... Authors: Nuno Pinhao (Nuclear and Technological Institute, Physics Dept., Sacavem, Portugal).... more ... Authors: Nuno Pinhao (Nuclear and Technological Institute, Physics Dept., Sacavem, Portugal).Mario Pinheiro (Lisbon Technical University, Physics Dept., Lisbon, Portugal). Zoltan Donko (Research Institute for Solid State Physics and Optics, Budapest, Hungary). ...
We have investigated the effect of constriction on the characteristics of low-pressure glow disch... more We have investigated the effect of constriction on the characteristics of low-pressure glow discharges in argon. In a series of experiments four discharge tubes with plane-parallel electrodes of different diameters (D = 31.4, 20, 10 and 5 mm) and same electrode separation (L0 = 45 mm) were studied. The discharges were surrounded by floating-potential metal tubes. We measured voltage-current characteristics
... Permissions & Reprints. Formation of CN x layers in a nitrogen glow discharge with graphi... more ... Permissions & Reprints. Formation of CN x layers in a nitrogen glow discharge with graphite electrodes. Kinga Kutasi a , Zoltán Donkó a , Miklós Mohai b , László Nemes Corresponding Author Contact Information , E-mail The Corresponding Author , b and György Marosi c. ...
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2000
Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for depositi... more Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for deposition of CNx layers were investigated in the visible range 350–900 nm. The spectra recorded at low and high resolution from both the negative glow and the positive column of the discharge were studied separately. All spectra are dominated by neutral and ionised N2 emission. In the positive column the violet band of the cyanogen (CN) radical was identified and analysed for vibrational structure. From a computer simulation of the rotationally resolved violet band, vibrational temperatures were derived and found to be in the intensity distribution for the v=0, 1 and 2 levels from thermal equilibrium. In the negative glow the strong N2+ features completely mask the spectral region of the violet band of CN. Conclusions were drawn concerning the CN formation by chemical sputtering, and the role of CN radicals in the formation of polymeric CNx layers of 1:1=C:N stoichiometry.
We report experimental and particle-based kinetic simulation studies of low-pressure capacitively... more We report experimental and particle-based kinetic simulation studies of low-pressure capacitively coupled oxygen plasmas driven by tailored voltage waveforms that consist of up to four harmonics of base frequency 13.56 MHz. Experimentally determined values of DC self-bias and electrical power deposition, as well as flux density and flux-energy distribution of the positive ions at the grounded electrode are compared with simulation data for a wide range of operating conditions. Very good agreement is found for self-bias and flux- energy distribution of the positive ions at the electrodes, while a fair agreement is reached for discharge power and ion flux data. The simulated spatial and temporal behaviour of the electric field, electron density, electron power absorption, ionization rate and mean electron energy shows a transition between sheath expansion heating and drift-ambipolar discharge modes, induced by changing either the number of harmonics comprising the excitation waveform or the gas pressure. The simulations indicate that under our experimental conditions the plasma operates at high electronegativity, and also reveal the crucial role of O2(a1∆g) singlet metastable molecules in establishing discharge behavior via the fast destruction of negative ions within the bulk plasma.
This paper intends to review some of the prominent properties of strongly coupled classical plasm... more This paper intends to review some of the prominent properties of strongly coupled classical plasmas having in mind the possible link with the quark-gluon plasma created in heavy-ion collisions. Thermodynamic and transport properties of classical liquid-state one-component plasmas are described and features of collective excitations are presented.
Charge dynamics in electrically asymmetric, geometrically symmetric dual frequency capacitively c... more Charge dynamics in electrically asymmetric, geometrically symmetric dual frequency capacitively coupled RF discharges operated at 13.56 MHz and 27.12 MHz with variable phase shift between the driving voltage waveforms is investigated experimentally as well as by a PIC simulation and analytical models. Via the Electrical Asymmetry Effect a variable DC self bias is generated as a function of the phase shift. Differences between the DC self bias resulting from simulation/experiment and analytical/fluid models at small phase angles are explained by the charge dynamics within one low frequency RF period (not taken into account in the models). Depending on phase shift and pressure the excitation at the powered electrode is stronger or weaker compared to the grounded electrode (asymmetric excitation). The excitation dynamics is different at high (100 Pa) and low pressures (3 Pa): at low/high pressure the excitation is asymmetric at phase shifts of strong/weak DC self bias, respectively. Th...
