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21 International Symposium on Plasma Chemistry (ISPC 21)
Sunday 4 August – Friday 9 August 2013
Cairns Convention Centre, Queensland, Australia
The study of pulse bias collaborative RF plasma in the surface modification of
PET film
Ying Guo, Yuncheng Shi, Shijian Shi, Jing Zhang
1
College of Science, Donghua University, Shanghai 201620, P. R. China
Abstract: A systematic study of pulse bias collaborative the RF (ICP) plasma surface modification of PET film and its surface physical and chemical changes were analyzed. It was
found that with a pulse bias collaborative the RF plasma, the contact angle was reduced to
17 ° in 5 seconds and RMS roughness is enhanced by 7 times higher than that of only plasma
treatment film. The Atomic force microscopy (AFM) and X-ray photo electron spectroscopy
(XPS) were employed to investigate the surface characteristics with the collaborative plasma
treatments. The amount of oxygen-containing polar functional groups was also elevated with
the plasma treatment. Both the enhancements of surface roughness and oxygen-containing
functional groups explain the improvements of hydrophilicity and cohesiveness achieved on
PET film by the collaborative plasma.
Keywords: Pulse bias voltage, PET film, RF plasma, Surface modification
1. Introduction
Technologies for flexible electronics have been developed to make electronic or micro-electromechanical devices on flexible organic substrates. However, the metal-polymer adhesion is generally poor since the cohesive
energy of metals is two orders of magnitude higher than
that of polymers [1-2]. There are different methods to
modify the surface properties of the polymer films such as
chemical etching, corona discharge, plasma treatment,
and bombardment with charged particles [3-5].
Recently, a large number of studies indicate that the
plasma treated polymer (PET/PI) surface to improve the
surface roughness and the hydrophilic effect is obvious
[6-9], in addition to the role of the plasma can also change
the PET film and the metal film adhesion [5], but overall,
the plasma processing of materials longer time (> 35s) [9],
which hinders the further application of plasma surface
technology. Therefore, this article by introducing direct
current (DC) pulse bias collaborative the RF discharge
technology in the fast surface modification effect.
2. Experimental
The pulse bias collaborative the RF plasma system is
depicted in Fig.1. The glass transition temperature of PET
is 80°C, a radio frequency (RF) Continuous discharge
conditions, the chamber temperature is higher, PET material very easily deformed, so the use of radio-frequency
pulse discharge mode, to ensure that materials processing
effect, but also to prevent deformation of the material. Basic conditions for the discharge gas pressure 1.9Pa,
RF power modulation frequency 200Hz, 50% duty cycle,
the discharge power 100W, DC bias modulation frequen-
cy 200Hz, 50% duty cycle, the processing time is 15S, the
chamber of oxygen and argon, ratio of 1:12.
U.S. Veeco NanoScope IV produced by atomic force
microscopy (AFM); XPS is manufactured from Perkin
Elmer PHI 500C type, X-ray source target Mg Kα line, a
45° angle with the sample test and analysis; adhesive
mechanical properties of the test, the JapaneseBird Tianjin produced AGS-500ND type universal material testing
machine; JC2000A type contact angle measurements,
using the amount of contact angle measurement Supreme
Court, measuring five different positions for each sample,
the mean value.
Fig.1 Schematic diagram of bias RF discharge
3. Results and discussions
The surface topography of plasma treated PET film was
investigated by AFM. Fig.2 shows the AFM images of the
PET film. As seen in Fig. 2a, the surface of untreated PET
film surface was relatively smooth with conical protuberances and moderate roughness. After only plasma treatment (Fig. 2b), the number of the conical protuberances
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21 International Symposium on Plasma Chemistry (ISPC 21)
Sunday 4 August – Friday 9 August 2013
Cairns Convention Centre, Queensland, Australia
has increased. When the DC bias voltage is-800V (Fig.
2c), the surface of the cylindrical projection thicker, PET
film surface is significantly etched.
ential etching between amorphous and crystalline regions
of the polymer [10].
Fig.3 Contact angle and RMS roughness values as a function of
bias
In order to investigate the effect of bias collaborative
plasma treatments on the surface chemical modifications,
chemical bonding states on the treated PET surfaces were
measured by XPS.
