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Electron current extraction from radio frequency excited micro-dielectric barrier discharges
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10.1063/1.4775723
/content/aip/journal/jap/113/3/10.1063/1.4775723
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/3/10.1063/1.4775723
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Schematic of the cylindrical symmetric mDBD device. (a) Entire device and full computational domain. (b) Enlargement of mDBD cavity and location of sites A, B, C, and D that are used to provide surface properties and ionization characteristics.

Image of FIG. 2.
FIG. 2.

Time evolution of electron density (log scale, cm−3) and E/N (at the center of contour labels, Td) in the mDBD cavity at different phases of the rf driving voltage of 1.4 kV during a 40 ns (25 MHz) cycle. The cycle begins with 0 V on the buried rf electrode. The top electrode is biased with +2 kV. At high electron density, the electric field is shielded and E/N is reduced.

Image of FIG. 3.
FIG. 3.

Electron density in the plume (log scale, cm−3) in the gap at different phases of the rf driving voltage of 1.4 kV during a 40 ns (25 MHz) cycle.

Image of FIG. 4.
FIG. 4.

Electron temperature (eV), electron impact ionization sources from bulk electrons (Se ), and ionization source by sheath accelerated secondary electrons (Ssec ) in the mDBD cavity during a 40 ns (25 MHz) cycle for Vrf  = 1.4 kV and extraction voltage of 2 kV. The ionization sources are plotted on a log scale.

Image of FIG. 5.
FIG. 5.

The total charge density, charge density due to positive ions, and charge density due to electrons and negative ions (log scale cm−3) in the mDBD cavity at different times during a 25 MHz cycle for Vrf  = 1.4 kV and extraction voltage of 2 kV. Positive ions alternately strike the cathode-like negatively charged dielectric or discharge electrode and release secondary electrons for re-ignition.

Image of FIG. 6.
FIG. 6.

Density of excited states N2(C) and N2(A,B) in the mDBD cavity (log scale, cm−3) at different times during a 25 MHz cycle for Vrf  = 1.4 kV and extraction voltage of 2 kV. UV photons emitted from excited states of nitrogen produce secondary electrons which aid in re-ignition of the plasma especially at low frequency.

Image of FIG. 7.
FIG. 7.

The surface charge density σS (dashed-dotted, cm−3), surface voltage on the dielectric (solid, V), and voltage on the buried rf electrodes (dashed, V) are shown for frequencies of (a) 25, (b) 5, and (c) 2.5 MHz at site A (see Fig. 1 ) for Vrf  = 1.4 kV and extraction voltage of 2 kV. Oscillations in charging of the dielectric appear at low frequencies.

Image of FIG. 8.
FIG. 8.

mDBD characteristic are shown at site B as a function of time (see Fig. 1 ) for Vrf  = 1.4 kV and extraction voltage of 2 kV for (a) 25 MHz and (b) 2.5 MHz: rf voltage (dashed, V), local potential (dashed-dotted, V), and E/N (solid, Td), electron density (dashed-dotted, cm−3), and electron ionizations source Se and Ssec (solid and dotted, cm−3 s−1).

Image of FIG. 9.
FIG. 9.

rf potential (dashed, V) and collected current (solid, mA) for Vrf  = 1.4 kV and extraction voltage of 2 kV. (a) 25 MHz, (b) 15 MHz, (c) 5 MHz, and (d) 2.5 MHz. The current transitions from a single pulse to multiple pulses as the frequency decreases.

Image of FIG. 10.
FIG. 10.

Current collection on the top electrode. (a) Experimentally observed triple current pulsed obtained at 2.5 MHz and (b) simulation results in a similar sandwich mDBD device for equivalent biasing.

Image of FIG. 11.
FIG. 11.

Charge density at site D and current collection on the top electrode at 25 MHz. (a) Electron (solid, cm−3) and positive ion density (dashed, cm−3) at site D for top bias voltage Vtop = 2, 1.5, and 1 kV. (b) Electron current collected by the top biased electrode for Vtop = 2, 1.5, and 1 kV. A pulsed modulated dc current is collected at Vtop = 2 kV.

Image of FIG. 12.
FIG. 12.

Charge collection as a function of time for 25 MHz to 2.5 MHz (1.4 kV rf bias) and a 2 kV biased collection electrode. (a) Charge collected per pulse and (b) time integrated charge collection. Charge collection per pulse is relatively independent of frequency until positive charge builds up in the gap at the higher frequencies, which then transitions to a modulated dc discharge.

Image of FIG. 13.
FIG. 13.

Charge collection as a function of time for 25 MHz at Vrf  = 1.4, 2.8, 4.2, and 5.6 kV and a 2 kV biased collection electrode.

Image of FIG. 14.
FIG. 14.

Surface properties at site A and gas phase properties at site B as a function of time at 25 MHz for Vrf  = 1.4, 2.8, 4.2, and 5.6 kV. The location is noted in each frame. (a) Surface charge density and applied rf voltage, (b) surface potential, (c) E/N, (d) electron density, (e) ionization by bulk electrons, and (f) ionization by secondary electrons.

Image of FIG. 15.
FIG. 15.

Charge collection/pulse and total charge collected by the top 2 kV biased electrode as a function of time for 25 MHz with ε/ε0 = 20, 10, 5, and 2 with 1.4 kV on the rf electrode. The charge per pulse is normalized by εr = ε/ε0.

Image of FIG. 16.
FIG. 16.

Surface properties at site A and gas phase properties at sites B and C as a function of time at 25 MHz for ε/ε0 = 20, 10, 5, and 2. The location is noted in each frame. (a) Surface charge density normalized by εr and rf voltage, (b) surface potential, (c) E/N, (d) electron density, (e) ionization by bulk electrons, and (f) ionization by secondary electrons.

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/content/aip/journal/jap/113/3/10.1063/1.4775723
2013-01-16
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Electron current extraction from radio frequency excited micro-dielectric barrier discharges
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/3/10.1063/1.4775723
10.1063/1.4775723
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