Dusty discharges with secondary electron emission
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| Date: | 2002 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Cite this: | Dusty discharges with secondary electron emission / Yu.I. Chutov, W.J. Goedheer, O.Yu. Kravchenko, O.A. Lavrov, R. Romanenko // Вопросы атомной науки и техники. — 2002. — № 4. — С. 168-169. — Бібліогр.: 8 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859717819365588992 |
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| author | Chutov, Yu. I. Goedheer, W.J. Kravchenko, O.Yu. Lavrov, O.A. Romanenko, R. |
| author_facet | Chutov, Yu. I. Goedheer, W.J. Kravchenko, O.Yu. Lavrov, O.A. Romanenko, R. |
| citation_txt | Dusty discharges with secondary electron emission / Yu.I. Chutov, W.J. Goedheer, O.Yu. Kravchenko, O.A. Lavrov, R. Romanenko // Вопросы атомной науки и техники. — 2002. — № 4. — С. 168-169. — Бібліогр.: 8 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| first_indexed | 2025-12-01T08:33:14Z |
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DUSTY DISCHARGES WITH SECONDARY ELECTRON EMISSION
Yu. I. Chutov, W.J. Goedheer*, O.Yu. Kravchenko, O.A. Lavrov, R.Romanenko
Taras Shevchenko Kiev University, Kiev, Ukraine
* FOM-Institute for Plasma Physics "Rijnhuizen", Nieuwegein, The Netherlands
PACS: 52.27.Lw
INTRODUCTION
There are two main regimes of RF discharges [1,2]
called the α – regime and γ - regime. They differ by the
role of a secondary emission from electrodes or walls. RF
discharges are supported mainly by a volume ionization
in the α – regime unlike the γ - regime where the
secondary emission is important for the discharge
support. The α – regime is realized at a relatively high
pressure, the γ - regime at a low pressure.
Although RF discharges with secondary emission were
investigated earlier, the role of the secondary emission in
the discharges is not yet clear. The main difficulty arises
from the necessary to take into account (self-consistently
with discharge parameters) all kinds of secondary
electrons emitted from the electrodes (walls) by ion,
electron, fast atom, or metastable impact as well as by
ultraviolet radiation from the discharge. Recently, models
of the effective secondary-emission yield γ per ion were
developed for the breakdown [3] and DC glow discharges
[4] in argon. The models take into account all kinds of
secondary electrons and give the dependence of the
effective yield γ on the cathode electric field reduced by
the argon atom density. These models can be useful for
RF discharges.
Dust particles can appear in RF discharges as the
product of the plasma-wall interaction with their
subsequent transport into an interelectrode space or can
be created due to coagulation of various components in
chemically active plasmas. It is known [5,6] that the dust
particles can essentially influence the parameters of the
RF discharges due to a continuous selective collection of
background electrons and ions that can essentially
influence their energy distribution functions. Dusty RF
discharges with secondary electrons were not investigated
earlier, although it is obvious that secondary emission has
to influence the properties of dusty discharges especially
at low pressures when the role of secondary electrons is
growing. The computer simulation of dusty RF discharges
with secondary electrons is the aim of the work.
MODEL
A one-dimensional RF discharge is considered
between two plane electrodes separated by a gap of d =
2.0 cm which is filled with Ar at various pressures.
Immobile dust particles of a given radius Rd are
distributed uniformly in the interelectrode gap with a
density Nd. The dust particles collect and scatter electrons
and ions distributed in the discharge with density ne and
ni, respectively. A harmonic external voltage
Ve(t)=Vosin(wt) at a frequency f=13,56 MHz and various
amplitudes Vo sustains the RF discharge. The discharge is
grounded at x=d.
The PIC/MCC method described in detail earlier for
discharges without dust particles is developed for
computer simulations of the RF discharge with dust
particles. The Monte Carlo technique is used to describe
electron and ion collisions. The collisions include elastic
collisions of electrons and ions with atoms, ionization and
excitation of atoms by electrons, charge exchange
between ions and atoms, Coulomb collisions of electrons
and ions with dust particles, as well as the electron and
ion collection and scattering by dust particles. In addition
to a usual PIC/MCC scheme, the weighting procedure is
used also for the determination of a superparticle charge
part, which is interacting with a dust particle.