Tab.1 the surface contents of the untreated and treated
PET film
Sample
Binding energy (eV)
Binding states
Fig.2 AFM images of the PET film (a) Untreated, (b)only plasma, (c) bias (-800v)
PET film surface roughness and the contact angle is a
function of bias voltage (Fig. 3). Contact angle significantly reduced the role of bias, when the bias is -800V,
the minimum contact angle can be reduced to 17°in 5
seconds and the RMS roughness is enhanced by 7 times
higher than that of only plasma treatment film.
It is seen that the values of RMS gradually increase
with increasing oxygen content. Surface roughening of
polymer substrate were proposed to be caused by differ-
Component ratio
284.7
C-C
286.1
288.7
O-CH2
O-C=O
Untreated
67.27
19.77
12.96
bias0V
56.65
22.19
13.54
bias-400V
51.52
23.55
6.28
bias-800V
45.52
34.55
16.79
Binding energy (eV)
291.0
531.9
533.3
Binding states
π－π
O*=C-
O*-C=O
Untreated
—
49.94
50.06
bias0V
7.62
66.08
33.92
bias-400V
18.65
78.77
21.23
bias-800V
3.14
82.45
17.55
The carbonyl oxygen (O * = C) bond content increased,
aliphatic oxygen O *-C = O decreased, which may be
oxygen-containing functional groups of adhesion has been
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21 International Symposium on Plasma Chemistry (ISPC 21)
Sunday 4 August – Friday 9 August 2013
Cairns Convention Centre, Queensland, Australia
released, resulting in decreased oxygen aliphatic group.
This shows that the plasma bombardment open benzene
CC bond, and with the oxygen in the reaction chamber to
form O*= C- containing functional groups such as [11].
And the methyl carbon (O-CH2) content increased, the
PET surface hydroxyl content increases, the sputtering
plating process, can produce Au-O bond, and the gold
film to increase the binding force between the PET film
[12], suggesting that polar oxygenated functional groups
to improve the bonding of PET film plays an important
role.
A wire-type Langmuir probe located from the target is
used to determine plasma parameters and sheath evolution
is estim ated by depletion of electron saturation current.
The electron saturation current is measured with the probe
biased at +20V higher than the plasma potential of 16 V.
Fig.4 Time evolution of (a) target bias voltage and (b) probe
current for the ICP discharge power of 200 W.
The time evolution of the target voltage as well as the
probe current is shown in Fig. 4. The pulse voltage is applied after 20μs from the end of the pulse modulated discharge. The probe current increased a proximately by a
factor of ~2 during the application of the negative high
voltage (HV) pulse bias of -3.5 kV in amplitude, and was
gradually recovered after the end of the HV pulse.
Similarly ICP discharge conditions, the bias collaborative plasma emission spectroscopy diagnosis, and 750nm
of Ar plasma characteristic lines through comparative
methods to estimate intensity analysis, the results shown
in Fig. 7. It shows that plasma reactive species have relation to the collaborative period.
This may explain the bias collaborative plasma surface
treatment of the polymer film play a significant role in the
cause.
Fig.5 under different spectral intensity pulsed bias test results
(pulse width 85μs)
4. Summary
In this thesis, a DC bias pulse collaborative ICP plasma
discharge device, RF13.56MHz, pulse modulation frequency 200Hz, 50% duty cycle, pulsed DC bias studied
synergies of PET film surface treatment effect . The following conclusions:
(1) pulsed bias with increases in the 5S PET film to
rapidly reduce the contact angle to 17°, and RMS roughness is enhanced by 7 times higher than that of only
plasma treatment film.
(2) Test by AFM and XPS analysis, the bias collaborative plasma treatment, PET film surface etching phenomenon obviously, roughness increases, the methyl carbon
(O-CH2) content increased, the PET surface hydroxyl
content increased. Polar oxygenated functional group to
improve the bonding of PET film plays an important role.
Through the above conclusions Description DC pulsed
bias can quickly and effectively improve the PET film
surface roughness and the number of oxygen-containing
functional groups, thereby increasing hydrophilicity and
surface adhesion, in order to further improve the plasma
surface modification process was provided.
5. References
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21 International Symposium on Plasma Chemistry (ISPC 21)
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Cairns Convention Centre, Queensland, Australia
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6. Acknowledgement
This work was funded by the Natural Science Foundation of China (Grant No. 11005017, and 10835004)