Diamond-graphite nanorods produced by microwave plasma chemical vapor deposition (original) (raw)
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Diamond-graphite nanorods produced by microwave plasma chemi
One dimensional C-C nanostructure, diamond-graphite nanorods, was synthesized by the argon rich microwave plasma chemical vapor deposition method. The nanostructures were characterized by scanning electron microscopy and transmission electron microscopy techniques. The diamond nanorods (DNRs) consist of single-crystalline diamond cores of 2-5 nm in diameter and several tens of nanometer in length. The DNRs are encapsulated in a graphitic shell of variable thickness. Raman and X-ray diffraction spectra also indicated the coexistence of diamond and graphite phases in the film. The addition of nitrogen is considered to be helpful for the highly efficient formation of graphite shell. The high content of methane in the gas mixture in the presence of argon rich environment is suggested to be responsible for the one dimensional growth. (C) 2009 Elsevier B.V. All rights reserved.
Hybrid Diamond-Graphite Nanowires Produced by Microwave Plasma Chemical Vapor Deposition
Advanced Materials, 2007
Over the last ten years, one dimensional structures, carbon nanotubes (CNTs) and carbon nanofibers, have received great attention since they are considered to be one of the main components in future nanotechnologies, in particular in the engineering of nanoscale devices. Hybrid structures of CNT with other nanocarbons such as fullerenes, carbon onions or nanodiamond can further extend the diversity of building units for the design of actuators, field electron emitters, novel composites and other applications. While the production of CNT and other sp 2 -bonded nanocarbons has been successfully realized by a variety of techniques, the synthesis of diamond nanowires (nanorods) of nanometer diameters -the one-dimensional sp 3 -configured analogue of CNT -turned out to be much more difficult. Using ab initio calculations, the fundamental stability of diamond nanowires (DNW) was explored depending on size and crystallographic direction, and this object was predicted to be stable (energetically favored) at diameters ranging from 2.7 nm to 9 nm. Another prediction was the instability of dehydrogenated (111) surfaces of one-dimensional nanodiamond, leading to the formation of hybrid nanorods, i.e., DNW covered by a graphitic shell, called "bucky wires". It is remarkable that hybrid nanograins called "bucky-diamond" were produced more than ten years ago, whereas the "bucky-wires" never have been observed experimentally. The DNW are expected to possess unique mechanical and electronic properties, in particular: the predicted brittle fracture force and zero strain stiffness for DNW with radii greater than about 1-3 nm exceed those for CNT. The elec-tronic structure of DNW has been theoretically considered by Barnard et al.; they find that the band gap of diamond nanowires is narrower than that of bulk diamond, moreover it varies with the surface morphology, diameter and the orientation of the principle axis.
Diamond nanorods (DNRs) synthesised by the high methane content in argon rich microwave plasma chemical vapour deposition (MPCVD) have been implanted with nitrogen ions. The nanorods were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The DNRs consist of single-crystalline diamond cores of 3-5 nm in diameter and several tens of nanometres in length. For purification from non-diamond contents, hydrogen plasma etching of DNRs was performed. Structural modifications of etched DNRs were studied after irradiating with 50 keV nitrogen ions under the fluence of 5 x 10(14), 1 x 10(15), 5 x 10(15) and 1 x 10(16) ions cm(-2). Nitrogen-ion implantation changes the carbon-carbon bonding and structural state of the nanocrystalline diamond (NCD). Raman spectroscopy was used to study the structure before and after ion irradiation, indicating the coexistence of diamond and graphite in the samples. The results indicated the increase in graphitic and sp(2)-related content, at the expense of decrease in diamond crystallinity, for ion implantation dose of 5 x 10(15) cm(-2) and higher. The method proves valuable for the formation of hybrid nanostructures with controlled fractions of sp(3)-sp(2) bonding.
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Diamond Deposition on Graphite in Hydrogen Microwave Plasma
Journal of Coating Science and Technology, 2018
Hydrogen plasma etching of graphite generates radicals that can be used for diamond synthesis by chemical vapor deposition (CVD). We studied the etching of polycrystalline graphite by a hydrogen microwave plasma, growth of diamond particles of the non-seeded graphite substrates, and characterized the diamond morphology, grain size distribution, growth rate, and phase purity. The graphite substrates served simultaneously as a carbon source, this being the specific feature of the process. A disorder of the graphite surface structure reduces as the result of the etching as revealed with Raman spectroscopy. The diamond growth rate of 3-5 µm/h was achieved, the quality of the produced diamond grains improving with growth time due to inherently nonstationary graphite etching process.
Synthesis of nanocrystalline diamonds by microwave plasma
Journal of Physics D: Applied Physics, 2007
Nanocrystalline diamonds, varying in size from 40 to 400 nm, with random faceting were grown without the help of initial nucleation sites on nickel substrates as seen by scanning electron micrographs. These carbonaceous films were deposited in a microwave plasma reactor using hexane/nitrogen based chemical vapour deposition. The substrate temperatures during deposition were varied from 400 to 600 • C. The morphological investigations obtained by scanning electron micrographs and atomic force microscopy revealed the presence of nanocrystallites with multifaceted structures. Micro Raman investigations were carried out on the deposited films, which conclusively inferred that the growth of nanodiamond crystallites seen in the scanning electron micrographs correlate with clear Raman peaks appearing at 1120 and 1140 cm −1 . Nanoindentation analysis with atomic force microscopy has revealed that the carbonaceous deposition identified by the Raman line at ∼1140 cm −1 , in fact, is related to nanodiamond on account of its hardness which was ∼30 GPa. X-ray diffraction data supported this fact.
Diamond nanorods from nanocrystalline diamond films
Journal of Crystal Growth, 2009
Diamond nanorods (DNRs) have been prepared by hydrogen plasma post-treatment of nanocrystalline diamond films in radio-frequency (RF) plasma-assisted hot-filament chemical vapor deposition. Singlecrystal diamond nanorods with diameters of 3-5 nm and with lengths up to 200 nm grow under hydrogen plasma irradiation of nanocrystalline diamond thin film on the Si substrate at high temperatures. The DNRs growth occurs from graphite clusters. The graphite clusters arises from the etching of diamond carbon atoms and from the non-diamond phase present in the parent film. The graphite clusters recrystallized to form nanocrystalline diamonds which further grow for diamond nanorods. The negative applied bias and surface stresses are suggested to support one-dimensional growth. The growth direction of diamond nanorods is perpendicular to the (111) crystallographic planes of diamond. The studies address the structure and growth mechanism of diamond nanorods.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1992
Hard a-C:H films were grown in a dual frequency plasma sustained simultaneously by microwave and radio-frequency power. "Optimum" growth conditions, namely those leading to the most pronounced sp3 structural features in the films, depend very strongly on the methane feed gas flow rate and on the argon concentration, in the case of CH 4 / Ar mixtures. These optimum conditions have been found to correspond to maximum values of ion flux at the growing film surface, and high concentrations of precursor species such as CH, C2> C 3 , and atomic hydrogen in the plasma, as revealed by optical emission spectroscopy. Films grown under optimum conditions have very high microhardness (~50 GPa), high density (1.8 g/cm-3), and low internal stress (0.5 GPa). Addition of argon to the methane is shown to enhance the gas phase fragmentation and to raise the microhardness, but argon atoms trapped in the films' structure increase the internal stress.