Publications (10)14.37 Total impact
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Article: Single- and few-walled carbon nanotubes grown at temperatures as low as 450 degrees c: electrical and field emission characterization.
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ABSTRACT: Single-wall (SW-) and few-walled (FW-) carbon nanotubes (CNTs) were synthesized on aluminum/ cobalt coated silicon at temperatures as low as 450 degrees C by plasma enhanced chemical vapor deposition technique (PECVD). The SWCNTs and FWCNTs grow vertically oriented and well separated from each other. The cold field emission studies of as-grown SWCNTs and FWCNTs showed low turn-on field emission threshold voltages, strongly dependent of the nanotubes morphology. Current-voltage curves of individual CNTs, measured by conductive atomic force microscopy (CAFM), showed an electrical resistance of about 90 Komega, that is attributed mainly to the resistance of the contact between the CNTs and the conductive CAFM tip (Au and Pt).Journal of Nanoscience and Nanotechnology 10/2007; 7(9):3350-3. · 1.56 Impact Factor -
Article: Impact of the etching gas on vertically oriented single wall and few walled carbon nanotubes by plasma enhanced chemical vapor deposition
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ABSTRACT: Vertically oriented single wall nanotubes (SWNTs) and few walled nanotubes (FWNTs) have been grown by electronic cyclotron resonance plasma enhanced chemical vapor deposition (PECVD) on silica flat substrates. The impact of the plasma parameters on SWNT and FWNT growth has been investigated using two different etching gas mixtures, namely, C <sub>2</sub> H <sub>2</sub>/ N H <sub>3</sub> and C <sub>2</sub> H <sub>2</sub>/ H <sub>2</sub> with various ratios and applied bias voltages. Kinetic studies are also proposed in order to describe the FWNT growth mechanism by plasma techniques. A key role played by the reactive gas ( N H <sub>3</sub> and H <sub>2</sub> ) is observed in the PECVD process, contrary to multiwalled nanotube growth. It is demonstrated that the balance between FWNT growth versus FWNT etching can be widely modulated by varying the gas mixture and bias voltage. It is shown that the use of hydrogen for hydrocarbon gas dilution restricts the destruction of SWNT and FWNT by the plasma species (ions and radicals).Journal of Applied Physics 04/2007; · 2.17 Impact Factor -
Article: ERDA and structural characterization of oriented multiwalled carbon nanotubes
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ABSTRACT: Oriented multiwalled carbon nanotubes have been synthesized by distributed electron cyclotron resonance plasma enhanced chemical vapor deposition. Elastic recoil detection analysis measurements on multiwalled carbon nanotubes are reported here for the first time. On the basis of the recorded depth profiles, we have developed a simple model to estimate the surface densities of as-grown nanotubes. Besides, nitrogen and hydrogen contents into MWNT, typically less than 6.5 and 8 atom %, respectively, have been characterized as a function of the chemical nature of the catalyst, the synthesis temperature, and the hydrogen carrying diluent gas. These results are discussed with respect to the structural characterization performed by electron energy loss spectroscopy measurements, transmission electron microscopy and X-ray photoelectron spectroscopy.Journal of Physical Chemistry C. 01/2007; 111(28):10353-10358. -
Article: Angular and local spectroscopic analysis to probe the vertical alignment of N-doped well-separated carbon nanotubes.
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ABSTRACT: Vertically aligned well-separated N-doped multiwalled carbon nanotubes (CNTs) were grown on a silicon substrate by plasma enhanced chemical vapor deposition (PECVD). Angular near-edge X-ray absorption fine structure (NEXAFS) was used to investigate the vertical alignment of as-grown CNTs. In addition, both individual tubes and tube bundles were characterized by high-resolution electron energy loss spectroscopy (HREELS). Simultaneous analysis of both spectroscopic techniques provides information on chemical environment, orbital orientation between carbon and heteroatoms, and local curvature effects. We demonstrate the utility of NEXAFS as an in situ probe of CNTs.The Journal of Physical Chemistry B 09/2006; 110(32):15659-62. · 3.70 Impact Factor -
Article: Oriented carbon nanostructures containing nitrogen obtained by ion beam assisted deposition.
