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1 Jun 2005

Volume 97, Issue 11, Articles (11xxxx)

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Experimental investigation of hybrid-evaporation-glow discharge plasma immersion ion implantation

L. H. Li, Y. Q. Wu, Y. H. Zhang, Ricky K. Y. Fu, and Paul K. Chu

J. Appl. Phys. 97, 113301 (2005); http://dx.doi.org/10.1063/1.1924880 (5 pages) | Cited 13 times

Online Publication Date: 25 May 2005

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High-voltage pulsed glow discharge is applied to plasma immersion ion implantation (PIII). In the glow discharge, the target constitutes the cathode and the gas tube forms the anode under a relatively high working gas pressure of 0.15–0.2 Pa. The characteristics of the glow discharge and ion density are measured experimentally. Our results show resemblance to hollow-anode glow discharge and the anode fall is faster than that of general glow discharge. Because of electron focusing in the anode tube orifice, ions are ionized efficiently and most of them impact the negatively biased samples. The resulting ion current density is higher than that in other PIII modes and possible mechanisms of the glow discharge PIII are proposed and discussed.
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52.80.Hc Glow; corona
52.50.Dg Plasma sources
52.77.Dq Plasma-based ion implantation and deposition
52.25.Fi Transport properties
52.70.-m Plasma diagnostic techniques and instrumentation
52.20.-j Elementary processes in plasmas

Impact of reductive N2/H2 plasma on porous low-dielectric constant SiCOH thin films

Hao Cui, Richard J. Carter, Darren L. Moore, Hua-Gen Peng, David W. Gidley, and Peter A. Burke

J. Appl. Phys. 97, 113302 (2005); http://dx.doi.org/10.1063/1.1926392 (8 pages) | Cited 19 times

Online Publication Date: 25 May 2005

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Porous low-dielectric constant (low-κ) SiCOH thin films deposited using a plasma-enhanced chemical-vapor deposition have been comprehensively characterized before and after exposure to a reactive-ion-etch-type plasma of N2 and H2 chemistry. The low-κ film studied in this work is a carbon-doped silicon oxide film with a dielectric constant (κ) of 2.5. Studies show that a top dense layer is formed as a result of significant surface film densification after exposure to N2/H2 plasma while the underlying bulk layer remains largely unchanged. The top dense layer is found to seal the porous bulk SiCOH film. SiCOH films experienced significant thickness reduction, κ increase, and leakage current degradation after plasma exposure, accompanied by density increase, pore collapse, carbon depletion, and moisture content increase in the top dense layer. Both film densification and removal processes during N2/H2 plasma treatment were found to play important roles in the thickness reduction and κ increase of this porous low-κ SiCOH film. A model based upon mutually limiting film densification and removal processes is proposed for the continuous thickness reduction during plasma exposure. A combination of surface film densification, thickness ratio increase of top dense layer to bulk layer, and moisture content increase results in the increase in κ value of this SiCOH film.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.05.Rm Porous materials; granular materials
77.22.Ch Permittivity (dielectric function)
52.77.Dq Plasma-based ion implantation and deposition
61.43.Gt Powders, porous materials
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Influence of dielectric barrier discharges on low Mach number shock waves at low to medium pressures

P. Bletzinger, B. N. Ganguly, and A. Garscadden

J. Appl. Phys. 97, 113303 (2005); http://dx.doi.org/10.1063/1.1922088 (6 pages) | Cited 3 times

Online Publication Date: 27 May 2005

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For shock wave propagation in nonequilibrium plasmas, it has been shown that when the electron Debye length exceeds the shock wave discontinuity dimension, strong double layers are generated, propagating with the shock wave. Strong double layer formation leads to the enhancement of the local excitation, ionization, and local neutral gas heating which increases the shock wave velocity. It is shown that dielectric barrier discharges (DBD) in pure N2 also increase the shock wave velocity and broaden the shock wave. The DBD is considerably more energy efficient in producing these effects compared to a dc glow discharge and can operate over a wide pressure range. It is shown that these effects are also operative in the pure N2 discharge afterglow, allowing a wide range of pulse repetition frequencies.
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52.35.Tc Shock waves and discontinuities
52.80.Hc Glow; corona
52.40.Kh Plasma sheaths
52.25.-b Plasma properties

Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

J. Qian, R. P. Joshi, J. Kolb, K. H. Schoenbach, J. Dickens, A. Neuber, M. Butcher, M. Cevallos, H. Krompholz, E. Schamiloglu, and J. Gaudet

J. Appl. Phys. 97, 113304 (2005); http://dx.doi.org/10.1063/1.1921338 (10 pages) | Cited 25 times

Online Publication Date: 31 May 2005

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An electrical breakdown model for liquids in response to a submicrosecond ( ∼ 100 ns) voltage pulse is presented, and quantitative evaluations carried out. It is proposed that breakdown is initiated by field emission at the interface of pre-existing microbubbles. Impact ionization within the microbubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. Continuous field emission at the streamer tip contributes to filament growth and propagation. This model can adequately explain almost all of the experimentally observed features, including dendritic structures and fluctuations in the prebreakdown current. Two-dimensional, time-dependent simulations have been carried out based on a continuum model for water, though the results are quite general. Monte Carlo simulations provide the relevant transport parameters for our model. Our quantitative predictions match the available data quite well, including the breakdown delay times and observed optical emission.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.22.Jp Dielectric breakdown and space-charge effects
79.70.+q Field emission, ionization, evaporation, and desorption
72.20.Ht High-field and nonlinear effects

