Experimental and theoretical study of the effect of gas flow on gas temperature in an atmospheric pressure microplasma

Wang, Qiang; Doll, Florian; Donnelly, Vincent M.; Economou, Demetre J.; Sadeghi, N.; Franz, Gerhard

doi:10.1088/0022-3727/40/14/015

Cited by 89 publications

(88 citation statements)

References 33 publications

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“…The carbon in the CH radical derives from outgassing of the microwave substrate; 500 ppm hydrogen is added to the argon. The radiative lifetime of the CH A-state is on the order of 400 ns, 16 roughly of the same order as both electron-collisional quenching rate 17 for electron densities on the order of a few times 10 20 m À3 (see Sec. II C) and the collisional quenching rate by neutral argon.…”

Section: B Electrical and Spectroscopic Diagnosticsmentioning

confidence: 87%

Electron confinement and heating in microwave-sustained argon microplasmas

Hoskinson

Gregório

Parsons

et al. 2015

Journal of Applied Physics

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We systematically measure and model the behavior of argon microplasmas sustained by a broad range of microwave frequencies. The plasma behavior exhibits two distinct regimes. Up to a transition frequency of approximately 4 GHz, the electron density, directly measured by Stark broadening, increases rapidly with rising frequency. Above the transition frequency, the density remains approximately constant near 5 × 1020 m–3. The electrode voltage falls with rising frequency across both regimes, reaching approximately 5 V at the highest tested frequency. A fluid model of the plasma indicates that the falling electrode voltage reduces the electron temperature and significantly improves particle confinement, which in turn increases the plasma density. Particles are primarily lost to the electrodes at lower frequencies, but dissociative recombination becomes dominant as particle confinement improves. Recombination events produce excited argon atoms which are efficiently re-ionized, resulting in relatively constant ionization rates despite the falling electron temperature. The fast rates of recombination are the result of high densities of electrons and molecular ions in argon microplasmas.

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Section: B Electrical and Spectroscopic Diagnosticsmentioning

confidence: 87%

Electron confinement and heating in microwave-sustained argon microplasmas

Hoskinson

Gregório

Parsons

et al. 2015

Journal of Applied Physics

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“…For the experimental conditions of Fig. 5, the neutral atoms temperature of the magnetron plasma T a , which corresponds to the L r T value deduced from the two temperature fitting 25,26 , is 320 K; the 6 rotational distribution in the high J levels being represented by H r T =1500 K. For gas pressures of 0.6, 4.5 and 14 µbar, the T a deduced from the recorded nitrogen spectra at different discharge powers are plotted in figure 6 and range between 300 and 380 K. Values at intermediate pressures can be deduced by the interpolation of these data. As expected, at fixed pressure, T a increases with the dissipated power, but also slightly with the gas pressure 21 .…”

Section: -Gas Temperaturementioning

confidence: 94%

Section: -Gas Temperaturementioning

confidence: 99%

“…However, in argon plasmas, especially at low electron density conditions, the N 2 C; v'=0 level is also populated by the energy transfer reaction from the most abundant Ar*( 3 P 2 ) metastable atoms, which preferentially populates the high rotational levels (up to J = 55) of the C; v'=0 level, resulting in an 'effective rotational temperature' of about 2300 K 23,24 . Extended discussion on Botzmlann equilibrium in rotational levels by collisional transfers evidenced that in argon plasmas the equilibrium is barely reached and the high rotational levels of the C; v'=0 state always remain overpopulated 25 . To overcome this problem, the 0-0 band can be fitted assuming a two temperature rotational distribution according to the relation 25,26 : To measure the gas temperature, 10% nitrogen is added to the argon feed gas and the N 2 (C 3 Π u -B 3 Π g ) 0-0 band at 337 nm is recorded with the optical detection system described in section 2, by scanning the wavelength of the monochromator.…”

Section: -Gas Temperaturementioning

confidence: 99%

“…Extended discussion on Botzmlann equilibrium in rotational levels by collisional transfers evidenced that in argon plasmas the equilibrium is barely reached and the high rotational levels of the C; v'=0 state always remain overpopulated 25 . To overcome this problem, the 0-0 band can be fitted assuming a two temperature rotational distribution according to the relation 25,26 : T would correspond to distributions originating from electron impact excitation out of the ground state and to the energy transfer reaction from Ar* metastables, respectively.To measure the gas temperature, 10% nitrogen is added to the argon feed gas and the N 2 (C 3 Π u -B 3 Π g ) 0-0 band at 337 nm is recorded with the optical detection system described in section 2, by scanning the wavelength of the monochromator. The emission intensity of several argon and copper lines is monitored to ascertain that the introduction of 10% N 2 into argon do not introduce significant perturbation on magnetron discharge.…”

