Spatial and Temporal Analysis of Microplasma Light Emission
for the Surface Treatment Processes
Marius Blajan, Hodaka Fukunaga and Kazuo Shimizu
Organization for Innovation and Social Collaboration, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, JAPAN; E-mail：blajanmarius@yahoo.com

Introduction
Microplasma
canbefoundinmany
applications. Technology was used in for NOx
removal, surface treatment and sterilization or
inactivation of bacteria.

A high intensity electric field (107-108 V/m)assures the formation of microplasma and acorresponding discharge current.

Negative
electrode Negative glow(high voltage)

wastreatedDiameterØ~10 µm

Discharge current

GND

1A25 ns150 ns60 µmby0 ns

Grounded Positive Faraday dark
spaceelectrode column

Experimental Setup

60 ns 90 ns 120 ns 150 ns100 µm

C(1)Microplasma Electrodes

30 ns

A

Fig. 5 Phenomena of microdischarges.

The electrodes consist in perforated metallic
plates covered with a dielectric layer.

Emission Spectroscopy
Emission spectrum was measured
camera shutter opened for 1 µs.

with

18000

0.5-0.55
0.75-0.8(a)

16000
14000

Intensity (a.u.)

Fig. 8 Temporal evolution of microplasma discharge.
Gating of ICCD camera was set at 3 ns.

Ar I

Ar I

0.55-0.6
0.8-0.85

Cathode12000
10000

Ar I

8000
6000

0.6-0.65
0.85-0.9

0.65-0.7
0.9-0.95

Anode160

Ar I

Ar I

100

4000
2000

Fig. 1 Microplasma electrodes

60

0410

415

420

425

430

435

440

40

Wavelength (nm)18000
214000(2) Experimental setup

20
N2 SPS

10000

108000N2 SPS

6000

N2 SPS

OH02000
0280 300 320 340 360 380 400 420 440 460 480 500
Wavelength (nm)

16000
14000

Intensity (a.u.)

30

12000

4000

Emission spectrum was measured by aspectrometer, an ICCD camera and aphotomultiplier
tube.
Photosofmicrodischarges
weretakenusinga
microscope and a digital camera.
Gas flow rate: Ar, N2/Ar and O2/Ar at 10L/min.

Ar
0.5% N2 in Ar(b) N SPS
2N SPS

16000
Intensity (a.u.)Electrode size was 20 mm versus 40 mm foremission spectroscopy analysis. Discharge gap
was set from 30 μm to 100 μm in this study.
A Marx Generator with MOSFET switches aspulse power supply:•Output Voltage: -2 kV negative•Rise time: 100 ns•Pulse width: 1 µs

0.7-0.75
0.95-1Time (ns)surface

GND

500 V
25 ns

Discharge voltage

Thedevelopment
andoptimizationofmicroplasma technologies depend on theclarification of microplasma physics. Our
microplasma is a dielectric barrier discharge
at atmospheric pressure.
L-lacticacid
microplasma.

1% N2 in Ar at 1 kV

0.5% O2 in Ar
1% O2 in ArAr(c)4080

120 160 200 240 280

0Distance X (um)Fig. 9 Spatial and temporal evolution of relative
intensity of N2 SPS peak at 337.1 nm for
microplasma in 1% N2 in Ar. Gating of ICCD camera
was set at 3 ns.

4000

Spatial and temporal distribution for the N2
SPS peak at 337.1 nm inside the discharge
gap shown a maximum intensity towards theanode for the 25 ns corresponding to the risetime of discharge current and it shifted after
towards cathode.

2000

Surface Treatment of L-lactic acid

12000
10000
8000
6000

0300 302 304 306 308 310 312 314 316 318 320
Wavelength (nm)Fig. 6 Emission spectrum of microplasma in: (a) Ar;(b) N2/Ar; (c) O2/Ar at -1.2 kV.
Fig. 2 Experimental setup for emission spectroscopy.

LeftelectrodeactiveMeasuredarea

Gas flow(a)LeftelectrodeactiveMeasuredarea

Gas flow(b)

Fig. 3 Measured area of emission spectra: (a)outside the electrode; (b) in discharge gap.

N2 molecules excited argon neutrals andreaction in argon plasma with N2 addition:
Ar*+ N2(X1Σg+)v=0 → N2(C3πu)v’=0 + Ar
Spontaneous radiation of formed excitedstate of nitrogen:N2(C3πu)v’=0 → N2(B3πg)v’’=0 + hνSpatial distribution outside of electrodes
shows a distribution of about 1 mm for theOH peak at 309 nm and 500 µm for the Ar I
peak at 696.54 nm respectively.

(3) Polymer film treatment
wasOH peak 309 nm

1Ar I peak 696.54 nm
0.8Fig. 10 AFM analysis of the polymer surface before(left side) and after (right side) microplasma
treatment with Ar.

0.4

Grounded electrode

00200

400

•Streamer diameter was proportionally withthe discharge gap.
•Spatial distribution of ArI peak at 696.54nm and OH peak at 309 nm outside thegrounded electrode was measured up to 500µm for ArI peak and 1 mm for OH peak
respectively.

0.60.2

600

800

1000

Distance (um)Fig. 7 Spatial distribution of OH radical and Ar I
at the outside of grounded electrode forelectrode arrangement shown in Fig. 3 (a).
Fig. 4 Experimental setup for surface treatment ofpolymer film.

TreatedConclusions

1.2

Relative intensity (a.u.)

L-lactic acid (C3H6O3) polymer film
treated by remote microplasma process.

Untreated

The streamer diameter was proportionallywith the discharge gap and thinner thanpreviously reported.

•Light near the cathode was preceded by thewaves of light intensity that started directlyfrom the anode and propagated towards thecathode.
•Polymer’s
surfacehydrophilicity
wasimproved by microplasma treatment. AFM
analysis showed modifications at the surfaceof polymer.