Influence of dust particles on RF-discharge plasma afterglow
In this paper we report about results of computer simulation by PIC/MCC method of the discharging of dust particles in the plasma afterglow and time dependence of plasma parameters in discharge gap after switching off the voltage. It is shown that discharging of dust particles in the afterglow plasm...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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irk-123456789-822572015-05-28T03:02:11Z Influence of dust particles on RF-discharge plasma afterglow Kravchenko, O.Yu. Maruschak, I.S. Yushchyshena, Yu.V. Низкотемпературная плазма и плазменные технологии In this paper we report about results of computer simulation by PIC/MCC method of the discharging of dust particles in the plasma afterglow and time dependence of plasma parameters in discharge gap after switching off the voltage. It is shown that discharging of dust particles in the afterglow plasma after switching off voltage of radiofrequency discharge occurs faster in the central part of the electrode gap due to the ion cloud forming and intense recombination of electrons in collisions with dust particles in this area. Moreover, the discharging rate is increasing with increasing of the dust particles density. In the initial stage after the switching off the voltage plasma has a positive potential relative to the electrodes. Eventually, when the electron and ion densities are significantly reduced, the charge of the plasma is determined by the amount of negative dust particles. In this case, the plasma potential is negative relative to the electrodes, which contributes to the effective diffusion of dust particles on the walls of the discharge chamber. Представлены результаты компьютерного моделирования методом PIC/MCC разрядки пылевых частиц в послесвечении плазмы радиочастотного разряда и временные зависимости параметров плазмы в разрядном промежутке после выключения напряжения. Показано, что разрядка пылевых частиц в послесвечении плазмы после выключения напряжения радиочастотного разряда происходит быстрее в центральной части межэлектродного промежутка, что обусловлено образованием ионного сгустка и интенсивной рекомбинацией электронов при столкновении с пылинками в этой области. Кроме того, скорость разрядки увеличивается с увеличением плотности частиц пыли. В начальной стадии после выключения напряжения плазма имеет положительный потенциал относительно электродов. В конце концов, когда концентрации электронов и ионов значительно снижаются, заряд плазмы определяется количеством отрицательных частиц пыли. В этом случае потенциал плазмы является отрицательным по отношению к электродам. Представлено результати комп'ютерного моделювання методом PIC/MCC розрядки пилових частинок у післясвітінні плазми радіочастотного розряду та часові розподіли параметрів плазми в розрядному проміжку після вимкнення напруги. Показано, що розрядка пилових частинок у післясвітінні плазми після вимкнення напруги радіочастотного розряду відбувається швидше в центральній частині міжелектродного проміжку, що пов’язано з утворенням іонного згустка та інтенсивною рекомбінацією електронів при зіткненні з пилинками в цій області. Крім того, швидкість розрядки збільшується зі збільшенням концентрації частинок пилу в розряді. На початковій стадії після вимкнення напруги плазма має позитивний потенціал щодо електродів. Зрештою, коли концентрації електронів та іонів значно знижуються, заряд плазми визначається кількістю негативних частинок пилу. У цьому випадку потенціал плазми є негативним по відношенню до електродів. 2015 Article Influence of dust particles on RF-discharge plasma afterglow / O.Yu. Kravchenko, I.S. Maruschak, Yu.V. Yushchyshena // Вопросы атомной науки и техники. — 2015. — № 1. — С. 220-223. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.27.Lw. http://dspace.nbuv.gov.ua/handle/123456789/82257 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| topic |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии |
| spellingShingle |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии Kravchenko, O.Yu. Maruschak, I.S. Yushchyshena, Yu.V. Influence of dust particles on RF-discharge plasma afterglow Вопросы атомной науки и техники |
| description |