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confidence: 99%

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Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

Naghshara¹,

Sobhanian²,

Khorram³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract:In a dc-magnetron discharge with argon feed gas, densities of copper atoms in the ground state Cu( 2 S 1/2 ) and metastable state Cu*( 2 D 5/2 ) were measured by resonance absorption technique, using a commercial hollow cathode lamp as light source. The operating conditions were 0.3 -14 µbar argon pressure and 10 -200 W magnetron discharge power. The deposition rate of copper in a substrate positioned at 18 cm from the target was also measured with a quartz microbalance. The gas temperature, in the range of 300 to 380 K, was deduced from the emission spectral profile of N 2 (C 3 Π u − B 3 Π g ) 0-0 band at 337 nm when trace of nitrogen was added to the argon feed gas. The isotope-shifts and hyperfine structures of electronic states of Cu have been taken into account to deduce the emission and absorption line profiles, and hence for the determination of atoms densities from the measured absorption rates. To prevent error in evaluation of Cu density, attributed to the line profile distortion by autoabsorption inside the lamp, the lamp current was limited to 5 mA. Density of Cu( 2 S 1/2 ) atoms and deposition rate both increased with the enhanced magnetron discharge power but at fixed power the copper density augmented with argon pressure whereas the deposition rate followed the opposite trend. Whatever the gas pressure, the density of Cu*( 2 D 5/2 ) metastable atoms remained below the detection limit of 1 x 10 10 cm -3 for magnetron discharge powers below 50 W and hence increased much rapidly than the density of Cu( 2 S 1/2 ) atoms, over passing this later at some discharge power, whose value decreases with increasing argon pressure. This behavior is believed to result from the enhancement of plasma density with increasing discharge power and argon pressure, which would increase the excitation rate of copper into metastable states. At fixed pressure, the deposition rate followed the same trend than the total density of copper atoms in the ground and metastable states. Two important conclusions of this work are: i) copper atoms sputtered from the target under ion bombardment are almost all in the ground state Cu( 2 S 1/2 ) and hence in the plasma volume they can be excited into the metastable states; ii) all atoms in the long-lived ground and metastable states contributes to the deposition of copper layer on the substrate.a Corresponding author ; E-mail : nader.sadeghi@ujf-grenoble.fr 2 1-IntroductionMagnetron discharges are widely used for thin film deposition in surface treatment 1, 2 , magnetic and superconducting devices 3 , semiconductor industry 4 and in surface coating engineering of materials under low temperature conditions 5,6 . In these systems, the magnetic field, usually produced by placing permanent magnets behind the cathode, confines the plasma in the near cathode region, reducing the electron loss to the sidewalls. By increasing the ionization rate near the cathode, which is also the target to be sputtered, its confinement helps to maintain the plasma at much lower buffer gas pressure than...

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The analysis of nitrogen rotational and vibrational bands in a helium microhollow gas discharge

Majstorović

Jovović

Šišović

2017

Contrib. Plasma Phys

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Emission spectroscopy is applied to measure the gas temperature T g and the vibrational distribution of N2 (C 3Πu) and N2 +(B 2Σu +) excited states from a helium microhollow gas discharge (MHGD) at atmospheric pressure. The rotational temperature T rot of N2 + is determined from relative intensity of the R‐branch lines of the N2 +(B 2Σu +–X 2Σg +) bands at 427.81 and 419.91 nm and the well‐known Boltzmann plot (BP). Using the same diagnostic technique, the rotationally resolved N2(C 3Πu–B 3Πg) band at 380.49 nm is used to measure T rot. Under our experimental conditions, T g is equal to T rot = 550–650 K for nitrogen molecules and shows a slight increase with the discharge current in the current range 3–10 mA. From the intensity ratio of two consecutive vibrational bands of the same sequence, the N2(C 3Πu) and N2 +(B 2Σu +) vibrational temperature T vib = 3,700–4,000 K is determined. It has been found that N2 +(B 2Σu +) ions have non‐Boltzmann distribution in the helium MHGD, while N2(C 3Πu) molecules are populated according to the Boltzmann distribution. Following the Franck–Condon principle, the vibrational distribution of the ground state of N2(X 1Σg +) molecules has been determined from the N2(C 3Πu) distribution using the inversion matrix of elements q XC(ν,ν′).

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Experimental and theoretical study of the effect of gas flow on gas temperature in an atmospheric pressure microplasma

Cited by 89 publications

References 33 publications

Electron confinement and heating in microwave-sustained argon microplasmas

Electron confinement and heating in microwave-sustained argon microplasmas

Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

The analysis of nitrogen rotational and vibrational bands in a helium microhollow gas discharge

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