Field emission from a composite structure consisting of vertically aligned single-walled carbon nanotubes and carbon nanocones

摘要

Vertically aligned single-walled carbon nanotubes (VA-SWCNTs) have been fabricated on carbon nanocones (CNCs) in a gravity-assisted chemical vapour deposition (CVD) process. The CNCs with nanoscale Co particles at the top were first grown on the Co/Si(100) substrate biased at 350 V in a plasma enhanced chemical vapour deposition process. The CNCs typically are similar to 200 nm in height, and their diameters are similar to 100 nm near the bottom and similar to 10 nm at the top. The nanoscale Co particles similar to 10 nm in diameter act as catalysts which favour the growth of VA-SWCNTs out of CNCs at 850 degrees C in the gravity-assisted CVD process. The average length and the growth time of VA-SWCNTs are similar to 150 nm and 1.5 min, equivalent to a growth rate of similar to 6 mu m h(-1). The diameters of VA-SWCNTs are estimated to be 1.2-2.1 nm. When VA-SWCNTs are fabricated on CNCs, the turn-on voltage is reduced from 3.9 to 0.7 V mu m(-1) and the emission current density at the electric field of 5 V mu m(-1) is enhanced by a factor of more than 200. The composite VA-SWCNT/CNC structure is potentially an excellent field emitter. The emission stability of the VA-SWCNT/CNC field emitter is discussed.