Field emission from the composite structure of vertical single-walled carbon nanotubes/ carbon nanocones

[[abstract]]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 ∼200 nm in height, and their diameters are ∼100 nm near the bottom and ∼10 nm at the top. The nanoscale Co particles ∼10 nm in diameter act as catalysts which favour the growth of VA-SWCNTs out of CNCs at 850 ◦C in the gravity-assisted CVD process. The average length and the growth time of VA-SWCNTs are ∼150 nm and 1.5 min, equivalent to a growth rate of ∼6 μm 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 μm−1 and the emission current density at the electric field of 5 V μm−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.[[fileno]]2010137010042[[department]]物理