Structure changes of MPECVD-grown carbon nanosheets under high-temperature treatment (original) (raw)
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Carbon nanosheets by microwave plasma enhanced chemical vapor deposition in CH4–Ar system
Applied Surface Science, 2011
We employ a new gas mixture of CH 4-Ar to fabricate carbon nanosheets by microwave plasma enhanced chemical vapor deposition at the growth temperature of less than 500 • C. The catalyst-free nanosheets possess flower-like structures with a large amount of sharp edges, which consist of a few layers of graphene sheets according to the observation by transmission electron microscopy. These high-quality carbon nanosheets demonstrated a faster electron transfer between the electrolyte and the nanosheet surface, due to their edge defects and graphene structures.
Plasmonics, 2011
High-quality, free-standing, and vertically interconnected three-dimensional (3-D) graphitic nanosheets (GNSs) were synthesized over the surface of hemispherical carbon particles/GaN at 700 °C by microwave plasma chemical vapor deposition (CVD) in presence of methane gas, whereas the hemispherical carbon particles have been directly deposited on GaN/sapphire template. The GNSs are ∼1–5 nm in thickness and have a graphitic flake structure on hemispherical carbon particles. The vertically interconnected 3-D GNSs on hemispherical carbon particles have been characterized by scanning electron microscopy, transmission electron microscopy, selective area electron diffraction pattern, X-ray diffraction, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and nitrogen gas adsorption-Brunauer-Emmet-Teller. The present CVD approach is capable of producing large quantities of GNSs with high purity. Moreover, a high-purity free-standing and vertically interconnected 3-D GNSs on hemispherical carbon particles have an enormous potential for applications in electronic devices, biological sensors, gas uptake and storage, fuel cells, lithium ion batteries, and more.
A mechanism for carbon nanosheet formation
Carbon, 2007
The growth, structure and properties of a two-dimensional carbon nanostructure-carbon nanosheet produced by radio frequency plasma enhanced chemical vapor deposition have been investigated. The effects of deposition parameters on the structure and properties of carbon nanosheets were also investigated. A growth model has been described proposing that atomically thin graphene sheets result from a balance between deposition through surface diffusion and etching by atomic hydrogen, and that the observed vertical orientation of these sheets results from the interaction of the plasma electric field with their anisotropic polarizability.
Carbon, 2014
Vertically aligned carbon nanosheets (CNSs) with bi-and trilayer graphene have been achieved on various metal substrates from solid carbon sources by irradiation with H 2 and Ar plasma. The resulting graphene structures have fewer layers, bigger sizes, and higher graphitization compared to previous reports obtained from gas sources, as confirmed by scanning and transmission electron microscopes, Raman and X-ray photoelectron spectroscopes. The results suggest that the interaction between the plasma (of H 2 and Ar) and carbon sources favors the formation of bigger and thinner nucleation cites in the initial stage and atomic H etching dominates during the whole thinner CNS growth. The vertically aligned graphene film can be directly transferred on as-patterned SiO 2 /Si to form a heterojunction photovoltaic cell with a power conversion efficiency of 0.9%.
Carbon, 2004
An ultrathin sheet-like carbon nanostructure, carbon nanosheet, has been effectively synthesized with CH 4 diluted in H 2 by an inductively coupled radio-frequency plasma enhanced chemical vapor deposition. Nanosheets were obtained without catalyst over a wide range of deposition conditions and on a variety of substrates, including metals, semiconductors and insulators. Scanning electron microscopy shows that the sheet-like structures stand on edge on the substrate and have corrugated surfaces. The sheets are 1 nm or less in thickness and have a defective graphite structure. Raman spectra show typical carbon features with D and G peaks at 1350 and 1580 cm À1 , respectively. The intensity ratio of these two peaks, I(D)/I(G), increases with methane concentration or substrate temperature, indicating that the crystallinity of the nanosheets decreases. Infrared and thermal desorption spectroscopies reveal hydrogen incorporation into the carbon nanosheets.
Fullerenes, Nanotubes and Carbon Nanostructures, 2014
This paper reports the synthesis of nanostructure carbon (ns-carbon) films deposited by microwave plasma-enhanced chemical vapor deposition (MW PECVD) technique at low pressure and room temperature. ns-carbon films have been characterized by scanning electron microscopy, electron dispersive x-ray spectroscopic analysis, atomic force microscopy, Raman spectroscopy, X-ray diffraction, UV-visible spectroscopy and high-resolution transmission electron microscopy. The shape of nanostructure is changing from granular to sheet-like structure when the pressure increased from 55 to 110 mTorr.
Carbon nanostructures were obtained by acetylene injection into an argon plasma jet in the presence of hydrogen. The samples were synthesized in similar conditions, except that the substrate deposition temperatures were varied, ranging from 473 to 973 K. A strong dependence of morphology, structure, and graphitization upon was found. We obtained vertical aligned carbon nanotubes (VA-CNTs) at low temperatures as 473 K, amorphous carbon nanoparticles (CNPs) at temperatures from about 573 to 673 K, and carbon nanowalls (CNWs) at high temperatures from 773 to 973 K. Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to substantiate the differences in these material types. It is known that hydrogen concentration modifies strongly the properties of the materials. Different concentrations of hydrogen-bonded carbon could be identified in amorphous CNP, VA-CNT, and CNW. Also, the H : C ratios along depth were determined for the obtained materials.
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 Surface Science, 2012
Carbon nanosheets (CNSs) have been synthesized by electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) using a mixture of acetylene and argon gases on copper foil as the substrate. Micrometer-wide carbon sheets consisting of several atomic layers thick graphene sheets have been synthesized by controlled decomposition of carbon radicals in ECR-PECVD. Raman spectroscopy of these films revealed characteristics of a disordered graphitic sheet. Thick folded carbon-sheets and a semi transparent freestanding CNSs have been observed by scanning electron microscopy. This is a promising technique to synthesize free standing CNSs and can be used in the fabrication of nanoelecronic devices in future.