In this paper we report about results of computer simulation by PIC/MCC method of the discharging of dust particles in the plasma afterglow and time dependence of plasma parameters in discharge gap after switching off the voltage. It is shown that discharging of dust particles in the afterglow plasma after switching off voltage of radiofrequency discharge occurs faster in the central part of the electrode gap due to the ion cloud forming and intense recombination of electrons in collisions with dust particles in this area. Moreover, the discharging rate is increasing with increasing of the dust particles density. In the initial stage after the switching off the voltage plasma has a positive potential relative to the electrodes. Eventually, when the electron and ion densities are significantly reduced, the charge of the plasma is determined by the amount of negative dust particles. In this case, the plasma potential is negative relative to the electrodes, which contributes to the effective diffusion of dust particles on the walls of the discharge chamber. |
| format |
Article |
| author |
Kravchenko, O.Yu. Maruschak, I.S. Yushchyshena, Yu.V. |
| author_facet |
Kravchenko, O.Yu. Maruschak, I.S. Yushchyshena, Yu.V. |
| author_sort |
Kravchenko, O.Yu. |
| title |
Influence of dust particles on RF-discharge plasma afterglow |
| title_short |
Influence of dust particles on RF-discharge plasma afterglow |
| title_full |
Influence of dust particles on RF-discharge plasma afterglow |
| title_fullStr |
Influence of dust particles on RF-discharge plasma afterglow |
| title_full_unstemmed |
Influence of dust particles on RF-discharge plasma afterglow |
| title_sort |
influence of dust particles on rf-discharge plasma afterglow |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2015 |
| topic_facet |
Низкотемпературная плазма и плазменные технологии |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/82257 |
| citation_txt |
Influence of dust particles on RF-discharge plasma afterglow / O.Yu. Kravchenko, I.S. Maruschak, Yu.V. Yushchyshena // Вопросы атомной науки и техники. — 2015. — № 1. — С. 220-223. — Бібліогр.: 9 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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AT kravchenkooyu influenceofdustparticlesonrfdischargeplasmaafterglow AT maruschakis influenceofdustparticlesonrfdischargeplasmaafterglow AT yushchyshenayuv influenceofdustparticlesonrfdischargeplasmaafterglow |
| first_indexed |
2025-07-06T08:45:19Z |
| last_indexed |
2025-07-06T08:45:19Z |
| _version_ |
1836886550213820416 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2015. №1(95)
220 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2015, № 1. Series: Plasma Physics (21), p.220-223.
INFLUENCE OF DUST PARTICLES ON RF-DISCHARGE PLASMA
AFTERGLOW
O.Yu. Kravchenko, I.S. Maruschak, Yu.V. Yushchyshena
Taras Shevchenko Kyiv University, Kyiv, Ukraine
E-mail: kay@univ.kiev.ua
In this paper we report about results of computer simulation by PIC/MCC method of the discharging of dust
particles in the plasma afterglow and time dependence of plasma parameters in discharge gap after switching off the
voltage. It is shown that discharging of dust particles in the afterglow plasma after switching off voltage of
radiofrequency discharge occurs faster in the central part of the electrode gap due to the ion cloud forming and
intense recombination of electrons in collisions with dust particles in this area. Moreover, the discharging rate is
increasing with increasing of the dust particles density. In the initial stage after the switching off the voltage plasma
has a positive potential relative to the electrodes. Eventually, when the electron and ion densities are significantly
reduced, the charge of the plasma is determined by the amount of negative dust particles. In this case, the plasma
potential is negative relative to the electrodes, which contributes to the effective diffusion of dust particles on the
walls of the discharge chamber.
PACS: 52.27.Lw.
INTRODUCTION
Dusty or complex plasmas are partially ionized gas
composed of neutral species, ions, electrons, and
charged dust particles. Radio-frequency discharge is
often used to create dusty plasma. Dust particles are
charged in plasma and can significantly affect the
plasma parameters. Dust-particle charge is a key
parameter in complex plasma. It determines the
interaction between a dust particle and electrons, ion, its
neighbouring dust particles, and electric field.
Knowledge of dust charge will allow us to understand
the basic properties of dusty plasma, particle dynamics
in dust clouds, and methods to manipulate the particles.
