Optical emission spectroscopy of reactive plasmas: A method for correlating emission intensities to reactive particle density

Coburn, J. W.; Chen, M.

doi:10.1063/1.328060

Cited by 879 publications

(402 citation statements)

References 7 publications

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“…For optical actinometry normally a rare gas of known concentration is added to the plasma to quantify the unknown concentration of a molecular or radical species 47 . The emitted light of two neighboring emission lines, one from the actinomer-the added nobel gas-and one from the species of interest are measured.…”

Section: Optical Actinometrymentioning

confidence: 99%

Quantitative determination of mass-resolved ion densities in H2-Ar inductively coupled radio frequency plasmas

Sode

Schwarz-Selinger

Jacob

2013

Journal of Applied Physics

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Inductively coupled H 2 -Ar plasmas are characterized by an energy-dispersive mass spectrometer (plasma monitor), a retarding field analyzer, optical emission spectroscopy and a Langmuir probe. A procedure is presented that allows determining quantitatively the absolute ion densities of Ar + , H + , H + 2 , H + 3 and ArH + from the plasma monitor raw signals. The calibration procedure considers the energy and mass-dependent transmission of the plasma monitor. It is shown that an additional diagnostic like a Langmuir probe or a retarding field analyzer is necessary to derive absolute fluxes with the plasma monitor. The conversion from fluxes into densities is based on a sheath and density profile model.Measurements were conducted for a total gas pressure of 1.0 Pa. For pure H 2 plasmas the dominant ion is H + 3 . For mixed H 2 -Ar plasmas the ArH + molecular ion is the most dominant ion species in a wide parameter range. The electron density n e is around 3 × 10 16 m −3 and the electron temperature T e decreases from 5 to 3 eV with increasing Ar content. The dissociation degree was measured by actinometry. It is around 1.7 % nearly independent on Ar content. The gas temperature, estimated by the rotational distribution of the Q-branch lines of the H 2 Fulcher-α diagonal band (v' = v" = 2) is estimated to (540±50) K.

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Section: Optical Actinometrymentioning

confidence: 99%

Quantitative determination of mass-resolved ion densities in H2-Ar inductively coupled radio frequency plasmas

Sode

Schwarz-Selinger

Jacob

2013

Journal of Applied Physics

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“…In this paper an examination of actinometry as a method for monitoring atomic oxygen ground state number density in an industrial RF capacitive etch plasmas is undertaken. Actinometry, which was first proposed by Coburn and Chen to monitor atomic fluorine density in RF capacitive systems [13] is based on measuring the ratio of two optical emission lines from the plasma; one from the species of interest and the other from trace amounts of a noble gas actinometer of known concentration (typically argon at < 5%) which is added to the system to allow implementation of the technique. The actinometer is deliberately introduced at low concentration to avoid disturbing the plasma.…”

Section: Introductionmentioning

confidence: 99%

Use of particle-in-cell simulations to improve the actinometry technique for determination of absolute atomic oxygen density

Conway

Kechkar

Connor

et al. 2013

Plasma Sources Sci. Technol.

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Actinometry is a non-invasive optical technique that can be used to quantitatively monitor atomic oxygen number densities [O] in gas discharges under certain operating conditions. However, careless application of the technique can lead to erroneous conclusions regarding the behaviour of atomic oxygen in plasma. One limitation on this technique is an accurate knowledge of the various rate constants required, which in turn is hampered by an insufficiently precise knowledge of the Electron Energy Distribution Function (EEDF) in the plasma. In this work Particle in Cell (PIC) simulations have been used to generate theoretical EEDFs. To validate a simulation the electron density n e produced by the PIC code is compared to experimental n e values measured using a hairpin probe. The PIC input parameters are adjusted to optimise agreement between the PIC and experimental n e results. This approach should in principle yield an EEDF that more accurately reflects the true EEDF in the plasma. The PIC EEDF is then used to generate rate constants for the actinometry model which should improve the accuracy of the quantitative [O] result for that particular set of plasma conditions. The actinometry [O] results are then compared to [O] results obtained using Two-photon Absorption Laser Induced Fluorescence (TALIF) to validate the approach.

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“…This classical actinometry concept implies that the excited states, are not populated via cascades from higher levels, by excitation from lower metastable states, via dissociation, by collisional transfer, and reabsorption of radiation, and are not depopulated by collisional quenching. 8 Under the assumption that the electron-impact excitation cross sections have the same shape and threshold, the ratio of the excitation rates is independent of the plasma conditions. This approach can provide a qualitative measurement of the atomic oxygen ground state density in low pressure plasmas with not too low degree of dissociation.…”

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confidence: 99%

Diagnostic based modeling for determining absolute atomic oxygen densities in atmospheric pressure helium-oxygen plasmas

Niemi

Reuter

Graham

et al. 2009

Applied Physics Letters

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Absolute atomic oxygen ground state densities in a radio-frequency driven atmospheric pressure plasma jet, operated in a helium-oxygen mixture, are determined using diagnostic based modeling. One-dimensional numerical simulations of the electron dynamics are combined with time integrated optical emission spectroscopy. The population dynamics of the upper O 3p P3 (λ=844 nm) atomic oxygen state is governed by direct electron impact excitation, dissociative excitation, radiation losses, and collisional induced quenching. Absolute values for atomic oxygen densities are obtained through comparison with the upper Ar 2p1 (λ=750.4 nm) state. Results for spatial profiles and power variations are presented and show excellent quantitative agreement with independent two-photon laser-induced fluorescence measurements.

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Optical emission spectroscopy of reactive plasmas: A method for correlating emission intensities to reactive particle density

Cited by 879 publications

References 7 publications

Quantitative determination of mass-resolved ion densities in H2-Ar inductively coupled radio frequency plasmas

Quantitative determination of mass-resolved ion densities in H2-Ar inductively coupled radio frequency plasmas

Use of particle-in-cell simulations to improve the actinometry technique for determination of absolute atomic oxygen density

Diagnostic based modeling for determining absolute atomic oxygen densities in atmospheric pressure helium-oxygen plasmas

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