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ABSTRACT: In this paper, we report the deposition of graphite multilayer containing nitrogen covering nanometric nickel particles. In-situ photoelectron emission spectroscopy (XPS) reveals the presence of nitrogen in the carbon layer covering the nickel particles. The field emission properties of the structures are reported. Atomic force microscopy displays regular domelike structures. Raman spectroscopy shows the characteristic frequencies associated with graphite and disordered structures. High-resolution transmission electron microscopy confirms the presence of multiwall well-organized graphite layers covering the nickel particles. Disorder increases on increasing nitrogen content. The samples were prepared in-situ by depositing first a few atomic layers of nickel and subsequent islands formation by thermal annealing. Then, an argon ion beam bombards an ultrapure carbon target and simultaneously the growing film is assisted with a second low-energy nitrogen ion beam (ion beam assisted deposition).Journal of Nanoscience and Nanotechnology 03/2005; 5(2):188-91. · 1.56 Impact Factor -
Article: Room temperature synthesis of carbon nanofibers containing nitrogen by plasma-enhanced chemical vapor deposition
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ABSTRACT: This letter reports low-pressure, room-temperature growth of carbon nanofibers containing nitrogen by plasma chemical vapor deposition arrangement. By alternating pure acetylene plasma and afterglow pure nitrogen high dense plasma, a fine control of the fibers growth kinetic is obtained. This layer-by-layer deposition technique takes advantage of nitrogen chemical etching effects during the growth of nitrogen-doped carbon nanofibers.Applied Physics Letters 08/2004; 85(7):1244-1246. · 3.84 Impact Factor -
Article: Growth kinetics of low temperature single-wall and few walled carbon nanotubes grown by plasma enhanced chemical vapor deposition
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ABSTRACT: Single-wall, double walled or few walled nanotubes (FWNT) are grown by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) at temperature as low as 600 °C. Most of these structures are isolated and self-oriented perpendicular to the substrate. The growth mechanism observed for single-wall and few walled (less than seven walls) nanotubes is the “base-growth” mode. Their grow kinetics is investigated regarding two parameters namely the growth time and the synthesis temperature. It is shown that nucleation and growth rate is correlated with the number of walls into FWNT. It also provides an evidence of a critical temperature for FWNT synthesis.Physica E Low-dimensional Systems and Nanostructures 37:34-39. · 1.53 Impact Factor -
Article: Limits of the PECVD process for single wall carbon nanotubes growth
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ABSTRACT: This Letter explores the capabilities of plasma enhanced chemical vapor deposition to grow vertical oriented single wall, double wall or multi walled carbon nanotubes (CNTs). Our dual process uses high-density low-pressure plasma excited by electron cyclotron resonance using acetylene diluted in ammonia. The early stages of CNTs synthesis have been probed taking advantage of the low growth rate of our process. Two antagonist effects have been shown up: the formation of catalyzed carbon nanotubes against ion assisted bonds breaking. The limits of plasma single wall CNTs growth are discussed and transitory stages have been revealed for the first time.Chemical Physics Letters. -
Article: Single chamber PVD/PECVD process for in situ control of the catalyst activity on carbon nanotubes growth
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ABSTRACT: In this paper, we studied the effect of oxygen on the catalyst activity and related influence on the nanotubes (CNTs) growth by low-pressure/high-density plasma. CNTs were prepared using a novel single vacuum chamber reactor combining (i) plasma assisted physical vapour deposition (PVD) for catalyst deposition under O2, NH3 or Ar atmosphere with (ii) electron cyclotron resonance (ECR) C2H2/NH3 plasma enhanced chemical vapour deposition (PECVD) process for carbon nanotubes growth. The substrates are in situ prepared by controlled PVD allowing the deposition of sub-nanometric catalyst (Fe, Ni, Pd) films followed by ECR-PECVD CNTs growth. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis of CNTs show that the volume oxidation of the nanometric catalyst particles partially inhibits the CNTs growth while the catalyst surface oxidation can be reduced by the atomic nitrogen during the PECVD process. The specially designed PVD/PECVD process preserves the catalyst from moisture contamination, reducing walls nanotube defects.Surface and Coatings Technology. -
Article: Carbon nanotube growth mechanism switches from tip- to base-growth with decreasing catalyst particle size
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ABSTRACT: The growth of carbon nanotubes by a plasma assisted catalytic chemical vapor deposition was investigated using cobalt, nickel and iron catalyst particles of different sizes. For the three catalysts examined, it was shown that the growth mode switches from “tip-growth” for large particles (>>5 nm) to “base-growth” for smaller ones (<5 nm). While single-walled nanotubes and those with few walls (typically <7 walls) grow from their base, larger multi-walled nanotubes are fed with carbon via their tips which support the catalyst particle. A growth scenario involving two different pathways for carbon diffusion is proposed in order to explain the change in growth mode.Carbon.
Top co-authors
Top Journals
Institutions
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2007
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Institut des Materiaux Jean Rouxel
Strasbourg, Alsace, France
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2005
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Universidade Estadual de Campinas
- Instituto de Física "Gleb Wataghin" (IFGW)
Campinas, Estado de Sao Paulo, Brazil
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2004–2005
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French National Centre for Scientific Research
Lyon, Rhone-Alpes, France
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