Thus one of the main dusty plasma challenges is to
understand the dust charging in a wide range of
experimental conditions, which simulates industrial and
space plasmas.
There are many publications reporting on the
investigation of dust charging in discharge plasma.
However there are only a few papers devoted to dust
charging, or discharging to be more specific, in the
discharge afterglow. These papers report that dust
particles retained residual electric charges when the
power of the discharge was switched off. Nevertheless,
the discharging phenomenon was not totally understood.
In [1], the nanoparticles’ spatial distribution in a dusty
plasma afterglow was studied and it was found that
most of the dust particles were neutral. The variation of
charge of dust particles in the afterglow of a complex rf
plasma in microgravity conditions was investigated
experimentally and theoretically in [2-4], and the
existence of negative residual charges on the dust
particles was shown.
Properties of plasma afterglows with large dust
density were studied in [5, 6]. In the afterglow
experiments, the electron density showed an unexpected
increase at the very beginning of the plasma decay.
In this paper, we study the time dependencies for the
plasma parameters and the dust charge in the afterglow
of a radio-frequency discharge with dust particles, using
PIC/MCC simulation.
MODEL AND SIMULATION METHOD
A one-dimensional RF discharge is considered
between two plane electrodes separated by a gap of
0.08d m which is filled with Ar at pressure
p=0.1 Torr. At initial time dust particles of a given
radius 100dr m are distributed uniformly in the
region x d and there are no dust particles near
electrodes x and d x d ( 0.001 )m . The
dust particles collect and scatter electrons and ions
distributed in the discharge with density
en and
in ,
respectively.
The PIC/MCC method was described in detail in [7]
for discharges without dust particles. It was developed
for computer simulations of the RF discharge with dust
particles [8]. The Monte Carlo technique is used to
describe electrons and ions collisions. The collision
types include elastic collisions of electrons and ions
with atoms, an ionization and excitation of atoms by
electrons, the 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 [9].
The model took into account the secondary electron
emission from the surface of the dust particles in
collisions of ions with dust particles. Simulations have
been carried out at several different dust densities
(nd=0…5∙10
13
m
-3
) and secondary emission yields
( i=0…0.8). A harmonic external voltage
0( ) sin(2 )eV t V ft at a frequency 10f Mhz MHz and
amplitude
0 150V V sustains the RF discharge.
Simulation of radio-frequency discharge lasted for 100
periods. During this time, a quasi-steady mode of
discharge is established, when the average for the period
parameters of plasma do not change. After that, the
voltage between the electrodes is switched off and the
plasma begins to decay. According to our model, the
plasma particles can disappear due to recombination on
the walls and dust particles.
ISSN 1562-6016. ВАНТ. 2015. №1(95) 223
RESULTS AND DISCUSSION
Simulations of a plasma afterglow after switching
off radio-frequency discharge were carried out at
different values of the dust particles density and yields
of secondary electron emission from the surface of the
dust particles.
Fig. 1 shows the charge density of dust particles at
different times after switching off the voltage. Curves in
Fig. 1, a correspond to the case
13 310dn m and
curves in Fig. 1, b correspond to the case
13 35 10dn m . In both cases, it was assumed that the
secondary emission coefficient is 0.4i
. As can be
seen from the figure, the charge of dust particles is
decreased with time in magnitude in the central part of
the inter-electrode gap. Moreover, discharging of dust
particles is faster in case of dust density increasing. To
understand the cause of this phenomenon, we analyze
the temporal variation in densities of electrons and ions
in the plasma afterglow both with and without dust
particles.
