Role of extrinsic atoms on the morphology and field emission properties of carbon nanotubes

Abstract

Extrinsic atoms were doped into multiwalled carbon nanotubes (MWCNTs) using microwave plasma-enhanced chemical vapor deposition. Doped nitrogen atoms alter the original parallel graphenes into highly curved ones including some fullerene-like structures. Doped nitrogen atoms could replace carbon atoms in MWCNTs and therefore increase the electronic density that enhances the electron field emission properties. On the other hand, the incorporation of boron into the carbon network apparently increases the concentration of electron holes that become electron traps and eventually impedes the electron field emission properties. Fowler-Nordheim plots show two different slopes in the curve, indicating that the mechanism of field emission is changed from low to high bias voltages. beta values could be increased by an amount of 42% under low bias voltages and 60% under high bias voltages in the N-doped MWCNTs, but decreased by an amount of 8% under low bias region and 68% under high bias voltage in the B-doped MWCNTs. (C) 2003 American Institute of Physics

Cathodoluminescence and electron field emission of boron-doped a-C:N films

“…Table 1 lists the field emission properties of the a-C:N and a-C:N:B films. A higher field is required to emit electrons from a-C:N:B film for the following reasons: (1) Degree of graphitization: The field emission characteristics can be [31]. Both generation of holes and recombination effect can decrease emission current, thereby leading to a higher threshold field (5.2 V/lm).…”

Carbon Nanotube‐Supported Catalysts for the Direct Methanol Fuel Cell

“…The proportion of nitrogen in CNTs is approximately 8%, as revealed by EDX. Addition of N 2 to the process gas is believed to promote the formation of a bamboo-like structure having a surface with a small radius of curvature [101][102][103]. Moreover, the incorporation of nitrogen atoms into graphene sheets with a bamboo-like structure favors the formation of pentagons and heptagons, and increases the reactivity of the neighboring carbon atoms, yielding the decorated nanotubes.…”

First-principles investigation on the field emission properties of B-doped carbon nanotubes

“…The change in the electronic structures can modify the field emission properties significantly. Thus, the control of the electronic structures of CNTs is of great technological importance, and the adsorption [6][7][8] and doping [9,10] of extrinsic atoms or molecules are the best way to accomplish this goal. With the development of the synthesis techniques, various kinds of doped CNTs have been fabricated [11].…”

“…N-and B-doped CNTs have been successfully synthesized using different techniques [13,14]. The existing experimental investigations indicate that N-doped CNTs show an enhanced electron field emission and special emission properties [9,[15][16][17] when compared with pristine CNTs. On the other hand, the experimental results, reported by Charlier et al [18], demonstrate that B-doped CNTs exhibit a stable electron field emission at lower turn-on voltage.…”

“…On the other hand, the experimental results, reported by Charlier et al [18], demonstrate that B-doped CNTs exhibit a stable electron field emission at lower turn-on voltage. However, Chan et al [9] have experimentally found that the incorporation of boron into CNT eventually impedes the electron field emission properties. Due to the existing contradicted experimental results, it is therefore of great interest to theoretically investigate how the doping of boron atom can affect the field emission properties of CNTs.…”