Etching Of Carbon Nanotubes Research Articles

Tailoring carbon nanotubes quickly into graphene nanoribbons along axis-direction via dynamic magnetic flux template

So far, the method of top-down preparing graphene nanoribbons by etching of carbon nanotubes (CNTs) mainly relies on the catalytic reaction of Fe, Co, and Ni nanoparticles. However, etching cannot be guaranteed along the CNT axis only. In this study, Ti3AlC2 is decomposed into liquid aluminum in the dynamic magnetic flux template to catalyze the growth of multiwalled carbon nanotubes (MWCNTs). Successively, the obtained MWCNTs are etched in-situ by rutile TiO2 particles to generate multilayered graphene nanoribbons (MLGNRs). Thus-obtained nanoribbons will create zigzag edges full of short-range order segment, demonstrating a spin glass state. This work has paved a new way for a top-down approach to create MLGNRs by tailoring MWCNTs along axis direction only using dynamic magnetic flux template.

Simultaneous production of aromatics-rich bio-oil and carbon nanomaterials from catalytic co-pyrolysis of biomass/plastic wastes and in-line catalytic upgrading of pyrolysis gas

An integrated process that includes catalytic co-pyrolysis of biomass/plastic wastes and in-line catalytic upgrading of pyrolysis gas were conducted to simultaneously produce aromatics-rich bio-oil and carbon nanotubes (CNTs). The influences of feedstocks blending ratio on the characteristics of bio-oil and CNTs were established. The reaction mechanism of carbon deposition during the system was also probed. The results showed that co-feeding plastic to biomass siginificantly enhanced the selectivity of monoaromatics (benzene, toluene, and xylene) from 5.6% for pure biomass to the maximum yield of 44.4% for 75.0% plastic ratio, and decreased naphthalene and its derivates from 85.9 to 41.7% correspondingly. The most synergistic effect on BTX selectivity occurred at 25% of plastic ratio. The multi-walled CNTs were successfully synethsized on Ni catalyst by utilizing prolysis gas as feedstocks. For pure biomass, the least CNTs yield with ultrafine diameters of 3.9–8.5 nm was generated via disproportionation reaction of CO which was derived from decarboxylation and decarbonylation of oxygenates on the ZSM-5 acid sites. With the rise of plastic ratio, sufficient hydrocarbons were produced for CNTs growth, endowing CNTs with long and straight tube walls, along with uniform diameters (~16 nm). The CNTs yield increased as high as 139 mg/g-cata. In addition, the decreased CO2 inhibited dry reforming with C1-C4 hydrocarbons and deposited carbon, avoiding excessive etching of CNTs. Thereby, high-purity CNTs with less defects were fabricated when plastic ratio was beyond 50% in the feedstock. The strategy is expected to improve the sustainability and economic viability of biomass pyrolysis.

A Self-Assembled Graphene Ribbon Device on SiC

Graphene ribbons, which may be fabricated by a wide variety of experimental techniques such as chemical processing, unzipping or etching of carbon nanotubes, molecular precursors, ion implantation, and so on, can find promising applications in interconnects, terahertz sensors, and plasmonic devices. Here we report measurements on self-assembled graphene ribbons that are prepared by a controlled high-temperature sublimation technique. The epitaxial graphene ribbons on SiC can be readily and efficiently located by confocal laser scanning microscopy for device fabrication using a removable metal protection layer to avoid contamination of the graphene and hexagonal boron nitride to serve as a top-gate dielectric spacer. These self-assembled graphene ribbons have smooth edges, and the observation of a magnetoresistance side peak in such a structure is consistent with diffusive boundary scattering in the quasi-ballistic regime. In contrast, graphene ribbons defined by electron-beam lithography and subsequent conventional reactive ion etching on the same SiC wafer only show pronounced negative magnetoresistance due to strong disorder in the edge structures (chemical dopants, the resolution of electron-beam lithography, etc.). Our experimental approaches are applicable to wafer-scale, graphene-based integrated circuits.

Ultrananocrystalline diamond decoration on to the single wall carbon nano tubes

We have demonstrated the decoration of the ultrananocrystalline diamonds on single walled carbon nanotubes using a hot filament assisted chemical vapor deposition. Study reveals the critical influence of the filament to substrate distance on the formation of ultrananocrystalline diamonds on to the single walled carbon nanotubes. It is also observed that etching of carbon nanotubes, due to the presence of unavoidable atomic hydrogen throughout the chemical vapor deposition processes, can be significantly reduced by adjusting the filament to substrate distance. Morphological and structural investigations performed using high resolution transmission electron microscope suggests the growth of ultrananocrystalline diamond is subsequent to the formation of crystalline sp2 carbon layer on the nanotube wall, enabling us to suggest a growth model. The composite synthesized can be thought not only to use as a fuel cell catalyst support but also as chemical sensors, bio-sensors and micro electromechanical systems (MEMS).

63.2: Field Emission Display with Homogenized Carbon Nanotube Emitters Grown by Resist‐Assisted Patterning Process

AbstractField emission display (FED) was fabricated with resist‐assisted patterning (RAP) process grown carbon nanotube (CNT) emitters. Electron emission current uniformity was strongly improved by homogenizing process with silicon‐on glass (SOG). The length of CNT emitters was homogenized with SOG coating and selective CNT etching process. Uniform CNT emitters were fabricated with the post‐growth homogenizing process. We fabricated 3 inch FED display with 32 μm sub‐pixel size with the CNT emitters. Electron emission current shows possible operation of the FED with 5 V/μm gate field. The electron emission characteristics and display performance were discussed.

