometer, an X-ray photoelectron spectroscope and an X-ray diffractometer were used to characterise the MWCNTs comprehensively before and after the ageing. Through ageing, the FE reproducibility became better because the larger number and more evenly distributed shorter MWCNTs - (resulted from the local vacuum breakdown of higher MWCNTs due to Joule heating and oxidisation) - became the dominating emitters. [ABSTRACT FROM AUTHOR]

The properties of the field emission (FE) from multi-walled carbon nanotubes (CNTs) in air used to generate the microplasma at near-atmospheric pressure were investigated in a removable gas cell built into a scanning electron microscope. The gaps between the electrodes were adjusted from 5 to 100 μm and the pressure was changed from 0 to 100 kPa. The obtained results have shown that the FE properties of the CNTs at 10 kPa and lower pressures were the same as those in vacuum. At a pressure more than 10 kPa, the FE threshold voltage in air was higher than those in vacuum, and increased with increasing atmospheric pressure. When the FE threshold voltage became higher than that of the gas breakdown, the microplasma was ignited before the FE initiation. Thus, the FE properties of the CNTs in air were stable when the FE potential was lower than the voltage of conventional gas discharge with CNT cathode. [ABSTRACT FROM AUTHOR]

Microplasma was produced in argon gas in a scanning electron microscope at near-atmospheric pressure using a multi-wall carbon nanotube (CNT) film as a cathode. It is demonstrated that with the CNT film used as a cathode, the breakdown voltage was much lower than the breakdown voltage when the conventional cathode made of flat metal film was used and the discharge was highly reproducible. These features of the gas discharge are defined by the field emission from the CNT cathode. [ABSTRACT FROM AUTHOR]