Vertically aligned multiwalled carbon nanotubes were grown on a tungsten (W) tip by thermal chemical vapor deposition (CVD), applying a negative biasing voltage to the W tip in a pin-plate electrodes configuration. The carbon nanotube(CNT) electrodes, due to their nano-sized tip radii, create very high electric fields, and reduce significantly the breakdown voltage. Comparing the CNTs-grown W tip electrode to the W tip electrode, the ignition voltage for the former case decreased from 230 V to 181 V, while the saturation current increased from 12 μA to 20 μA. These results are attributed to a relatively high field enhancement factor β~960 of the CNTs electrodes compared to β~60 for the simple W tip.There are also significant differences between the W tip electrodes with and without CNTs in the values of the igniting voltage and discharge current, when the W tips were used as cathode.. : 52.80.-s, 52.90.+z, 81.07.-b
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