Comparison of TALIF and catalytic probes for the determination of nitrogen atom density in a nitrogen plasma afterglow

Gaboriau, Freddy; Cvelbar, Uroš; Mozetič, Miran; Erradi, A; Rouffet, Benoît

doi:10.1088/0022-3727/42/5/055204

Cited by 34 publications

(26 citation statements)

References 33 publications

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“…Furthermore, the radical temperature is a priori not known since radicals are mainly produced by dissociation which is accompanied by a release of potential Franck-Condon energy 44 and T rad can, therefore, exceed the gas temperature considerably. β rad is a function of the radical species 49,83 , the surface material 50,81,83,84 , but most likely also a function of the surface condition 85 (for example, substrate temperature and roughness) and even the plasma parameters 81,86 (for example, ion flux). Values of β rad for one radical species and the same surface material can vary up to an order of magnitude in the literature (compare values in Refs.…”

Section: Wall Loss Times Of Radicals Determined From Afterglow Mementioning

confidence: 99%

Measurement and modeling of neutral, radical, and ion densities in H2-N2-Ar plasmas

Sode

Jacob

Schwarz-Selinger

et al. 2015

Journal of Applied Physics

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A comprehensive experimental investigation of absolute ion and neutral species densities in an inductively coupled H 2 -N 2 -Ar plasma was carried out. Additionally, the radical and ion densities were calculated using a zero-dimensional rate equation model. The H 2 -N 2 -Ar plasma was studied at a pressure of 1.5 Pa and an rf power of 200 W. The N 2 partial pressure fraction was varied between f N 2 = 0 % and 56 % by a simultaneous reduction of the H 2 partial pressure fraction. The Ar partial pressure fraction was held constant at about 1 %. NH 3 was found to be produced almost exclusively on the surfaces of the chamber wall. NH 3 contributes up to 12 % to the background gas.To calculate the radical densities with the rate equation model it is necessary to know the corresponding wall loss times t wrad of the radicals. t wrad was determined by the temporal decay of radical densities in the afterglow with ionization threshold mass spectrometry during pulsed operation and based on these experimental data the absolute densities of the radical species were calculated and compared to measurement results.Ion densities were determined using a plasma monitor (mass and energy resolved mass spectrometer). H + 3 is the dominant ion in the range of 0.0 ≤ f N 2 < 3.4 %. For 3.4 < f N 2 < 40 % NH + 3 and NH + 4 are the most abundant ions and agree with each other within the experimental uncertainty. For f N 2 = 56 % N 2 H + is the dominant ion while NH + 3 and NH + 4 have only a slightly lower density. Ion species with densities in the range between 0.5 and 10 % of n i,tot are H + 2 , ArH + , and NH + 2 . Ion species with densities less than 0.5 % of n i,tot are H + , Ar + , N + , and NH + . Our model describes the measured ion densities of the H 2 -N 2 -Ar plasma reasonably well. The ion chemistry, i.e., the production and loss processes of the ions and radicals, are discussed in detail. The main features, i.e., the qualitative abundance of the ion species and the ion density dependence on the N 2 partial pressure fraction, are well reproduced by the model.

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Section: Wall Loss Times Of Radicals Determined From Afterglow Mementioning

confidence: 99%

Measurement and modeling of neutral, radical, and ion densities in H2-N2-Ar plasmas

Sode

Jacob

Schwarz-Selinger

et al. 2015

Journal of Applied Physics

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“…One possibility could be a different surface temperature. Therefore, we consider the work of Gaboriau et al 10 .…”

Section: B Comparison With Literaturementioning

confidence: 99%

“…Gaboriau et al 10 determined β N of N on iron in a glass reactor at 40-400 Pa in the P of f phase. They determined β N with a fiber optic catalytic probe (see also Ref.…”

Section: B Comparison With Literaturementioning

confidence: 99%

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Wall loss of atomic nitrogen determined by ionization threshold mass spectrometry