The electron-argon collision cross-sections used in the
model are the same as those used in [7]. The Coulomb
cross-section for electron and ion scattering by immobile
dust particles is taken from [8]. The secondary emission is
taken into account in the framework of the models of
[3,4] or at given various constant yields γ of the effective
secondary emission.
The simulation starts at an initial uniform distribution
of electrons and ions with given densities and is
prolonged by iterations up to a moment when a change of
discharge parameters is less a given limit. Simulation
shows that 400-1000 cycles are enough to obtain the
periodically steady state of RF discharges.
RESULTS
Obtained spatial distributions of the electron ne and ion
ni densities across the interelectrode gap are shown in Fig.
1 for various phases ϕ of the sustaining external voltage
Fig. 1. Spatial distributions of the electron ne and ion
ni density.
with an amplitude of V=100 V. The distributions are
obtained at a dust particle density Nd=3*1011 m-3, a dust
particle radius Rd = 1 µm, and an effective secondary
electron emission yields γ = G1 corresponding to the
model [3]. Note, the distributions of the ion density
shown here by solid lines are the same for various phases
168 Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 168-169
0.0 0.5 1.0
0
2
4
6
Nd=3*1011 m-3
γ = G1
n*10-15, m-3
ni,
ne, ϕ = 0
ne, ϕ = π /2
ne, ϕ = 3π /2
x/d
ϕ unlike the electron density distributions which are
different close to electrodes. As can be seen in Fig. 1, the
electron density distributions are the same in the central
part of the interelectrode gap for various phases ϕ
however there is a difference between electron and ion
densities due to the space charge of the dust particles,
similar to [5,6]. The distributions show the existence of
the central quasi-neutral region (with taking into account
the total dust particles charge) and non-neutral RF sheaths
close to both electrodes like in the case of the RF
discharge without the secondary emission [5,6].
The influence of the secondary emission on the dusty
RF discharge can be seen in Fig.2 where spatial
Fig. 2. Spatial distributions of the ion ni density for
various γ and V.
distributions of the ion density, ni are plotted for various
combinations of the effective secondary-emission yield γ
and the amplitude Vo of the harmonic external voltage.
Fig. 2 shows that the increase of γ causes an essential
increase of the ion density in the central part of the
discharge at Vo = const whereas the ion density is
practically unchanged in sheaths. The density increase is
caused by an additional ionization in the central discharge
part by secondary electrons whereas the ion shielding of
the given applied voltage causes the invariability of the
ion density distributions in sheaths. As can be seen in
Fig.2, the remarkable influence of the secondary emission
on the discharge parameters takes place only at γ > 0.2.
Note, the discharge parameters obtained in the framework
of the model [4] (γ = G2) does not differ from the
parameters in the discharge without the secondary
emission because the effective secondary-emission yields
γ in the model [4] is less than γ = 0.2. The model [3]
provides a very strong increase of the ion density in the
central discharge part because the model gives an
effective secondary-emission yield γ that can amount to
high values.
Spatial distributions of the dust particle charge qd are
shown in Fig. 3 for the conditions of Fig. 2. As can be
seen in Fig. 3, the charge qd depends very weakly on the
yield γ at Vo= 365 V unlike the ion ni density shown in
Fig. 2. It is a typical result for intensive RF discharges
and is caused by the dust particle charging in low-
pressure RF discharges considered earlier in [5,6]. There
it was shown that non-monotonic profiles of the dust
particle charge in RF discharges are caused by the change
of the ion current into a dust particle in non-uniform
quasi-neutral plasma with omnipresent fast electrons due
to their fast penetration in regions wit low electric fields.
Fig. 3. Spatial distributions of the dust particle charge qd..
The simulations of RF discharges with secondary
emission show that the ratio of the electron and ion
currents into a dust particle is approximately conserved
while changing the effective secondary-emission yields γ
in intensive RF discharges. This causes the invariability
of dust charge distributions. Typical examples of spatial
distributions of the dust particle charge qd for low-power
RF discharges are shown in Fig. 3 in the case of Vo=100
V. As can be seen in this case, the secondary emission
changes the negative charge of a dust particle in the quasi-
neutral central part of the discharge compared to the high-
power RF discharge. However, like in the high-power RF
discharges, the change of the yield γ does not result in a
change of the spatial distributions.
