Non-Neutral/Quasi-Neutral Plasma Edge Definition for Discharge Models: A Numerical Example for Dual Frequency Hydrogen Capacitively Coupled Plasmas

Salabas, A.; Brinkmann, Ralf Peter

doi:10.1143/jjap.45.5203

Cited by 20 publications

(19 citation statements)

References 39 publications

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“…The sheath extension is calculated as in Ref. 36, where the radial sheath edge S R is determined as the radius R that satisfies the Brinkmann criterion 37 .…”

Section: Experimental Methods and Simulation Modelmentioning

confidence: 99%

Inducing locally structured ion energy distributions in intermediate-pressure plasmas

et al. 2019

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Ion energy distribution functions (IEDFs) incident upon material surfaces in radio-frequency capacitively coupled plasmas (rf CCPs) are coupled to the spatial and temporal sheath dynamics.Tailoring the ion energy distribution function within intermediate-pressure plasmas (≈ 133 Pa, 1 Torr), finding application in surface modification and aerospace industries, is challenging due to the collisional conditions. In this work, experimentally benchmarked fluid/Monte-Carlo simulations are employed to demonstrate the production of structured IEDFs in a collisional (200 Pa 1.5 Torr argon) rf hollow cathode discharge. The formation of structures within the IEDFs is explained by an increase in the Ar + ion-neutral mean-free-path and simultaneous decrease in the phase-averaged sheath extension as the rf voltage frequency increases over 13.56 -108.48 MHz for a constant rf voltage amplitude (increasing plasma power) and gas flow rate. Two distinct transitions in the shape of the IEDF are observed at 450 V, corresponding to the formation of 'mid-energy' (60 -180 eV) structures between 40.68 -54.24 MHz and additional 'high energy' ( 180 eV) structures between 81.36 -94.92 MHz, the structures within each region displaying a distinct sensitivity to the applied 1 voltage amplitude. Transitions between these energy ranges occurred at lower applied voltages for increased applied voltage frequencies, providing increased control of the mean and modal ion energy over a wider voltage range. Capability to extend the range of access to an operational regime where the structured IEDFs are observed is desirable for applications that require control of the ion-bombardment energy under collisional plasma conditions.

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“…The sheath extension is calculated as in Ref. 36, where the radial sheath edge S R is determined as the radius R that satisfies the Brinkmann criterion 37 .…”

Section: Experimental Methods and Simulation Modelmentioning

confidence: 99%

Inducing locally structured ion energy distributions in intermediate-pressure plasmas

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The sheath extension is calculated as in Ref. 51, where the radial sheath edge S R is determined as the radius R that satisfies the Brinkmann criterion 62 .…”

Section: Description Of the Simulation Modelmentioning

confidence: 99%

Decoupling ion energy and flux in intermediate pressure capacitively coupled plasmas via tailored voltage waveforms

Doyle

Gibson

Boswell

et al. 2020

Plasma Sources Sci. Technol.

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The discrete control of ion energy and flux is of increasing importance to industrially relevent plasma sources. The ion energy distribution functions (IEDFs) and net ion flux incident upon material surfaces in intermediate pressure (≈ 133 Pa, 1 Torr) radio-frequency capacitively coupled plasmas (rf CCPs) are coupled to the spatio-temporal sheath dynamics and resulting phaseaveraged sheath potential. For single frequency driven discharges this co-dependence of ion energy and flux on the sheath potential limits the range of accessible operating regimes. In this work, experimentally benchmarked 2D fluid/Monte-Carlo simulations are employed to demonstrate quasiindependent control of the ion flux and IEDF incident upon plasma facing surfaces in a collisional (≈ 200 Pa, 1.5 Torr argon) rf hollow cathode discharge driven by multi-harmonic (n ≥ 2) tailored voltage waveforms. The application of variable phase offset n = 5 tailored voltage waveforms affords a significant degree of control over the ion flux Γ Ar + and mean ion energy ǫAr + , modulating each by 1 factors of 2.9 and 1.6, respectively as compared to 1.8 and 1.6, achieved via n = 2 dual-frequency voltage waveforms. The disparate modulations achieved employing n = 5 tailored voltage waveforms demonstrate a significant degree of independent control over the mean ion energy and ion flux for collisional conditions, enabling access to a wider range of operational regimes. Maximising the extent to which ion energy and flux may be independently controlled enables improvements to plasma sources for technological applications such as plasma assisted material manufacture and spacecraft propulsion.

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“…The solid line indicates the boundary between the plasma bulk and the plasma boundary sheaths, which is determined assuming an equivalent sharp electron step. 23 Under these conditions the plasma operates in the controlled ␣-mode, where the excitation mechanisms are volumetric. This mode is mainly driven by the electron current density, leading to pronounced excitation structures during sheath expansion and sheath collapse.…”

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confidence: 99%

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

2010

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Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

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Non-Neutral/Quasi-Neutral Plasma Edge Definition for Discharge Models: A Numerical Example for Dual Frequency Hydrogen Capacitively Coupled Plasmas

Cited by 20 publications

References 39 publications

Inducing locally structured ion energy distributions in intermediate-pressure plasmas

Inducing locally structured ion energy distributions in intermediate-pressure plasmas

Decoupling ion energy and flux in intermediate pressure capacitively coupled plasmas via tailored voltage waveforms

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

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