Heterogeneous and homogeneous hydrogen kinetics in plasma chemistry

Otorbaev, DK; Sanden, van de Mcm Richard; Schram, DC Daan

doi:10.1088/0963-0252/4/2/013

Cited by 19 publications

(10 citation statements)

References 59 publications

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“…The E-R mechanism can yield vibrationally excited molecules in the whole vibrational manifold for physisorbed atoms and up to v = 4 for chemisorbed atoms. The E-R mechanism has been also studied, by other authors, on copper and tungsten surfaces [55], [56] obtaining results similar to those described by Billing…”

Section: Wall Effectssupporting

confidence: 67%

Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

et al. 2006

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Old and new problems in the physics of multicusp magnetic sources for the production of negative H -/Dions are presented and discussed. We emphasize particularly, in this kind of plasmas, both the vibrational and electron non equilibrium energy distributions, the role of Rydberg states in enhancing the negative ion production, the production of vibrationally excited states by the Eley-Rideal mechanism, and the enhancement of negative ion concentrations in pulsed discharges. In appendix I recent cross sections calculations for elementary processes and the theoretical determination of hydrogen recombination probability on graphite surface are illustrated. In appendix II two types of sources are modeled: the first one is a classical negative ion source in which the plasma is generated by thermoemitted electrons; in the second one, electrons already present in the mixture are accelerated by an RF field to sufficiently high energy to ionize the gas molecules.

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Section: Wall Effectssupporting

confidence: 67%

Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

et al. 2006

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“…In accordance with that, a free atom is more likely to recombine with one adsorbed on a surface. This means that a hydrogenated surface exhibits a high recombination coefficient 154 . Therefore, we can point the recombination on the surface as well as in the bulk as potential pathways for net reduction in moles as observed in Figure 6.4.1.…”

Section: The Interaction Of Hydrogen With Metalsmentioning

confidence: 99%

Plasma catalysis using low melting point metals.

Carreon¹

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Plasma catalysis is emerging as one of the most promising alternatives to carry out several reactions of great environmental importance, from the synthesis of nanomaterials to chemicals of great interest. However, the combined effect of a catalyst and plasma is not clear. For the particular case of 1-D nanomaterials growth, the low temperatures synthesis is still a challenge to overcome for its scalable manufacturing on flexible substrates and thin metal foils. Herein, the use of low-melting-point metal clusters under plasma excitation was investigated to determine the effectiveness in their ability to catalyze the growth of 1-D nanomaterials. Specifically, plasma catalysis using Gallium (Ga) was studied for the growth of silicon nanowires. The synthesis experiments using silane in hydrogen flow over Ga droplets in the presence of plasma excitation yielded tip-led growth of silicon nanowires. In the absence of plasma, Ga droplets did not lead to silicon nanowire growth, indicating the plasma-catalyst synergistic effect when using Ga as catalyst. The resulting nanowires had a 1:1 droplet diameter to nanowire diameter relationship when the droplet diameters were less than 100 nm. From 100 nm to a micron, the ratio increased from 1:1 to 2:1 due to differences with wetting behavior as a function of droplet size. The growth vi experiments using Ga droplets derived from the reduction of Gallium oxide nanoparticles resulted in silicon nanowires with size distribution similar to that of Gallium oxide nanoparticles. Systematic experiments over 100 ºC-500 ºC range suggest that the lowest temperature for the synthesis of silicon nanowires using the plasma-gallium system is 200 ºC. A set of experiments using Ga alloys with aluminum and gold was also conducted. The results show that both Ga rich alloys (Ga-Al and Ga-Au) allowed the growth of silicon nanowires at a temperature as low as 200 ºC. This temperature is the lowest reported when using either pure Al or Au. The estimated activation energy barrier for silicon nanowire growth kinetics using AlGa alloy (~48.6 kJ/mol) was higher compared to that using either pure Ga or Ga-Au alloy (~34 kJ/mol). The interaction between Ga and hydrogen was measured experimentally by monitoring pressure changes in a Ga packed batch reactor at constant temperature. The decrease of the pressure inside the reactor when the Ga was exposed to plasma indicated the absorption of hydrogen in Ga. The opposite effect is observed when the plasma is turned off suggesting that hydrogen desorbed from Ga. This experimental observation suggests that Ga acts as hydrogen sink in the presence of plasma. The formation of Ga-H species in the Ga surface and in the bulk as intermediate is suggested to be responsible for the dehydrogenation of silyl radicals from the gas phase and subsequently for selective dissolution of silicon into molten Ga. The proposed reaction mechanism is also consistent with the experimentally determined activation barrier for growth kinetics (~34 kJ/mol). In addition, theoretical simulati...

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“…According to literature hydrogen is very easily adsorbed by the surfaces of the metal, mainly in atomic form. 29 Also, it has been observed that H atoms react by etching the deposit film restoring Si-H bonds in silane plasma. 31 Another explanation for this low energy component could be the dissociative excitation of NHx radicals by electron impact producing slow excited H atoms.…”

Section: Writing the Density Ratiomentioning

confidence: 99%

Hydrogen Balmer line broadening in Ar-N₂-SiH₄ DC glow discharge

Jauberteau

2022

Journal of Applied Physics

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Broadened hydrogen Balmer lines are observed in a DC glow discharge sustained in Ar–SiH4–N2 gas mixture. This broadening is due to the Doppler frequency shift. H atoms’ translational energy distribution is calculated in different positions between the two electrodes of the discharge along the interelectrode axis and in different gas mixtures. Three main components are observed at 0.6(±0.5) eV, 12(±3) eV, 62(±6) eV, 1(±1) eV, 28(±6) eV, and 105(±12) eV for Hα and Hβ, respectively. They correspond to hydrogen dissociation by electron impact producing H(n = 3, 4) atoms and dissociative recombination of the ion in the cathode fall or backscattered fast H atoms on the cathode surface. The density ratio nH2/nAr ranges from 44% to 13% or from 10% to 3% when a = nH/nH2 = 0.01 and 0.1, respectively, in function of the gas mixture. So, large hydrogen density could be due to hydrogen desorption from the wall and cathodes and/or to the gas recirculation within the reactor. A new low energy component is observed in the Hα line profile, when silane and nitrogen concentrations decrease and increase, respectively. It could also be due to the H atom desorbing from the reactor wall or NHx species dissociated by an electron impact within the reactor.

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Heterogeneous and homogeneous hydrogen kinetics in plasma chemistry

Cited by 19 publications

References 59 publications

Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

Plasma catalysis using low melting point metals.

Hydrogen Balmer line broadening in Ar-N₂-SiH₄ DC glow discharge

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Heterogeneous and homogeneous hydrogen kinetics in plasma chemistry

Cited by 19 publications

References 59 publications

Vibrational kinetics, electron dynamics and elementary processes in H2and D2plasmas for negative ion production: modelling aspects

Vibrational kinetics, electron dynamics and elementary processes in H2and D2plasmas for negative ion production: modelling aspects

Plasma catalysis using low melting point metals.

Hydrogen Balmer line broadening in Ar-N2-SiH4 DC glow discharge

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Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

Vibrational kinetics, electron dynamics and elementary processes in H₂and D₂plasmas for negative ion production: modelling aspects

Hydrogen Balmer line broadening in Ar-N₂-SiH₄ DC glow discharge