Density control of carbon nanowalls grown by CH4/H2 plasma and their electrical properties (original) (raw)
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Journal of Nanomaterials
In this study, we investigated the morphological, structural, and electrical properties of carbon nanowall (CNW) structures obtained by plasma-enhanced chemical vapour deposition (PECVD) and underlined the induced effects of argon/nitrogen (Ar/N2) postsynthesis plasma treatment on the electrical behaviour. The top view and cross-section scanning electron microscopy micrographs revealed that the fabricated samples are about 18 μm height, and the edges are less than 10 nm. The Raman analysis showed the presence of the specific peaks of graphene-based materials, i.e., D-band, G-band, D′-band, 2D-band, and D+G-band. The average values of the electrical resistance of fabricated samples were evaluated by current-voltage characteristics acquired at room temperature, in the ranges of 0 V–0.2 V, and an increase was noticed with about 50% after the Ar/N2 postsynthesis plasma treatment compared to pristine samples. Moreover, the Hall measurements proved that the obtained CNW structures had p-t...
Applied Physics Letters, 2004
Two-dimensional carbon nanostructures ͑carbon nanowalls͒ were fabricated using capacitively coupled radio-frequency plasma-enhanced chemical vapor deposition assisted by H radical injection. Carbon nanowalls were grown on Si, SiO 2 , and sapphire substrates without catalyst, and independent of substrate materials. Correlation between carbon nanowall growth and fabrication conditions, such as carbon source gases was investigated. In the case using C 2 F 6 /H 2 system, aligned carbon nanowalls were grown vertically on the substrate, while carbon nanowalls grown using CH 4 /H 2 system were waved and thin ͑Ͻ10 nm͒. In the case of the deposition without H radical injection, on the other hand, carbon nanowalls were not fabricated.
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DC discharge plasma studies for nanostructured carbon CVD
Diamond and Related Materials, 2003
A synthesis of carbon films by d.c. discharge plasma-enhanced chemical vapor deposition using a hydrogen-methane gas mixture was investigated by optical emission spectroscopy and by measurements of current-voltage dependencies. The effects of gas composition and pressure on the characteristics of d.c. discharge in the methane-hydrogen gas mixture are studied. Variation of the deposition process parameters over a wide range allows us to obtain various carbon thin film materials, whose structure and composition were qualitatively characterized by Raman spectroscopy and electron microscopy. The data of optical emission spectroscopy show the presence in the discharge plasma of H, H , CH and C activated species, which play a decisive role in 2 2 nanostructured graphite-like carbon film formation and carbon condensation in the gas phase. We propose a model for the formation of graphitic nanostructured carbon films in plasma containing C dimers. 2
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Physical chemistry chemical physics : PCCP, 2014
In this paper we propose a new and simple method to tune the carbon nanowall microstructure by sharp variation of CH4/H2 plasma conditions. Using theoretical calculations we demonstrated that the sharp variation of gas pressure and discharge current leads to significant variation of plasma radical composition. In some cases such perturbation creates the necessary conditions for the nucleation of smaller secondary nanowalls on the surface of primary ones.
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The effect of plasma parameters on the nanostructures formed during physical vapor deposition growth of carbon films has been studied. It was shown that the formation and nature of nanostructures strongly depend on plasma density and ion energy during the deposition. High plasma density results in formation of nanocrystals with preferred orientation even at low negative substrate bias (300 V) while at low plasma density higher substrate bias (500 V) is required for the nanocrystals. Moreover, at the same plasma density the nature of the nanostructures strongly depends on the ion energy. At higher ion energies, carbon nanotubes are formed in the microstructure while at lower ion energies, graphitic nanostructures are more stable. It was also found that prior to the formation of preferred orientation, an amorphous layer is formed at the silicon/carbon interface. Through electron energy loss spectroscopy, it is shown that the structure of this layer strongly depends on ion energy during the deposition.
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Microelectronic Engineering, 2003
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Journal of Applied Physics, 2004
The results of numerical simulations, optical emission spectroscopy ͑OES͒, and quadrupole mass spectrometry ͑QMS͒ of inductively coupled Ar/CH 4 /H 2 plasmas in the plasma enhanced chemical vapor deposition ͑PECVD͒ of self-assembled vertically aligned carbon nanostructures ͑CNs͒ are presented. A spatially averaged ͑global͒ discharge model is developed to study the densities and fluxes of the radical neutrals and charged species, the effective electron temperature, methane conversion factor under various growth conditions. The numerical results show a remarkable agreement with the OES and QMS data. It is found that the deposited cation fluxes in the PECVD of CNs generally exceed those of the radical neutrals.
The electronic structure of carbon films deposited in rf argon–hydrogen plasma
Journal of Electron Spectroscopy and Related Phenomena, 2006
The electronic structure of C films deposited by sputtering a graphite target in rf. Ar-H 2 plasma is investigated by photoemission, Auger emission and electron energy loss spectroscopy (EELS) as a function of the H 2 concentration in the feed gas, referred to as [H 2 ]. Adding hydrogen to the plasma causes the films to change from a graphite-like unhydrogenated structure to a non-graphitic hydrogenated structure. The film mass density, as derived from the + plasmon energy, decreases upon H 2 addition to the gas mixture, goes through a minimum at low [H 2 ] and increases with increasing [H 2 ]. It reveals a non-monotonous behavior of the film H content as a function of [H 2 ], the maximum H incorporation occurring at low [H 2 ]. This appears to be a characteristic of C deposition via graphite sputtering in Ar-H 2 plasma and it is discussed in connection with previous results on the subject.
PECVD of Carbon Nanostructures in Hydrocarbon-Based RF Plasmas
Contributions to Plasma Physics, 2005
Different aspects of the plasma-enhanced chemical vapor deposition of various carbon nanostructures in the ionized gas phase of high-density, low-temperature reactive plasmas of Ar+H2+CH4 gas mixtures are studied. The growth techniques, surface morphologies, densities and fluxes of major reactive species in the discharge, and effects of the transport of the plasma-grown nanoparticles through the near-substrate plasma sheath are examined. Possible growth precursors of the carbon nanostructures are also discussed. In particular, the experimental and numerical results indicate that it is likely that the aligned carbon nanotip structures are predominantly grown by the molecular and radical units, whereas the plasma-grown nanoparticles are crucial components of polymorphous carbon films.