Large area synthesis of conical carbon nanotube arrays on graphite and tungsten foil substrates

Thermionic emission properties of novel carbon nanostructures.

“…It was shown that CCNTs have high aspect ratio and excellent field enhancement factors in addition to sparse distribution, reducing the screening effect [69]. The previously described structural differences of sample 6 in comparison with other CCNT samples (presence of microhorns) could be the reason for the higher observed value for work function.…”

“…Concentric graphene layers are deposited around MWNT during the subsequent synthesis [69]. The number of graphene layers is gradually reduced towards the tip, where MWNT is exposed, which allows us to apply a field penetration model for Electric field of such magnitude according to the proposed field penetration model for SWNT [24] will reduce the potential barrier by ~0.4 eV.…”

“…While it is a rough estimation and one must consider the fact that the CCNTs have an exposed MWNT at the tip, we argue that our results of thermionic emission are consistent with the model in which field penetration is the main contributor for lowering the potential barrier and reduction of the value of the effective work function. It is also important to note that low densities of the CCNTs make the screening effect negligible [69].…”

“…Studied CCNT samples were grown by microwave plasma assisted chemical More detailed experimental procedure of the growth and sample preparation has been described in detail elsewhere [69,70]. However, some changes during the growth process were introduced for this particular study for both samples grown on the Pt wire and graphite foil.…”

“…Here, we present a novel architecture consisting of diamond nanocrystals grown on the tips of conical carbon nanotube (CCNT) array [69,70] and the results of thermionic emission properties. CCNT backbone is expected to provide conducting pathways for diamond crystals.…”