Visualization and functions of surface defects on carbon nanotubes created by catalytic etching

Surface defects were created on carbon nanotubes (CNTs) by catalytic steam gasification or catalytic etching with iron as catalysts. The structure and morphology of the etched CNTs were studied by transmission electron microscopy (TEM) and scanning tunneling microscopy (STM). The electronic structure of the etched CNTs was investigated by ultraviolet photoelectron spectroscopy (UPS). The etched CNTs were treated by nitric acid to obtain oxygen-containing functional groups. The amount and the thermal stability of these groups were studied by temperature-resolved X-ray photoelectron spectroscopy (XPS). Temperature-programmed desorption with ammonia as a probe molecule (NH 3-TPD) was employed to investigate the interaction of the surface defects with foreign molecules in gas phase. TEM and STM studies disclosed the presence of surface defects especially edge planes on the etched CNTs. Etching of CNTs led to a less pronounced p-π band than the as-is CNTs, as evidenced by UPS studies. The XPS and NH 3-TPD studies demonstrated that the defects on the CNTs enhanced the reactivity of the exposed surfaces allowing obtaining a higher degree of oxygen functionalization and more active adsorption sites.

Growth Promotion and Etching of Carbon Nanotubes by Carbon Dioxide in Chemical Vapor Deposition using Methane Gas

ABSTRACTWe report the effect of CO2 addition to CO4 gas on carbon nanotube (CNT) growth by chemical vapor deposition. CO2 gas was introduced during the growth of CNTs on Fe0.05Mo0.025MgO0.925 and Ni0.05Mo0.025MgO0.925 catalysts by CO4 gas at a temperature of 800–850°C, and its concentration in a fraction of the gas flow rate was varied from 5×10−3 to 50%. In the experimental condition of the preferential growth of multi-walled CNTs, the carbon yield and the G/D ratio in the Raman spectra of the CNTs grown in 10%-CO2/CO4 were slightly higher than that grown in CO4 only. However, CNTs hardly grew when the CO2 concentration was more than 10%. We then prepared CO2 gas diluted with Ar gas (CO2/Ar) and varied its flow rate between 0 and 10 sccm. As the CO2/Ar gas flow rate was increased, the number of RBM peaks decreased even though the G/D ratio gradually decreased. The decrease in the RBM intensities of CNTs on the FeMoMgO catalyst was more significant than that of NiMoMgO.

Fabrication of aligned convex CNT field emission triode by MPCVD

In this work, vertically aligned carbon nanotubes (CNTs) were used to form a gated microcathode with a convex surface profile, being selectively synthesized from Microwave Plasma Chemical Vapor Deposition (MPCVD) with nickel (Ni) as a catalyst. A single-mask microfabrication process achieved an array of 10 μm × 10 μm CNT microtriodes with self-aligned gate. The convex profile is important in preventing cathode-gate leakage without resorting to more complicated fabrication processes or utilizing a gate over-etching approach. The main mechanism for the formation of the convex-shaped CNT microcathodes was investigated and is proposed to be the result of plasma etching of CNTs near the gate opening region due to higher plasma density during the growth process, leading to slower growth rate or shorter CNTs at the circumferential area. Additionally, previous simulation work has predicted that this type of surface profile is beneficial for more quasi-uniform electric field distribution on CNT tips. Field emission characteristics of the triode device were investigated, whereby a gate turn-on voltage as low as 25 V was achieved. The low turn-on of the device is mainly due to the smaller gate aperture made possible by the convex-shaped CNT microcathodes.

Etching of Carbon Nanotubes by OzoneA Surface Area Study

The oxidative etching of single walled carbon nanotubes (SWNTs) is useful for opening the end caps and the sidewalls of the nanotubes to provide access to the interior. We have studied the effect of successive treatment of SWNTs by 95% pure O(3)(g), which is a powerful and convenient oxidizing agent. The surface area of the SWNTs was measured following exposure to O(3)(g) at 300 K and also following heating to 1073 K in a vacuum to decompose the oxidized groups on the nanotubes, a procedure called etching. This O(3)-induced etching process was observed by scanning electron microscopy and by transmission electron microscopy, and the kinetics of the process was studied gravimetrically. It was found that O(3) attack occurs preferentially on the outermost geometric surface of the conglomerate sample of the nanotubes as a result of the high efficiency of O(3) to react in a few collisions with the nanotube surface. Ozone-induced etching causes the loss of pores in the 20 A diameter range as observed by nitrogen adsorption at equilibrium by density functional theory analysis.

Electrochemical behaviors and hydration properties of multi-wall carbon nanotube coated electrodes in water

Vertically aligned and randomly oriented multi-wall carbon nanotube coated silicon substrates were used as electrochemical electrodes. The effects of anodization processes and cathodic treatments in deionized water on carbon nanotubes were studied by means of DC experiments as well as cyclic voltammetric (CV) measurements. Anodization processes modified as-grown and hydrophobic carbon nanotubes and converted them to become hydrophilic. Cathodic processes caused etching of carbon nanotubes. The etching products made originally clear water change into black water. The black etching products left on top of carbon nanotubes after water vaporized made the carbon nanotube coated electrode less hydrophobic than that of as-grown carbon nanotubes but also less hydrophilic than that of anodized carbon nanotubes.

In situ growing and etching of carbon nanotubes on silicon under microwave plasma

In situ growing and etching of carbon nanotubes on silicon under microwave plasma