Role of dissociative recombination in the excitation kinetics of an argon microwave plasma at atmospheric pressure

A. Sáinz, J. Margot, M. C. García, and M. D. Calzada

J. Appl. Phys. 97, 113305 (2005); http://dx.doi.org/10.1063/1.1922086 (11 pages) | Cited 16 times

Online Publication Date: 31 May 2005

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A collisional radiative model was developed in order to investigate the influence of dissociative recombination on the Saha–Boltzmann plasma equilibrium. As the dissociative recombination products are not well known, their relative importance was tested through comparison with the distribution of line intensities obtained in a microwave argon discharge produced at atmospheric pressure by a surface wave. It was found that the main dissociation products are the ground state and the 4s levels, the 5p and upper levels playing a negligible role. Because the higher levels are only weakly affected by dissociative recombination, they remain in partial local thermodynamic equilibrium. Therefore, the excitation temperature determined from these levels adequately describes the electron temperature. The model well reproduces experimental measurements of excitation temperature, rotational temperature, electron density, and absolute populations of the excited levels.
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52.20.Fs Electron collisions
52.80.Pi High-frequency and RF discharges
52.25.Kn Thermodynamics of plasmas

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar/H2 arc jet discharge

C. J. Rennick, R. Engeln, J. A. Smith, A. J. Orr-Ewing, M. N. R. Ashfold, and Yu. A. Mankelevich

J. Appl. Phys. 97, 113306 (2005); http://dx.doi.org/10.1063/1.1906288 (15 pages) | Cited 10 times

Online Publication Date: 1 June 2005

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A combination of experiment [optical emission and cavity ring-down spectroscopy (CRDS) of electronically excited H atoms] and two-dimensional (2D) modeling has enabled a uniquely detailed characterization of the key properties of the Ar/H2 plasma within a ⩽ 10-kW, twin-nozzle dc arc jet reactor. The modeling provides a detailed description of the initial conditions in the primary torch head and of the subsequent expansion of the plasma into the lower pressure reactor chamber, where it forms a cylindrical plume of activated gas comprising mainly of Ar, Ar+, H, ArH+, and free electrons. Subsequent reactions lead to the formation of H2 and electronically excited atoms, including H(n = 2) and H(n = 3) that radiate photons, giving the plume its characteristic intense emission. The modeling successfully reproduces the measured spatial distributions of H(n>1) atoms, and their variation with H2 flow rate, FH20. Computed H(n = 2) number densities show near-quantitative agreement with CRDS measurements of H(n = 2) absorption via the Balmer-β transition, successfully capturing the observed decrease in H(n = 2) density with increased FH20. Stark broadening of the Balmer-β transition depends upon the local electron density in close proximity to the H(n = 2) atoms. The modeling reveals that, at low FH20, the maxima in the electron and H(n = 2) atom distributions occur in different spatial regions of the plume; direct analysis of the Stark broadening of the Balmer-β line would thus lead to an underestimate of the peak electron density. The present study highlights the necessity of careful intercomparisons between quantitative experimental data and model predictions in the development of a numerical treatment of the arc jet plasma. The kinetic scheme used here succeeds in describing many disparate observations—e.g., electron and H(n = 2) number densities, spatial distributions of optical emission from the plume, the variation of these quantities with added flow of H2 and, when CH4 is added, absolute number densities and temperatures of radicals such as C2 and CH. The remaining limitations of the model are discussed.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.75.Hn Plasma torches
52.25.Dg Plasma kinetic equations
52.30.-q Plasma dynamics and flow
52.25.Tx Emission, absorption, and scattering of particles
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

Parameters of the plasma produced at the surface of a ferroelectric cathode by different driving pulses

O. Peleg, K. Chirko, V. Gurovich, J. Felsteiner, Ya. E. Krasik, and V. Bernshtam

J. Appl. Phys. 97, 113307 (2005); http://dx.doi.org/10.1063/1.1927704 (13 pages) | Cited 11 times

Online Publication Date: 7 June 2005

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Spectroscopic investigations of the properties of a plasma produced by a ferroelectric-plasma source are presented. The electron plasma density, the electron and ion temperature, and the density of desorbed neutrals near the ferroelectric surface are determined from spectral line intensities and profiles. Three different methods of surface plasma formation are analyzed using a simplified model for the plasma production. The model predicts the total amount of charge in the plasma to be proportional to the dielectric constant of the ferroelectric material. Also, the model shows a strong dependence of the plasma parameters on the resistivity of the plasma transition layer. A maximal plasma density of ∼ 1015 cm−3 is achieved when the electrons that were attached by the driving field to the ferroelectric surface are released from the surface owing to driving pulse sharp decay and ionized heavy atoms desorbed from the ferroelectric.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Dg Plasma sources
52.25.Ya Neutrals in plasmas
52.25.Mq Dielectric properties
52.25.Fi Transport properties
52.80.-s Electric discharges
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