The Experts below are selected from a list of 3657 Experts worldwide ranked by ideXlab platform
Deborah Oconnell - One of the best experts on this subject based on the ideXlab platform.
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strong ionization asymmetry in a geometrically symmetric radio frequency capacitively coupled plasma induced by sawtooth voltage waveforms
Physical Review Letters, 2015Co-Authors: Bastien Bruneau, Deborah Oconnell, Timo Gans, Arthur Greb, E V Johnson, Jeanpaul BoothAbstract:The ionization dynamics in geometrically symmetric parallel plate capacitively coupled plasmas driven by radio frequency tailored voltage waveforms is investigated using phase resolved optical emission spectroscopy (PROES) and particle-in-cell (PIC) simulations. Temporally asymmetric waveforms induce spatial asymmetries and offer control of the spatiotemporal dynamics of electron heating and associated ionization structures. Sawtooth waveforms with different rise and fall rates are employed using truncated Fourier series approximations of an ideal sawtooth. Experimental PROES results obtained in argon plasmas are compared with PIC simulations, showing excellent agreement. With waveforms comprising a fast voltage drop followed by a slower rise, the faster sheath expansion in front of the Powered Electrode causes strongly enhanced ionization in this region. The complementary waveform causes an analogous effect in front of the grounded Electrode.
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electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet
Applied Physics Letters, 2011Co-Authors: Th Q Algwari, Deborah OconnellAbstract:The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the Powered and grounded Electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the Powered Electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded Electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.
Joachim Janes - One of the best experts on this subject based on the ideXlab platform.
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angular characteristics of argon ion fluxes at the rf Powered Electrode of a parallel plate reactor
Microelectronic Engineering, 1995Co-Authors: Karla Bornig, Joachim JanesAbstract:In a parallel-plate 13.56 MHz rf reactor argon ions are created in a plasma and are accelerated by the electric field across the sheath where they are subject to charge-exchange collisions and elastic scattering. The time-dependent electric field and the sheath length are used as input for Monte Carlo simulations. Assuming initial trajectories for ions crossing the plasma sheath boundary deviating from being parallel to the sheath electric field, secondary maxima in the ion angular distributions are found. Experimental ion angular distributions are investigated by sampling ions through a 100 μm orifice. These ions are detected with a quadrupole mass spectrometer which is tilted with the vertex lying in the orifice. The experimental ion angular distributions are compared with the results of Monte Carlo simulations showing that experimental and simulated distributions are in fairly good correspondence.
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angular impact energy distributions of argon ions at the Powered Electrode of a helicon plasma source
Journal of Vacuum Science and Technology, 1994Co-Authors: Joachim JanesAbstract:A radio frequency excited helicon plasma is generated by coupling externally generated electric and magnetic fields into the plasma confined by an axial magnetic field. The 13.56 MHz rf power provided via an antenna is varied between 100 and 500 W. The axial magnetic field strength is varied between 25 and 150 G. The substrate Electrode is independently Powered with 13.56 MHz radio frequency. A 100 μm orifice in the substrate Electrode allows a small sample of argon ions bombarding the substrate Electrode to enter a detection chamber. In the detection chamber a quadrupole mass spectrometer equipped with an energy filter is used to measure mass selected ion energy distributions and by tilting the quadrupole analyzer with the vertex lying in the orifice ion angular distributions are investigated. The ion energy distributions at the Powered Electrode mainly consist of either a single peak or they consist of the well known bimodal structure caused by rf splitting. For some source parameter a continuous energy...
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mass selected ion angular impact energy distributions at the Powered Electrode in cf4 reactive ion etching
Journal of Applied Physics, 1993Co-Authors: Joachim JanesAbstract:The ion energy distributions and ion angular distributions of CF+, CF+2, and CF+3 currents were measured at the Powered Electrode of a capacitively coupled 13.56 MHz discharge parallel‐plate reactor running on CF4. The pressure range is varied between 5 and 50 mTorr, and by adjusting the rf power dissipated in the plasma the dc bias potential at the cathode is varied between −150 and −450 V. Ions are sampled through a small orifice in an aluminum wafer bonded to the cathode. Downstream the orifice ions are selected in a quadrupole mass spectrometer equipped with an energy filter. Tilting this detection system with the vertex lying in the orifice ion angular distributions are measured. The ion energy distributions were found to exhibit structures which appear as continua. The structures result from collision processes of CF+x (x=1–3) with the CF4 parent gas in the sheath. Charge‐exchange collisions could be identified neither in the ion energy distributions nor in the ion angular distributions. The ion ang...
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energy distributions of argon neutrals at the rf Powered Electrode of a parallel plate reactor
Journal of Applied Physics, 1993Co-Authors: Joachim Janes, Karla BornigAbstract:In a parallel‐plate 13.56 MHz rf reactor energetic argon neutrals are created by charge‐exchange collisions in the sheath adjacent to the Powered Electrode. Energetic argon neutrals are detected by sampling neutrals through a 100 μm orifice in the cathode. Downstream the orifice neutrals are analyzed parallel to the cathode normal with a quadrupole mass spectrometer equipped with an energy filter having an angular acceptance of about 2.5°. The pressure range considered was between 5 and 50 mTorr with dc bias potentials between −100 and −400 V. The measured neutral energy distributions for low pressures and low dc bias potentials have a maximum intensity at low energies slowly decreasing toward higher energies. For higher pressures and higher dc bias potentials the energy distributions have minimal intensities at low energies, exhibit a maximum at roughly 40 eV, subsequently decreasing toward higher energies. This behavior is explained as being caused by multiple scattering of energetic neutrals in the she...