CONCLUSION
In conclusion, dusty RF discharges are simulated by
using the PIC/MCC method. Secondary electron emission
is taken into account in the framework of the of the
effective yields developed earlier. It is shown that the
secondary emission essentially influence the electron and
ion densities in the discharges due to more intensive
ionization caused by secondary electrons. However the
dust particle charge is conserved at the change of the
secondary emission due to a specific charging of dust
particles.
ACKNOWLEDGMENT
This work was partially supported by INTAS and by a
grant from the Ukrainian Ministry of Education and
Science.
REFERENCES
1. Lieberman M.A., Lichtenberg A.J. Principles of Plasma Discharges
and Material Processing, Wiley, New York, 1994, pp. 1-19
2. Levitskij S.M. Zh. Tekh. Fiz. 27 1001-1109 (1957). (in Russian)
3. Phelps A.V., Petrovic Z .Lj. Plasma Sources Sci. Technol., 8. R21–
R44 (1999).
4. Donko Z. Phys. Rev. E, 64 7420-7425 (2001).
5. Chutov Yu.I.., Goedheer W.J., Kravchenko O.Yu., Zuz V.M., Yan
M. Materials Science Forum: Plasma Processing and Dusty
Particles, 382 69-79 (2001).
6. Chutov Yu., Goedheer W., Kravchenko O., Zuz V., Yan M.. J.
Plasma and Fusion Research. SERIES, 4 340-344 (2001)
7. Surendra M., Graves D.B., Jellum G.M. Phys. Rev., A 41 1012-1014
(1990)
169
0.0 0.5 1.0
0
2
4
6
0. 0 0 . 5 1 .00
1
2
Vo=-100 V
γ = 0.0
γ = G2
γ = 0.3
γ = 0.5
γ = G1
ni*10-15, m-3
x/d
Vo = -365 V
Nd=1*1011 m-3
γ = 0.0
γ = G2
γ = 0.3
γ = G1
ni*10-16, m-3
x /d
0.0 0.5 1.0
0.0
0.5
0. 0 0. 5 1. 0
0.0
0.5
V=-100 V
γ=0.0 γ=0.5
γ=0.3 γ=1.0
-qd*10-3/e
x/d
V=-365 V
γ=0.0 γ=G-1
γ=0.3
-qd*103/e
x /d
8. Trubnikov B.A. In: Problems of plasma theory, 1 122-124 (1963).
(in Russian)
170
Taras Shevchenko Kiev University, Kiev, Ukraine
INTRODUCTION
MODEL
RESULTS
CONCLUSION
ACKNOWLEDGMENT
REFERENCES
|
| id | nasplib_isofts_kiev_ua-123456789-80326 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-01T08:33:14Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| spelling | Chutov, Yu. I. Goedheer, W.J. Kravchenko, O.Yu. Lavrov, O.A. Romanenko, R. 2015-04-14T18:30:56Z 2015-04-14T18:30:56Z 2002 Dusty discharges with secondary electron emission / Yu.I. Chutov, W.J. Goedheer, O.Yu. Kravchenko, O.A. Lavrov, R. Romanenko // Вопросы атомной науки и техники. — 2002. — № 4. — С. 168-169. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 52.27.Lw https://nasplib.isofts.kiev.ua/handle/123456789/80326 This work was partially supported by INTAS and by a grant from the Ukrainian Ministry of Education and Science. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Low temperature plasma and plasma technologies Dusty discharges with secondary electron emission Article published earlier |
| spellingShingle | Dusty discharges with secondary electron emission Chutov, Yu. I. Goedheer, W.J. Kravchenko, O.Yu. Lavrov, O.A. Romanenko, R. Low temperature plasma and plasma technologies |
| title | Dusty discharges with secondary electron emission |
| title_full | Dusty discharges with secondary electron emission |
| title_fullStr | Dusty discharges with secondary electron emission |
| title_full_unstemmed | Dusty discharges with secondary electron emission |
| title_short | Dusty discharges with secondary electron emission |
| title_sort | dusty discharges with secondary electron emission |
| topic | Low temperature plasma and plasma technologies |
| topic_facet | Low temperature plasma and plasma technologies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/80326 |
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