In a classical ideal plasma, a magnetic field is known to reduce the heat conductivity perpendicu... more In a classical ideal plasma, a magnetic field is known to reduce the heat conductivity perpendicular to the field whereas it does not alter the one along the field. Here we show that, in strongly correlated plasmas that are observed at high pressure or/and low temperature, a magnetic field reduces the perpendicular heat transport much less and even {\it enhances} the parallel transport. These surprising observations are explained by the competition of kinetic, potential and collisional contributions to the heat conductivity. Our results are based on first principle molecular dynamics simulations of a one-component plasma.
The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the ... more The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the electron heating dynamics in capacitively coupled radio-frequency (CCRF) plasmas. In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, we investigate the self-excitation of PSR oscillations and their effect on the electron heating in geometrically symmetric CCRF plasmas driven by multiple consecutive harmonics. The discharge symmetry is controlled via the electrical asymmetry effect (EAE), i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations will be self-excited under both symmetric and asymmetric conditions, if (i) the charge–voltage relation of the plasma sheaths deviates from a simple quadratic behavior and (ii) the inductance of the plasma bulk exhibits a temporal modulation. These two effects have been neglected up to now, but we show that they must be include...
... Authors: Nuno Pinhao (Nuclear and Technological Institute, Physics Dept., Sacavem, Portugal).... more ... Authors: Nuno Pinhao (Nuclear and Technological Institute, Physics Dept., Sacavem, Portugal).Mario Pinheiro (Lisbon Technical University, Physics Dept., Lisbon, Portugal). Zoltan Donko (Research Institute for Solid State Physics and Optics, Budapest, Hungary). ...
We have investigated the effect of constriction on the characteristics of low-pressure glow disch... more We have investigated the effect of constriction on the characteristics of low-pressure glow discharges in argon. In a series of experiments four discharge tubes with plane-parallel electrodes of different diameters (D = 31.4, 20, 10 and 5 mm) and same electrode separation (L0 = 45 mm) were studied. The discharges were surrounded by floating-potential metal tubes. We measured voltage-current characteristics
... Permissions & Reprints. Formation of CN x layers in a nitrogen glow discharge with graphi... more ... Permissions & Reprints. Formation of CN x layers in a nitrogen glow discharge with graphite electrodes. Kinga Kutasi a , Zoltán Donkó a , Miklós Mohai b , László Nemes Corresponding Author Contact Information , E-mail The Corresponding Author , b and György Marosi c. ...
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2000
Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for depositi... more Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for deposition of CNx layers were investigated in the visible range 350–900 nm. The spectra recorded at low and high resolution from both the negative glow and the positive column of the discharge were studied separately. All spectra are dominated by neutral and ionised N2 emission. In the positive column the violet band of the cyanogen (CN) radical was identified and analysed for vibrational structure. From a computer simulation of the rotationally resolved violet band, vibrational temperatures were derived and found to be in the intensity distribution for the v=0, 1 and 2 levels from thermal equilibrium. In the negative glow the strong N2+ features completely mask the spectral region of the violet band of CN. Conclusions were drawn concerning the CN formation by chemical sputtering, and the role of CN radicals in the formation of polymeric CNx layers of 1:1=C:N stoichiometry.
We report experimental and particle-based kinetic simulation studies of low-pressure capacitively... more We report experimental and particle-based kinetic simulation studies of low-pressure capacitively coupled oxygen plasmas driven by tailored voltage waveforms that consist of up to four harmonics of base frequency 13.56 MHz. Experimentally determined values of DC self-bias and electrical power deposition, as well as flux density and flux-energy distribution of the positive ions at the grounded electrode are compared with simulation data for a wide range of operating conditions. Very good agreement is found for self-bias and flux- energy distribution of the positive ions at the electrodes, while a fair agreement is reached for discharge power and ion flux data. The simulated spatial and temporal behaviour of the electric field, electron density, electron power absorption, ionization rate and mean electron energy shows a transition between sheath expansion heating and drift-ambipolar discharge modes, induced by changing either the number of harmonics comprising the excitation waveform or the gas pressure. The simulations indicate that under our experimental conditions the plasma operates at high electronegativity, and also reveal the crucial role of O2(a1∆g) singlet metastable molecules in establishing discharge behavior via the fast destruction of negative ions within the bulk plasma.
