Experimental determination of the first Townsend ionization coefficient in mixtures of Ar and N<sub>2</sub>

Talviste, Rasmus; Paris, P.; Raud, Jüri; Plank, Toomas; Erme, Kalev; Jõgi, Indrek

doi:10.1088/1361-6463/ac1d14

Cited by 5 publications

(2 citation statements)

References 62 publications

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“…The current density of a normal glow discharge is expressed as follows: where jng is the current density; 𝜀 is the dielectric constant; 𝛾 is the secondary electron emission coefficient; 𝐸 𝑝 ⁄ is the reduced electric field in the vicinity of the cathode surface; 𝛼 is the Townsend ionization coefficient; 𝑣 is the ion drift velocity, and 𝐸 𝑝 ⁄ is the reduced electric field [50]. The 𝛼 of argon is almost one-order higher than that of nitrogen, around 200 Td in a reduced electric field [51]. In other words, the higher applied voltage at nitrogen gas is more necessary than that at argon gas for the same Townsend coefficient value.…”

Section: Electrical Characteristics Of Glow Plasmamentioning

confidence: 99%

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Sato,

Igarashi,

Takahashi

et al. 2024

Processes

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High-density nitrogen plasma was produced using a high-power pulsed power modulator to sputter titanium targets for the preparation of titanium nitride film. The high-power pulsed sputtering discharge unit consisted of two targets facing each other with the same electrical potential. The titanium target plates were used as target materials with dimensions of 60 mm length, 20 mm height, and 5 mm thickness. The gap length was set to be 10 mm. The magnetic field was created with a permanent magnet array behind the targets. The magnetic field strength at the gap between the target plates was 70 mT. The electrons were trapped by the magnetic and electric fields to enhance the ionization in the gap. The nitrogen and argon gases were injected into the chamber with 4 Pa gas pressure. The applied voltage to the target plates had an amplitude from −600 V to −1000 V with 600 μs in pulse width. The target current was approximately 10 A with the consumed power of 13 kW. The discharge sustaining voltage was almost constant and independent of the applied voltage, in the same manner as the conventional normal glow discharge. The ion density and electron temperature at the surface of the ionization region were obtained as 1.7 × 1019 m−3 and 3.4 eV, respectively, by the double probe measurements. The vertical distribution of ion density and electron temperature ranged from 1.1 × 1017 m−3 (at 6 cm from the target edge) to 1.7 × 1019 m−3 and from 2.4 eV (at 6 cm from the target edge) to 3.4 eV, respectively. From the emission spectra, the intensities of titanium atoms (Ti I), titanium ions (Ti II), and nitrogen ions (N2+) increased with increasing input power. However, the intensities ratio of Ti II to Ti I was not affected by the intensities from N2+.

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Section: Electrical Characteristics Of Glow Plasmamentioning

confidence: 99%

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Sato,

Igarashi,

Takahashi

et al. 2024

Processes

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“…The density-reduced Townsend ionization coefficient α/N was determined in low-current electrical discharges under SST conditions many times in the past using the similar approach: usually the dependence of ln (I/I 0 ) on the electrode gap distance is measured for various E/N values, where I is the discharge current and I 0 is the initial current at the cathode. Examples include the recent measurements of α/N in gas mixtures of He with N 2 [109], Ar with N 2 [110] as well as the recent measurements of α eff /N in C5 perfluorinated ketone and its mixtures with air [111]. In the present modeling of an idealized SST setup, we have observed that the agreement between the two methods is very good, except for the lowest values of E/N, where the number of ionizing collisions is significantly reduced.…”

Section: Electron Swarm Transport Properties In An Idealized Sst Setupmentioning

confidence: 99%

Scanning drift tube measurements and kinetic studies of electron transport in CO

Dujko

Bošnjaković

Vass

et al. 2023

Plasma Sources Sci. Technol.

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We present scanning drift tube measurements of electron swarm transport coefficients in CO as a function of the reduced electric field E/N at room temperature under time-of-flight (TOF) conditions. The measurements are compared to modeling results and other available experimental data on swarm transport over the broad range of E/N from 2 Td to 1603 Td. The modeling results are obtained in Monte Carlo simulations and by solving the electron Boltzmann equation using a multi-term approach and the density gradient expansion procedure. We find generally good agreement between the measured and calculated transport coefficients. We propose a strategy to improve the cross-section set used to explain certain discrepancies at lower E/N values. Measurements and calculations of electron transport coefficients under hydrodynamic conditions are complemented by Monte Carlo simulations of electron transport in an idealized steady-state Townsend (SST) setup. The ionization coefficient is calculated as a function of E/N from the spatial density profiles of the electrons and compared to the corresponding values evaluated from the knowledge of the effective ionization frequency, drift velocity and longitudinal diffusion coefficient. Contrary to the traditional views, according to which the spatial relaxation of the mean energy and other transport properties for electrons in molecular gases is most commonly monotonic or quasi-monotonic, we find a `window' of E/N where the SST transport properties of the electrons exhibit oscillatory behavior as they relax towards the equilibrium state far downstream from the electron emitting boundary.

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Effective ionization coefficient in mixtures of Ar and O2 determined using the Townsend discharge

et al. 2022

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Precise knowledge of the fundamental ionization properties of gases, such as the effective ionization coefficient, is crucial for discharges in mixtures of Ar:O2, which are significant for a wide range of plasma applications. This study determined the effective ionization coefficient in electronegative gas mixtures of Ar:O2 in the pressure range of 10–800 Torr and reduced electric field strength E/ N range of 40–1200 Td utilizing a steady-state non-self-sustaining Townsend discharge. The reduced effective ionization coefficient α e/ N increased with E/ N and decreased with increasing O2 content in the gas mixture. The experimental results were compared with a model which was based on calculating the ionization and attachment coefficients with BOLSIG+. The ion conversion of O− to O2−, detachment from O2−, and formation of O3 were accounted for similarly as has been done with N2:O2 mixtures. Reasonably good agreement between the measurements and the model calculations was achieved for Ar:O2 mixtures with the O2 content between 20% and 70%. A discrepancy of more than 20% between measurement and calculations was observed at low E/ N values when the O2 content was below 20% and at high E/ N values when the O2 content was above 70%. Several possible explanations were proposed for the observed discrepancy; however, more elaborate models are required. The reduced critical electric field E/ N crit, where the apparent effective ionization coefficient is zero, was determined as a function of the O2 content in the Ar:O2 mixtures. E/ N crit increased with increasing O2 content in the mixture.

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Experimental determination of the first Townsend ionization coefficient in mixtures of Ar and N₂

Cited by 5 publications

References 62 publications

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Scanning drift tube measurements and kinetic studies of electron transport in CO

Effective ionization coefficient in mixtures of Ar and O2 determined using the Townsend discharge

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Experimental determination of the first Townsend ionization coefficient in mixtures of Ar and N2

Cited by 5 publications

References 62 publications

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

Scanning drift tube measurements and kinetic studies of electron transport in CO

Effective ionization coefficient in mixtures of Ar and O2 determined using the Townsend discharge

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Product

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Experimental determination of the first Townsend ionization coefficient in mixtures of Ar and N₂