22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Innovative atmospheric pressure plasma jet for copper particles synthesis
A. Lazea-Stoyanova1, V.S. Teodorescu2 and G. Dinescu1
1
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, 77125 Magurele, Bucharest,
Romania
2
National Institute of Materials Physics, 105bis Atomistilor Street, 77125 Magurele, Bucharest, Romania
Abstract: Copper particles were obtained using an atmospheric pressure radiofrequency
argon plasma jet method. The plasma jets as well as the micro and nano-metric metallic
particles have been carefully investigated. Hence, various analyzing techniques were
employed, such as Optical Emission Spectroscopy, optical microscopy, Scanning Electron
Microscopy and Energy-dispersive X-ray spectroscopy.
Keywords: copper particles synthesis, low-temperature plasma jet, atmospheric pressure
1. Introduction
Over the time, various methods for metallic particles
synthesis were developed due to their wide usage in many
sectors of industry and technology. Hence, metallic
powders can be prepared by metallurgical reduction,
fuming, atomization, electrolysis, grinding, precipitation,
spray drying and plasma-based techniques [1].
For this study a plasma technique was used due to its
advantages when compared with other synthesis methods,
such as better process control and a large variety of
particles types. Within the plasma synthesis category two
approaches can be distinguished: decomposition of
metallic precursors (chemical processes) or ablation,
sputtering, evaporation of pure metals followed by vapour
condensation (physical processes) [2]. In order to obtain
evaporation/condensation processes, high-temperature as
well as low-temperature plasmas are nowadays used in
particle synthesis.
Our approach refers to the
development and testing of a radiofrequency plasma jet,
working under atmospheric pressure, suitable for copper
particle synthesis. In this manner we aim to combine the
advantages of atmospheric pressure process with the ones
derived from non-thermal plasmas.
2. Experimental details
The schematic drawing of the set-up is presented by
Fig. 1. The detailed working principle is described
elsewhere [3, 4]. To quickly explain the working
principle it must be mentioned that the powered electrode,
connected to a 13.56 MHz generator, is made out of
copper and has a hollow design [4] allowing the gas
admission in the discharge. The grounded electrode is
made out of stainless steel and has a 1 mm nozzle through
which the plasma expands from the discharge chamber
into the processing chamber. In the processing room Si
substrates are placed and, thus, the particles are collected.
The working gas was argon (1000 sccm and 5N purity).
Other parameters were: 27 mm the distance between the
electrodes, 6 mm the distance between nozzle and
substrate, 1 h exposure time, 100 W power, 1040 mbar
operating pressure and 10-5 mbar base pressure.
P-II-7-5
Gas inlet
(Ar)
Quartz
window
O
ES
Plas
ma
Pumping
/
Outflow
Substr
ate
Fig. 1. Experimental set-up of the atmospheric
plasma jet used for particles preparation.
To analyse the plasma OES was used.
The
measurements were performed using a optical quartz fibre
(200 µm diameter) and a Horiba Jobin Yvon imaging
spectrograph (0.1 nm resolution) equipped with ANDOR
IDus CCD camera and an integration time of 2 s. The
particles were characterized by a scanning electron
microscope (SEM) FEI Inspect S50 apparatus, using
20 kV acceleration voltage and by energy-dispersive
X-ray spectroscopy (EDS) data were acquired in a
transmission electron microscope (JEOL ARM 200F).
3. Results and discussions
After 1 h plasma exposure, onto the Si substrate a 6 mm
reddish brown spot was observed (Fig. 2a). The OES
spectrum of the plasma jet presented in Fig. 2b was
recorded at the middle distance between the substrate and
the nozzle. The spectra shows Ar signature (between 700
and 900 nm), Cu I atomic lines at 324.6, 327.3 and
489.4 nm. Moreover, the OH-radical emission band
(centred at 308 nm) is noticed. The Ar lines are due to the
1
argon discharge gas and the Cu lines prove that plasma is
containing copper material that could only be provided by
the powered electrode. The presence of OH radical is
explained by the ambient atmosphere or impurities
contained within the discharge gas.
10
a)
Cu
8000
a)
Counts
6000
7000
4000
6000
Intensity (a.u.)
OH
5000
2000
Cu
Ar
4000
0
0
3000
b)
2000
0
300
400
500
600
700
800
900
10
15
20
Energy (keV)
1000
Wavelenght (nm)
Fig. 2. a) Image of plasma deposited spot onto
the Si substrate, presenting a reddish brown spot
compared with a 1 cent euro coin (copper
covered-steel coin with a diameter of 16.25 mm);
b) OES graph of the atmospheric pressure plasma
jet.
Fig. 3a shows the SEM image of the particles. One can
notice micro-metric particles (~ 2 µm in diameter) that do
not tend to agglomerate. In addition, particles of about
100 nm are obtained, described in [4].
The EDS spectrum presented in Fig. 3b points out to the
fact that Cu signatures are dominating the spectra (some
traces of Si are seen due to the substrate). Hence, the
obtained particles are made out of copper.
This information, correlated with the OES findings,
sustains the hypothesis that copper material is removed
from the powered electrode, most probable by
evaporation, and the copper atoms coagulate into
particles. Moreover, the fact that the particles are not
agglomerated and can be easily removed from the
substrate indicates that the particles are formed before
reaching the substrate.
2
5
Fig. 3. a) SEM image of the obtained particles;
b) EDX spectrum taken in the same area as the
SEM image, however for higher magnification.
1000
b)
Cu
Si
4. Conclusions
A radiofrequency plasma jet was used successfully used
to produce metallic particles at atmospheric pressure. It
was shown that copper particles can be produced directly
from copper bulk material coming from the powered
electrode. They have micro-metric and nano-metric sizes,
do not tend to agglomerate and are not strongly attached
on substrate.
5. Acknowledgements
The authors acknowledge the financial support
provided by a research contract in the frame of RomaniaFrance IFA-CEA collaboration, project DUSTCO code
C4-13.
6. References
[1] R.M. Young and E. Pfender. Plasma Chem. Plasma
Process., 5, 1 (1985)
[2] I. Pilch, D. Soderstrom, M.I. Hasan, U. Helmersson
and N. Brenning. Appl. Phys. Lett., 103, 193108
(2013)
[3] A. Lazea-Stoyanova, M. Enculescu, S. Vizireanu,
V. Marascu and G. Dinescu. Digest J. Nanomat.
Biostruct., 9, 1241 (2014)
[4] A. Lazea-Stoyanova, A. Vlad, A.M. Vlaicu,
V.S. Teodorescu and G. Dinescu. Plasma Process.
Polymers, in press; DOI: 10.1002/ppap.201400197
(2015)
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