Sode

Schwarz-Selinger

Jacob

et al. 2014

Journal of Applied Physics

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In the afterglow of an inductively coupled N 2 plasma relative N atom densities are measured by ionization threshold mass spectrometry (ITMS) as a function of time in order to determine the wall loss time t wN from the exponential decay curves. The procedure is performed with two mass spectrometers on different positions in the plasma chamber. t wN is determined for various pressures, i.e., for 3.0, 5.0, 7.5, and 10 Pa. For this conditions also the internal plasma parameters electron density n e and electron temperature T e are determined with the Langmuir probe and the rotational temperature T N 2 rot of N 2 is determined with the optical emission spectroscopy. For T N 2 rot a procedure is presented to evaluate the spectrum of the transition v' = 0 → v" = 2 of the second positive system (C 3 Π u → B 3 Π g ) of N 2 . With this method a gas temperature of 610 K is determined. For both mass spectrometers an increase of the wall loss times of atomic nitrogen with increasing pressure is observed. The wall loss time measured with the first mass spectrometer in the radial center of the cylindrical plasma vessel increases linearly from 0.31 ms for 3 Pa to 0.82 ms for 10 Pa. The wall loss time measured with the second mass spectrometer (further away from the discharge) is about 4 times higher. A model is applied to describe the measured t wN .The main loss mechanism of atomic nitrogen for the considered pressure is diffusion to the wall. The surface loss probability β N of atomic nitrogen on stainless steel was derived from t wN and is found to be 1 for the present conditions. The difference in wall loss times measured with the mass spectrometers on different positions in the plasma chamber is attributed to the different diffusion lengths.

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“…Collaboration of experts specialized in specific technique is encouraged. Some attempt has been already realized and they include comparison of TALIF and catalytic probes [69].…”

Section: Discussionmentioning

confidence: 99%

Extremely non-equilibrium oxygen plasma for direct synthesis of metal oxide nanowires on metallic substrates

Mozetič¹

2011

J. Phys. D: Appl. Phys.

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To cite this version:Miran Mozetic. Extremely non-equilibrium oxygen plasma for direct synthesis of metal oxide nanowires on metallic substrates. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (17), pp.174028. <10.1088/0022-3727/44/17/174028>. Extremely non-equilibrium oxygen plasma for direct synthesis of metal oxide nanowires on metallic substrates Miran Mozetic Department of Surface Engineering and Optoelectronics, Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, SloveniaA promising method for synthesis of metal oxide nanowires is based on application of extremely non-equilibrium gaseous environment found in oxygen plasma created by some types of discharges. The kinetic temperature of neutral gas is kept close to the room temperature, the electron temperature is few eV, the ionization fraction below 10 -6 and the dissociation fraction close to 100%. Plasma with such characteristics is obtained using electrode-less high frequency discharges driven by radiofrequency or microwave generators. Plasma parameters such as the electron density and energy distribution function, the Debye length, the dissociation and ionization fractions, the density of negatively charged molecules, the ratio between the positively charged molecules and atoms, the distribution of atoms and molecules over excited states, etc. depend on discharge parameters. The most important discharge parameters are the generator power, frequency and coupling, the purity and pressure of working gas and the gas flow, the dimensions of the discharge chamber, the materials facing plasma, the residual atmosphere, and, usually very important though often neglected, the properties of the samples mounted into a discharge chamber. Proper construction of the experimental system for synthesis of metal oxide nanowires allows for almost 100% dissociation fraction and thus extremely rapid growing of nanowires. The particularities of oxygen plasma as well as real -time monitoring of the dissociation fraction are elaborated in this contribution. The lack of reliable experimental results on characterization of extremely non-equilibrium oxygen plasma is stressed. Charged particles in cold weakly ionized plasmaGaseous plasma is partially ionized gas. Since there are always some charged particles presented in any gas, an additional requirement to this simple definition was stated: the gas is properly called plasma if the density of charged particles is large enough to screen any DC electrical potential at a length much smaller than the typical linear dimension of plasma. For the case of non-equilibrium low pressure plasma where the electrons in unperturbed plasma have much higher kinetic energy than positive ions, the requirement is often checked by comparison of the plasma dimension with the Debye length: ionized formation of a sheath separating unperturbed plasma and any object put into plasma.There is a potential drop through the sheath. In a rough approximation the potential drop is calculated using the following equation:Her...

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Comparison of TALIF and catalytic probes for the determination of nitrogen atom density in a nitrogen plasma afterglow

Cited by 34 publications

References 33 publications

Measurement and modeling of neutral, radical, and ion densities in H2-N2-Ar plasmas

Measurement and modeling of neutral, radical, and ion densities in H2-N2-Ar plasmas

Wall loss of atomic nitrogen determined by ionization threshold mass spectrometry

Extremely non-equilibrium oxygen plasma for direct synthesis of metal oxide nanowires on metallic substrates

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