This paper intends to review some of the prominent properties of strongly coupled classical plasm... more This paper intends to review some of the prominent properties of strongly coupled classical plasmas having in mind the possible link with the quark-gluon plasma created in heavy-ion collisions. Thermodynamic and transport properties of classical liquid-state one-component plasmas are described and features of collective excitations are presented.
Charge dynamics in electrically asymmetric, geometrically symmetric dual frequency capacitively c... more Charge dynamics in electrically asymmetric, geometrically symmetric dual frequency capacitively coupled RF discharges operated at 13.56 MHz and 27.12 MHz with variable phase shift between the driving voltage waveforms is investigated experimentally as well as by a PIC simulation and analytical models. Via the Electrical Asymmetry Effect a variable DC self bias is generated as a function of the phase shift. Differences between the DC self bias resulting from simulation/experiment and analytical/fluid models at small phase angles are explained by the charge dynamics within one low frequency RF period (not taken into account in the models). Depending on phase shift and pressure the excitation at the powered electrode is stronger or weaker compared to the grounded electrode (asymmetric excitation). The excitation dynamics is different at high (100 Pa) and low pressures (3 Pa): at low/high pressure the excitation is asymmetric at phase shifts of strong/weak DC self bias, respectively. Th...
In a classical ideal plasma, a magnetic field is known to reduce the heat conductivity perpendicu... more In a classical ideal plasma, a magnetic field is known to reduce the heat conductivity perpendicular to the field whereas it does not alter the one along the field. Here we show that, in strongly correlated plasmas that are observed at high pressure or/and low temperature, a magnetic field reduces the perpendicular heat transport much less and even {\it enhances} the parallel transport. These surprising observations are explained by the competition of kinetic, potential and collisional contributions to the heat conductivity. Our results are based on first principle molecular dynamics simulations of a one-component plasma.
The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the ... more The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the electron heating dynamics in capacitively coupled radio-frequency (CCRF) plasmas. In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, we investigate the self-excitation of PSR oscillations and their effect on the electron heating in geometrically symmetric CCRF plasmas driven by multiple consecutive harmonics. The discharge symmetry is controlled via the electrical asymmetry effect (EAE), i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations will be self-excited under both symmetric and asymmetric conditions, if (i) the charge–voltage relation of the plasma sheaths deviates from a simple quadratic behavior and (ii) the inductance of the plasma bulk exhibits a temporal modulation. These two effects have been neglected up to now, but we show that they must be include...
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Papers by Zoltan Donko
wide range of operating conditions. Very good agreement is found for self-bias and flux- energy distribution of the positive ions at the electrodes, while a fair agreement is reached
for discharge power and ion flux data. The simulated spatial and temporal behaviour of the electric field, electron density, electron power absorption, ionization rate and mean electron energy shows a transition between sheath expansion heating and drift-ambipolar discharge modes, induced by changing either the number of harmonics comprising the excitation waveform or the gas pressure. The simulations indicate that under our experimental conditions the plasma operates at high electronegativity, and also reveal the crucial role of O2(a1∆g) singlet metastable molecules in establishing discharge behavior via the fast destruction of negative ions within the bulk plasma.
wide range of operating conditions. Very good agreement is found for self-bias and flux- energy distribution of the positive ions at the electrodes, while a fair agreement is reached
for discharge power and ion flux data. The simulated spatial and temporal behaviour of the electric field, electron density, electron power absorption, ionization rate and mean electron energy shows a transition between sheath expansion heating and drift-ambipolar discharge modes, induced by changing either the number of harmonics comprising the excitation waveform or the gas pressure. The simulations indicate that under our experimental conditions the plasma operates at high electronegativity, and also reveal the crucial role of O2(a1∆g) singlet metastable molecules in establishing discharge behavior via the fast destruction of negative ions within the bulk plasma.