molecular ions in helium glow discharges: the effect of bulk electron temperature

Kutasi, Kinga; Hartmann, P.; Bánó, Gregor

doi:10.1088/0963-0252/14/2/s01

Cited by 19 publications

(17 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the electron density n e-, the values calculated are 1.8 9 10 11 and 5.6 9 10 11 cm -3 without and with filaments, respectively. These values correspond to a mole fraction of 3.3 9 10 -6 and 1.05 9 10 -5 , respectively, in good agreement with a theoretical estimation [30] and simulations performed in similar processes like microwave discharges [14,48,49] and DC discharges [50,51]. Even if it must be recalled that such comparisons may be handled with care because of different experimental conditions (gas, pressure, plasma power, experimental set up, ...), nevertheless the same order of magnitude is found.…”

Section: Effect Of the Gas Activation Modesupporting

confidence: 87%

An Investigation of the Plasma Composition in Plasma-enhanced Hot Filament Catalytic Chemical Vapor Deposition of Carbon Nanotubes

Gulas

Cojocaru

Normand

et al. 2007

Plasma Chem Plasma Process

View full text Add to dashboard Cite

A mixture of acetylene, hydrogen and ammonia (C 2 H 2 /H 2 /NH 3 ) is used to produce carbon nanotubes (CNTs) by a plasma-enhanced catalytic chemical vapor deposition process either without (PE CCVD) or with hot filaments-assistance (PE HF CCVD). A mathematical model based on Chemkin computer package is used for analyzing specific conditions of nanotube synthesis. Simulations are compared with optical emission spectroscopy (OES) measurements. Morphological and structural investigations on the grown carbon nanostructures are also performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that the significant change in the density and the morphology of the CNTs grown in the presence of NH 3 could be mainly explained by the gas phase formation of CN and HCN. Both species display a high etching activity, whereas the species C, CH, CH 2 , CH 2 (S), C 2 and C 2 H are expected to be the most probable carbon nanotube precursors.

show abstract

Section: Effect Of the Gas Activation Modesupporting

confidence: 87%

An Investigation of the Plasma Composition in Plasma-enhanced Hot Filament Catalytic Chemical Vapor Deposition of Carbon Nanotubes

Gulas

Cojocaru

Normand

et al. 2007

Plasma Chem Plasma Process

View full text Add to dashboard Cite

show abstract

“…The computations are carried out at the following values of the secondary electron emission coefficients: γ He + = 0.15, γ He + 2 = 0.1, γ N + 2 = 0.05, and γ ph = 0.1, where the last value refers to the VUV resonance photons radiated from the He 2 1 P state. These ion-induced yields of the helium ionic species are somewhat lower than those adopted in [31], for He + we base our choice on the findings of [38,39], and for He + 2 we apply the findings of [40] that their yield is ≈ 60% of the yield of atomic ions. These coefficients are known, of course, to have a large uncertainty related to the properties of the electrode surfaces (see, e.g., [41]).…”

Section: Resultsmentioning

confidence: 99%

The effect of photoemission on nanosecond helium microdischarges at atmospheric pressure

Hamaguchi

Gans

2018

Plasma Sources Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Atmospheric-pressure microdischarges excited by nanosecond highvoltage pulses are investigated in helium-nitrogen mixtures by first-principles particlebased simulations that include VUV resonance radiation transport via tracing photon trajectories. The VUV photons, of which the frequency redistribution in emission processes is included in some detail, are found to modify remarkably the computed discharge characteristics due to their ability to induce electron emission from the cathode surface. The electrons created this way enhance the plasma density and a significant increase of the transient current pulse amplitude is observed. The simulations allow the computation of the density of helium atoms in the 2 1 P resonant state, as well as the density of photons in the plasma and the line shape of the resonant VUV radiation reaching the electrodes. These indicate the presence of significant radiation trapping in the plasma and photon escape times longer than the duration of the excitation pulses are found.

show abstract

“…The mobility coefficient usually has an experimental value, and constant characteristic energy values between kT e = 0.1 and 1 eV have routinely been used [44][45][46][47] to obtain the diffusion coefficient D e , via the relation D e /µ e = ekT e . The effect of the assumed value of the (slow, or bulk) characteristic electron energy kT e has been analysed in [16,48]. It has been shown that some of the calculated discharge characteristics (particle densities and the depth of the potential well formed in the negative glow) depend sensitively on the assumed value of kT e , while some other characteristics (particle fluxes and the voltage-current characteristics of the discharge) are basically independent of this value.…”

Section: Transport Coefficientsmentioning

confidence: 99%

On the accuracy and limitations of fluid models of the cathode region of dc glow discharges

Derzsi

Hartmann

Korolov

et al. 2009

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

This paper compares the performance and limitations of different models of the cathode region of cold-cathode low-pressure dc glow discharges: (i) we review known modelling approaches, (ii) develop our own simulation codes based on these approaches, (iii) perform calculations using these codes for reference sets of discharge conditions, which allows a critical comparison of the models and (iv) for a further check of the simulation results we carry out Langmuir probe measurements of electron densities in abnormal Ar glow discharges. The theoretical approaches include fluid models both neglecting and including the electron energy balance equation, as well as hybrid models, which combine the fluid treatment of slow plasma species with the kinetic simulation of fast electrons. We also test the effect of the choice of the ionization source term in fluid models. We find that the electron densities calculated from the fluid models are far (several orders of magnitude) below the experimental values even if the electron energy equation is considered in the calculations. This weakness of fluid models clearly points out the importance of an accurate calculation of the ionization source term, which can only be accomplished by a kinetic approach under the conditions of highly nonlocal electron transport in the cathode region of glow discharges. In hybrid models Monte Carlo simulation is used for this purpose, and indeed, this approach gives electron densities comparable to our experimental data.

show abstract

molecular ions in helium glow discharges: the effect of bulk electron temperature

Cited by 19 publications

References 39 publications

An Investigation of the Plasma Composition in Plasma-enhanced Hot Filament Catalytic Chemical Vapor Deposition of Carbon Nanotubes

An Investigation of the Plasma Composition in Plasma-enhanced Hot Filament Catalytic Chemical Vapor Deposition of Carbon Nanotubes

The effect of photoemission on nanosecond helium microdischarges at atmospheric pressure

On the accuracy and limitations of fluid models of the cathode region of dc glow discharges

Contact Info

Product

Resources

About