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energy resolved angular distributions of o ions at the radio frequency Powered Electrode in reactive ion etching
Journal of Vacuum Science and Technology, 1992Co-Authors: Joachim Janes, Christoph HuthAbstract:Mass‐selected distributions of bombardment energies of O+ ions at the Powered Electrode of a reactive ion etcher are investigated under angles between ±10° with respect to the Electrode normal. The energy distributions consist of split high‐energy peaks and continuous intensities between 50 eV and the maximal energy defined by the potential drop across the sheath. Ions found in the bimodal split high‐energy peaks show angular distributions with widths between 2° and 6° [full width at half‐maximum (FWHM)]. The continuous part of the ion energy distributions exhibit angular widths between 7° and 11° (FWHM). The observed phenomena in the ion energy and ion angular distributions are interpreted as combined effects of elastic scattering and dissociative collisions in the sheath.
Amanda M Lietz - One of the best experts on this subject based on the ideXlab platform.
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Electrode configurations in atmospheric pressure plasma jets production of reactive species
Plasma Sources Science and Technology, 2018Co-Authors: Amanda M LietzAbstract:Atmospheric pressure plasma jets (APPJs) are a preferred plasma source for many biomedical applications. These jets typically consist of a rare gas flowing through a dielectric tube, possibly with an O2 or H2O admixture, and flowing into the ambient. They are typically Powered by pulsed or sinusoidal voltage waveforms. However, in most other aspects APPJ designs differ greatly. In this paper, APPJ design parameters and their consequences on ionization wave (IW) propagation and reactive oxygen and nitrogen species (RONS) production are discussed using results from a two-dimensional plasma hydrodynamics model. The base case is an APPJ with a single Powered ring Electrode wrapped around a dielectric tube. This configuration was varied by adding a grounded ring Electrode, changing the Powered and grounded Electrode positions, and moving the Powered Electrode to the inside of the tube. Placing the Powered Electrode closer to the outlet of the tube increased the RONS production by increasing the energy deposition outside the tube. Adding a grounded ring increased the IW intensity inside the tube while slightly increasing the power deposition outside of the tube. An inner Powered Electrode increased the IW intensity and propagation velocity, and the resulting RONS production. Co-axial ground planes within 5 cm of the APPJ significantly affected the IW behavior, increasing its intensity and increasing RONS production. The consequences of voltage rise time and dielectric constant of the tube are also discussed. The systematic trends from this investigation may facilitate more informed APPJ design choices that may be tailored to the goals of a specific application.
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plasma induced flow instabilities in atmospheric pressure plasma jets
Applied Physics Letters, 2017Co-Authors: Amanda M Lietz, Eric JohnsenAbstract:Pulsed plasma excitation of rare gases flowing into air has been shown to impact the stability of the flow in non-equilibrium atmospheric pressure plasma jets (APPJs). In this paper, the results from a numerical modeling investigation of the stability of a round He APPJ with a Powered Electrode exposed to the gas flow are discussed. Localized gas heating at the Powered Electrode occurs on the time scale of the voltage pulse, tens to 100 ns, which is short compared to the fluid timescales. An acoustic wave propagates from this heated, expanding gas and exits the jet. The wave disturbs the shear layer between the He and surrounding humid air, exciting a shear instability which grows downstream with the flow and increases the mixing of the humid air into the He. The effects of the eddy-dominated flow on ionization wave (IW) propagation in an APPJ were investigated. The IW followed the regions of the highest helium concentration, resulting in an increased production of NO, HO2, and NO2.
Th Q Algwari - One of the best experts on this subject based on the ideXlab platform.
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electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet
Applied Physics Letters, 2011Co-Authors: Th Q Algwari, Deborah OconnellAbstract:The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the Powered and grounded Electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the Powered Electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded Electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.
Tsutomu Tsukada - One of the best experts on this subject based on the ideXlab platform.
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evaluation of self bias potential distribution on a Powered Electrode of supermagnetron plasma apparatus
Journal of Applied Physics, 1999Co-Authors: Haruhisa Kinoshita, Shyuji Nomura, Yukito Nakagawa, Tsutomu TsukadaAbstract:The distribution of self-bias potential (Vdc) on a Powered Electrode of a supermagnetron plasma system, where both Electrodes are supplied phase-shifted radio frequency (rf) currents, was measured using five electrical probes buried in the Electrode. For comparison, the same was measured for a conventional magnetron plasma system. Measurements were carried out with an Ar discharge at the pressure region of 4–50 mTorr. The data obtained with the supermagnetron and the conventional magnetron plasm systems were used to map the Vdc distribution on the Powered Electrodes of each plasma source. When the phase difference between rf currents applied to the two parallel Electrodes of supermagnetron plasma system were changed, a drastic change of the Vdc is observed. The uniformity of the Vdc distribution is greatly improved when the phase difference between rf currents is varied from 0° to about 180°. The further increase of phase difference between two rf currents causes a decrease of the uniformity of the Vdc di...
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influence of magnetic field on the self bias potential on a radio frequency Powered Electrode in radio frequency plasma
Journal of Vacuum Science and Technology, 1993Co-Authors: K Tsuzuki, Yukito Nakagawa, S Tabuchi, Tatsuya Banno, Akira Kinbara, Tsutomu TsukadaAbstract:Electric self‐bias potential and its distribution on the radio frequency (rf) Electrode in an rf plasma have been measured using probes buried in the Electrode. The potential increases almost proportionally with the net rf power (Wrf) ranging from 5 to 80 W. When the magnetic field parallel to the Electrode (Wrf=26 W) is applied, the potential is reduced from −150 V (0 T) to −50 V (0.04 T) at the center of the Electrode and the gradient in the potential distribution occurs along the E×B direction. This mechanism, the role of the external magnetic field, and the industrial applicability are discussed.