Double-discharge plasma system for deposition of carbon nanostructures

Abstract

Deposition of carbon nanostructures from ethanol precursor at atmospheric pressure can be enhanced via the use of a double-discharge system - a microwave and a DC discharge. We used a surface-wave discharge at a frequency of 2.45 GHz in a gas mixture of Ar, H2 and C2H5OH to create a plasma column in a small-diameter ceramic tube and a plasma plume above it. The plume spectra in the UV/Vis range were measured by an optical system with an iHR550 spectrometer; the gas temperature and the electron temperature and density were calculated from the emission lines. The high gas temperature T g ∼3000 K and electron density (∼6×1020 m3) in the microwave plasma plume cause an effective dissociation of the ethanol even at low levels of absorbed power (10 W) and a strong carbon Swan band is registered in the spectrum. Transporting the created neutral and charged particles to the substrate at atmospheric pressure is difficult due to their short mean-free-path; we, therefore, applied an additional DC discharge. This two-discharge system allows more reactive species and ions from the ethanol decomposition to reach the substrate, thus speeding up the deposition of carbon nanostructures. Such structures were deposited on Ni foil and Ni foam substrates under fixed plasma parameters and controlled substrate temperature. The morphology of the produced graphene structures was studied using SEM and Raman spectroscopy.

Deposition of vertical carbon nanostructures by microwave plasma source on nickel and alumina

“…The Line Ratio Method is applied for simultaneous determination of plasma parameters from Ar spectral lines recorded at gas pressure ‫‬ = 0.6 ÷ 4 Torr (figure 2). The gas temperature ܶ is estimated to be in the range of 600 ÷ 700 K by optical emission spectroscopy methods, similar to our previous work on PECVD at atmospheric pressure [5]. The spectral lines selected for application of this method are: 696.5 nm ‫2(‬ ଶ → ‫ݏ1‬ ହ ), 706.72 nm ‫2(‬ ଷ → ‫ݏ1‬ ହ ) and 727.22 nm ‫2(‬ ଶ → ‫ݏ1‬ ସ ).…”

Model of slot antenna for MPECVD of carbon nanostructure

“…The gas mixture and the resulting plasma parameters at constant input power also affect the performance of the applicator because the plasma [3] is a variable load impedance that depends on the absorbed power. In the gas mixture (Ar/H 2 /CH 4 ) used in MPECVD process of carbon nanostructures [7] argon is the main gas sustaining the plasma column. Design of the microwave applicator for specific dimensions of the plasma reactor and applications requires that all the features of the vacuum chamber and the expected value of the plasma impedance [8] be taken into account to obtain it's optimal parameters.…”

Deposition of carbon nanolayers by PECVD on ceramic substrates

“…Our investigations on the deposition of carbon nanostructures on silicon carbide substrates by PECVD in a planar microwave discharge in a gas mixture of H 2 and CH 4 , brings up-to-date information for the development of new method and model for the deposition of graphene on ceramic materials. Previous studies on the deposition of thin carbon and graphene layers on metal substrates at atmospheric pressure have demonstrated the effectiveness of microwave discharges for PECVD [8].…”