0,00 0,02 0,04 0,06 0,08
-1,0x10
-4
-5,0x10
-5
0,0
d
, C/m
3
t,s
t=5*10
-5
s
t=1.2*10
-4
s
a
0,00 0,02 0,04 0,06 0,08
-2,0x10
-4
-1,5x10
-4
-1,0x10
-4
-5,0x10
-5
0,0
d
, C/m
3
t,s
t=5*10
-5
s
t=1.2*10
-4
s
b
Fig. 1. Spatial distributions of charge density of dust
particles ( a 13 3100 , 10d dr nm n m ;
b 13 3100 , 5 10d dr nm n m )
In Fig. 2 are represented spatial distributions of
electron density (a) and ion density (b) for case without
dust particles in the discharge ( 0dn ). In this
calculation, the voltage was turned off at time
55 10t s . Dependences above show that sheaths
arise near the electrodes and peaks of ion and electron
densities are formed at their boundaries. It is seen from
Fig. 2 that electron and ion densities are changing
slightly at the next time interval 52 10t s .
Distributions of electrons and ions in plasma afterglow
with dust particles are shown in Fig. 3. In the central
part of the inter-electrode gap the ion and electron
densities are being reduced over time, however electron
density is being decreased faster.
0,00 0,02 0,04 0,06 0,08
0,0
4,0x10
14
8,0x10
14
n
e
,m
-3
x, m
t=5 10
-5
c
t=6 10
-5
c
t=7 10
-5
c
a
0,00 0,02 0,04 0,06 0,08
0,0
4,0x10
14
8,0x10
14
n
i
, m
-3
x, m
t=5 10
-5
c
t=6 10
-5
c
t=7 10
-5
c
Fig. 2. Spatial distributions of electron (a) and ion (b)
densities at different times after the switching off rf-
discharge without dust particles
0,00 0,02 0,04 0,06 0,08
0
1x10
15
2x10
15
n
e
, m
-3
х, м
t=5 10
-5
c
t=5,1 10
-5
c
t=5,3 10
-5
c
a
a
0,00 0,02 0,04 0,06 0,08
0
1x10
15
2x10
15
n
i
, m
-3
x, m
t=5 10
-5
c
t=6 10
-5
c
t= 10
-4
c
Fig. 3. Spatial distributions of electron (a) and ion (b)
densities at different times after the switching off rf-
discharge for 13 3100 , 5 10d dr nm n m
Thus, at time 57 10t s electrons in the central part
of the inter-electrode gap is practically absent. At these
times only ion current flows on dust particles, which
leads to decreasing of dust particle charge in magnitude.
On the contrary, electron clouds are formed in the
sheaths, which are stored for a long time. This leads to
b
b
222 ISSN 1562-6016. ВАНТ. 2015. №1(95)
that the electron current on the dust particles is
considerably long time and as a result, the charge of the
dust particles near the electrode is changed slowly.
0,00 0,02 0,04 0,06 0,08
0
10
20
30
V
x, m
t=5*10
-5
s
t=6*10
-5
s
t=7*10
-5
s
a
0,00 0,02 0,04 0,06 0,08
-150
-100
-50
0
50
,V
x, m
t=5e-5s
t=5.1e-5s
t=5.3e-5s
b
Fig. 4. Averaged over the period of rf-discharge spatial
distributions of electric potential in the plasma
afterglow for the case 0dn (a) and
13 310 , 100d dn m r nm (b)
Fig. 4 shows spatial distributions of electric potential
at different times, indicated in the figure, for the cases
0dn (a) and 13 310dn m (b). In the case of
absence of dust particles in the discharge, region of
constant positive potential with respect to the electrodes
is observed in the central part of the inter-electrode gap.
Near the electrodes are formed sheaths in which there is
an abrupt change of the potential. Over time after
switching-off the voltage, the value of potential jumps
in the sheaths, as well as the positive potential in the
center of the electrode gap are decreased.
With the presence of dust particles in the discharge
chamber other potential distribution are observed.
Immediately after switching off the voltage the potential
plasma is positive toward the electrodes. Near the
electrodes are formed potential jumps (about 60 V), and
its maxima at the sheaths edges. This is due to the fact
that the charge of the plasma in the inter-electrode gap
is positive. Over time, the plasma potential is decreasing
due to decreasing of the ion density. As a result, at the
time 410t s the charge of the plasma is negative,
since the negative charge of the dust particles exceeds
the charge of the ions. This causes a negative plasma
potential relative to the electrodes.
