Web Release Date: December 22,
Electronic Structure and Field Emission Properties of Double-Walled Carbon Nanotubes Synthesized by Hydrogen Arc Discharge
and
Department of Nano Science, Cheongju University, Cheongju, 360-764, Korea, School of Electrical Engineering, Korea University, Seoul 136-713, Korea, and Department of Chemistry, Korea University, Jochiwon 339-700, Korea
Received: August 27, 2007
In Final Form: October 11, 2007
Abstract:
We have synthesized high-purity double-walled carbon nanotubes (DWCNTs) by an arc-discharge method in
hydrogen ambient. The DWCNTs were synthesized using a mixture of Fe catalyst and FeS promoter. Without
FeS promoter, we only obtained single-walled carbon nanotubes (SWCNTs). The synthesized DWCNTs had
outer diameters in the range of 3.0-3.4 nm and an average interlayer distance of 0.38 nm between graphene
layers. The FeS promoter played a key role for the DWCNT growth. The DWCNTs indicated high electronic
density of states in the binding energy region between 3.88 and 13.23 eV below Fermi energy, indicating that
the DWCNTs had alot of delocalized graphite 
and /
electrons. For field emission properties, the typical
turn-on field of DWCNTs was about 3.0 V/
m at the emission current density of 0.1 A/cm2, and the emission
current density of DWCNTs was about 10 mA/cm2 at the applied field of 6.5 V/m. It is considered that the
higher current densities of DWCNTs were mainly attributed to the emitted delocalized graphite and /
state electrons of DWCNTs. Moreover, DWCNTs have higher emission stability than SWCNTs due to two
neighboring graphene layers.
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