Field emission property of gradiently nitrogen-doped carbon nanotubes

Carbon nanotube (CNT) arrays, with diameter of 10-30 nm, doped with nitrogen were synthesized by thermal decomposition of xylene/pyridine/ferrocene at 800°C. SEM, TEM and Raman spectroscopy were used to characterize the as-produced sample. It is shown that the method produces a gradient of nitrogen concentration that modifies the CNTs from a hollow cylinder to a bamboo-shaped structure which contains a series of compartments whose lengths are gradually reduced as the nitrogen concentration increases. Field emission test on the as-grown nitrogen-doped CNTs suggests that they are good emitters with a turn-on and threshold field of 0.37 V/μm and 0.9 V/μm, respectively.