Fig. 5 shows phase portraits of ions for the case
13 310 , 100d dn m r nm at different times. It is seen
that ions are accelerated towards electrodes in sheaths
when the discharge is supported by the applied voltage
(see Fig. 5,a). At the stage afterglow plasma ions reflect
from the walls and oscillate in the central region of the
discharge chamber (see Fig. 5,b). In this case, the ion
velocity distribution function is broadened significantly,
indicating an increase in their average thermal energy.
0,00 0,02 0,04 0,06 0,08
-1,5x10
4
-1,0x10
4
-5,0x10
3
0,0
5,0x10
3
1,0x10
4
t=5e-6 s
V
xi
, m/s
x, m
a
0,00 0,02 0,04 0,06 0,08
-1,5x10
4
-1,0x10
4
-5,0x10
3
0,0
5,0x10
3
1,0x10
4
t=7e-6 s
V
xi
, m/s
x, m
b
Fig. 5. The phase portrait of ions for the case
13 310 , 100d dn m r nm at time
55 10t s (a) and
57 10t s (b)
CONCLUSIONS
Discharging of dust particles in the plasma afterglow
after switching off the voltage of radio-frequency
discharge occurs faster in the central part of the
electrode gap. Moreover, the discharge rate increases
with increasing of the dust particles density. Since
negatively charged dust particles are remained in the
volume, the plasma potential is negative relative to the
electrodes. Remaining in the discharge ions are trapped
in the potential well, and for negatively charged dust
particles there are conditions for the diffusion to the
walls.
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Article received 12.12.2014
ВЛИЯНИЕ ПЫЛЕВЫХ ЧАСТИЦ НА ПОСЛЕСВЕЧЕНИЕ РАДИОЧАСТОТНОГО РАЗРЯДА
О.Ю. Кравченко, И.С. Марущак, Ю.В. Ющишена
Представлены результаты компьютерного моделирования методом PIC/MCC разрядки пылевых частиц в
послесвечении плазмы радиочастотного разряда и временные зависимости параметров плазмы в разрядном
промежутке после выключения напряжения. Показано, что разрядка пылевых частиц в послесвечении
плазмы после выключения напряжения радиочастотного разряда происходит быстрее в центральной части
межэлектродного промежутка, что обусловлено образованием ионного сгустка и интенсивной
рекомбинацией электронов при столкновении с пылинками в этой области. Кроме того, скорость разрядки
увеличивается с увеличением плотности частиц пыли. В начальной стадии после выключения напряжения
плазма имеет положительный потенциал относительно электродов. В конце концов, когда концентрации
электронов и ионов значительно снижаются, заряд плазмы определяется количеством отрицательных частиц
пыли. В этом случае потенциал плазмы является отрицательным по отношению к электродам.
ВПЛИВ ПИЛОВИХ ЧАСТИНОК НА ПІСЛЯСВІТІННЯ РАДІОЧАСТОТНОГО РОЗРЯДУ
О.Ю. Кравченко, І.С. Марущак, Ю.В. Ющишена
Представлено результати комп'ютерного моделювання методом PIC/MCC розрядки пилових частинок у
післясвітінні плазми радіочастотного розряду та часові розподіли параметрів плазми в розрядному проміжку
після вимкнення напруги. Показано, що розрядка пилових частинок у післясвітінні плазми після вимкнення
напруги радіочастотного розряду відбувається швидше в центральній частині міжелектродного проміжку,
що пов’язано з утворенням іонного згустка та інтенсивною рекомбінацією електронів при зіткненні з
пилинками в цій області. Крім того, швидкість розрядки збільшується зі збільшенням концентрації частинок
пилу в розряді. На початковій стадії після вимкнення напруги плазма має позитивний потенціал щодо
електродів. Зрештою, коли концентрації електронів та іонів значно знижуються, заряд плазми визначається
кількістю негативних частинок пилу. У цьому випадку потенціал плазми є негативним по відношенню до
електродів.
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