Abstract:Carbon nanotubeshave many advantages over conventional semiconductor and metal emitters for field emission displays (FEDs). However, the origin of the current saturation seen in carbon nanotubes at high fields is poorly understood. Here the effect of gas adsorbates on the field emission properties of patterned carbon nanotube arrays, such as the one shown in the Figure, is investigated.
“…2, 19 The LDOS of the openended tube, however, clearly reveals that p z orbitals are the main source of the LDOS peak at the Fermi level as shown in Fig. 4͑a͒.…”
We investigated the electronic structures of chemically modified carbon nanotube tips under electric fields using density functional calculations. Hydrogen, oxygen, and hydroxyl group-terminated nanotubes have been considered as field emitters or probe tips. In the case of the open-ended tubes, the field emission originates primarily from the dangling-bond states localized at the edge, whereas the pentagonal defects are the main source of the field emission in the capped tubes. The open-ended nanotube with a zigzag edge is an efficient field emitter because of the localized electronic states around the Fermi level and the atomic alignment of carbon-carbon bonds along with external electric fields. Tip functionalization alters the local density of states as well as the chemical selectivity of nanotubes in various ways. The correlations between atomic geometries of chemically functionalized tips and their electronic structures are further discussed. We propose that a hydrogen-terminated tube would be a promising probe tip for selective chemical imaging.
“…2, 19 The LDOS of the openended tube, however, clearly reveals that p z orbitals are the main source of the LDOS peak at the Fermi level as shown in Fig. 4͑a͒.…”
We investigated the electronic structures of chemically modified carbon nanotube tips under electric fields using density functional calculations. Hydrogen, oxygen, and hydroxyl group-terminated nanotubes have been considered as field emitters or probe tips. In the case of the open-ended tubes, the field emission originates primarily from the dangling-bond states localized at the edge, whereas the pentagonal defects are the main source of the field emission in the capped tubes. The open-ended nanotube with a zigzag edge is an efficient field emitter because of the localized electronic states around the Fermi level and the atomic alignment of carbon-carbon bonds along with external electric fields. Tip functionalization alters the local density of states as well as the chemical selectivity of nanotubes in various ways. The correlations between atomic geometries of chemically functionalized tips and their electronic structures are further discussed. We propose that a hydrogen-terminated tube would be a promising probe tip for selective chemical imaging.
“…Moreover, we consider the emission current stability (J/J i = 68.9% after 2 h) of the SN-a FWCNT-based field emitter to be the worst among the three samples. It is well known that the emission current of nanotubes decreases when a nanotube tip with attached residual oxygen gases is degraded by Joule heating under a high electric field [32]. In fact, the outgassing from the cathode is one of the main reasons for vacuum deterioration, resulting in degradation of the emission current.…”
Section: Field Emission Properties Of Fwcnts/teos Thin Film Field Emimentioning
We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/ TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.
“…The electron source exhibits good emission stability behaviors in wide pressure range. However, the current fluctuation increases to ±4.24 % in 2.59 × 10 −9 Torr vacuum, comparing with ±2.72 % in 2.48 × 10 −10 Torr, which is believed to be related to the gas adsorption, such as nitrogen and hydrogen [16, 28]. Fig.…”
The field emission properties and the vacuum measurement application are investigated from the multi-walled carbon nanotubes (MWNTs) grown directly on catalytic stainless steel substrates. The MWNT emitters present excellent emission properties after the acid treatment of the substrate. The MWNT gauge is able to work down to the extreme-high vacuum (XHV) range with linear measurement performance in wide range from 10−11 to 10−6 Torr. A modulating grid is attempted with improved gauge sensitivity. The extension of the lower pressure limit is attributed largely to low outgassing effect due to direct growth of MWNTs and justified design of the electron source.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1207-6) contains supplementary material, which is available to authorized users.
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