On the formation and annihilation of the singlet molecular metastables in an oxygen discharge

Toneli, David; Pessoa, Rodrigo Sávio; Roberto, Marisa; Guðmundsson, Jón Tómas

doi:10.1088/0022-3727/48/32/325202

Cited by 44 publications

(60 citation statements)

References 74 publications

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“…Aluminum electrodes would therefore lead to higher singlet metastable densities and lower electronegativity. We have seen in global model studies that wall quenching can be the main loss mechanism for the singlet metastable state O 2 (b 1 Σ + g ) [3]. In these studies we assumed the quenching coefficient to be 0.1, which is the same value as that assumed in this current study.…”

Section: Resultsmentioning

confidence: 85%

“…The O + 2 -ions are in majority among the positive ions and the O + -ion density is much smaller and has a sharp decrease for pressures above 4 mTorr. It is also seen that the negative ion density ratio [O − ]/[O − 2 ] is 5.3 at 1 mTorr, and 1.3 at 100 mTorr [3]. Such global models studies neglect spatial variations in the plasma parameters as well as the kinetics of the discharge.…”

Section: Introductionmentioning

confidence: 99%

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On the role of metastable states in low pressure oxygen discharges

Guðmundsson

Hannesdottir

2017

AIP Conference Proceedings

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Abstract.We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the spatiotemporal evolution of the electron heating mechanism in a capacitively coupled oxygen discharge in the pressure range 10 -200 mTorr. The electron heating is most significant in the sheath vicinity during the sheath expansion phase. We explore how including and excluding detachment by the singlet metastable states O 2 (a 1 ∆ g ) and O 2 (b 1 Σ + g ) influences the heating mechanism, the effective electron temperature and electronegativity, in the oxygen discharge. We demonstrate that the detachment processes have a significant influence on the discharge properties, in particular for the higher pressures. At 10 mTorr the time averaged electron heating shows mainly ohmic heating in the plasma bulk (the electronegative core) and at higher pressures there is no ohmic heating in the plasma bulk, that is electron heating in the sheath regions dominates.

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Section: Resultsmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

On the role of metastable states in low pressure oxygen discharges

Guðmundsson

Hannesdottir

2017

AIP Conference Proceedings

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“…Further, the negative ions can strongly change the plasma dynamics as well as the plasma boundary sheath [51]. In particular, the collisional detachment of the negative ions with metastable oxygen molecules is an essential electron sources [52]. In consequence of the oxygen addition more energy loss channels occur by additional inelastic collisions resulting in dissociation, vibrational and rotational excitation, negative ion formation as well as heating of low energy electrons [53].…”

Section: Mode Transition and Plasma Parametersmentioning

confidence: 99%

E‐H Transition in Argon/Oxygen Inductively Coupled RF Plasmas

Wegner

Küllig

Meichsner

2015

Contrib. Plasma Phys.

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This contribution presents results of comprehensive investigation of the E-H transition in an inductively coupled radio frequency argon/oxygen discharge at 13.56 MHz. For the characterization of the discharge arrangement, the spatial magnetic and electric field components of the planar coil in vacuum are calculated and provide information about the electron heating region. The used double coil leads to a radial symmetric field distribution. Further, voltage and current probe measurements reveal the inductivity of the coil and the phase shift between the coil voltage and the current. As a result, the coil current and the RF voltage are directly proportional. The phase shift is nearly constant in the E-mode and decreases slightly in the H-mode. The positive ion saturation current as well as the line integrated electron density are measured by means of Langmuir probe and 160 GHz microwave interferometer, respectively, to study the mode transition in argon with different oxygen contents. The positive ion saturation current and the electron density decrease with increasing oxygen admixture at fixed pressure and RF power. The onset and the way of the E-H transition strongly depend on the oxygen content. The mode transition of a pure argon discharge is step like and changes to a continuous mode transition with the admixture of oxygen.

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“…The derivations are heuristically generalized for the electronegative plasmas in the asymptotic limits of the degree of electronegativity [20][21][22] and added with an ansatz [23]. The ansatz is later modified for a better accuracy [24] and one region parabolic profile is often neglected [16,17,25,26], since the flattening of the core becomes more important with the pressure [23]. Axial edge-to-centre ratios are recently benchmarked against spatially-resolved models in argon [27], and proposed in a new form for electropositive [28] and electronegative discharges [29].…”

Section: Introductionmentioning

confidence: 99%

“…Beside the ion losses, neutral wall flux for reflective wall might play a very important role on the plasma [16,30]. The neutral wall flux is either estimated for various geometries [31] or calculated by a simpler derivation [23,26,32]. Although, some ratios can be partially adaptable for the surface-wave discharges, they are not directly applicable in the considered pressure regime due to: (1) the structural electronegativity difference [33][34][35][36][37], (2) the detachment dominated negative ion loss mechanism of oxygen [38], (3) the unique axial characteristics of the surface-wave discharges and (4) the coaxial geometry.…”

Section: Introductionmentioning

confidence: 99%

A global model of cylindrical and coaxial surface-wave discharges

Kemaneci

Mitschker

Rudolph

et al. 2017

J. Phys. D: Appl. Phys.

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A volume-averaged global model is developed to investigate surface-wave discharges inside either cylindrical or coaxial structures. The neutral and ion wall flux is self-consistently estimated based on a simplified analytical description both for electropositive and electronegative plasmas. The simulation results are compared with experimental data from various discharge setups of either argon or oxygen, measured or obtained from literature, for a continuous and a pulse-modulated power input. A good agreement is observed between the simulations and the measurements. The calculations show that the wall flux often substantially contributes to the net loss rates of the individual species.

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On the formation and annihilation of the singlet molecular metastables in an oxygen discharge

Cited by 44 publications

References 74 publications

On the role of metastable states in low pressure oxygen discharges

On the role of metastable states in low pressure oxygen discharges

E‐H Transition in Argon/Oxygen Inductively Coupled RF Plasmas

A global model of cylindrical and coaxial surface-wave discharges

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