Transport properties of field effect transistors with randomly networked single walled carbon nanotubes grown by plasma enhanced chemical vapour deposition

The transport properties of randomly networked single walled carbon nanotube (SWNT) transistors with different channel lengths of L_c = 2-10 νm were investigated. Randomly networked SWNTs were directly grown for the two different densities of ρ ∼ 25 νm^-2 and ρ ∼ 50 νm^-2 by water plasma enhanced chemical vapour deposition. The field effect transport is governed mainly by formation of the current paths that is related to the nanotube density. On the other hand, the off-state conductivity deviates from linear dependence for both nanotube density and channel length. The field effect mobility of holes is estimated as 4-13 cm ² V^-1 s^-1 for the nanotube transistors based on the simple MOS theory. The mobility is increased for the higher density without meaningful dependence on the channel lengths.