Electronic Structure and Field Emission Properties of Double-Walled Carbon Nanotubes Synthesized by Hydrogen Arc Discharge

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 σ and σ/π electrons. For field emission properties, the typical turn-on field of DWCNTs was about 3.0 V/μm at the emission current density of 0.1 μA/cm2, and the emission current density of DWCNTs was about 10 mA/cm2 at the applied field of 6.5 V/μm. It is considered that the higher current densities of DWCNTs were mainly attributed to the emitted delocalized graphite σ and σ/π state electrons of DWCNTs. Moreover, DWCNTs have higher emission stability than SWCNTs due to two neighboring graphene layers.

Is It Possible to Dope Single‐Walled Carbon Nanotubes and Graphene with Sulfur?

“…The strong dependence observed between the presence of sulfur and the growth of DWCNTs was attributed to modification of the kinetics rather than energetics, since the growth of DWCNTs is supposed to be energetically more costly. Recently, Ha et al [4] confirmed the results obtained by Ci and co-workers: [3] DWCNTs were obtained if Fe was used as catalyst and FeS as promoter, but only SWCNTs were produced when FeS was absent. Neither investigation [3,4] reported the presence of sulfur atoms in the CNT walls.…”

A Reliable Field Emission Performance of Double-Walled Carbon Nanotube Field Emitters

“…4, the DWCNT field emitters showed a slight degradation after 25 hrs, indicating a very stable field emission. Compared with the previously reported emission stability of the SWCNTs, the emission stability of the DWCNTs was much better than that of the SWCNTs [30]. We believe that the stable emission properties were caused by two graphene layers and good crystallinity.…”

“…In fact, this turn-on field was a little lower than that of arc-SWCNTs [35]. Recently, there have been some reports on the field emission properties of the DWCNTs.…”

Field Emission of Single‐Layer Graphene Films Prepared by Electrophoretic Deposition

“…The E to value of graphene films is also lower than that of free-standing sub-nanometer graphite sheets (E to, 4.7 V mm À1 ) synthesized by PECVD, [19] and the E to and E thr values are well comparable to those of CNT films fabricated by EPD (E to , 1.4-3.0 V mm À1 ) [28,29,40,41] and screen-printing (E to , 2-6.4 V mm À1 ) techniques. [42] The Fowler-Nordheim (F-N) theory is the most-commonly used model for understanding the electron emission from a metal surface under a strong applied field, and it has been also widely used to investigate the electron-emission behavior of various nanostructures, such as CNTs, [3][4][5][43][44][45] nanowires, [46] and nanowalls. [47] To elucidate the electron-emission mechanism and the differences in the field-emission behaviors of graphene-powder coating and graphene film, we plotted ln (J/E 2 ) versus 1/E, which yields a line, in good agreement with the F-N equation (Fig.…”