Emission spectroscopy of microplasma
for the surface treatment of glass
Marius Blajan, Akira Umeda and Kazuo Shimizu
Innovation and Joint Research Center, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, JAPAN; E-mail：blajanmarius@yahoo.com

Introduction

The aim of this research is to analyze
microplasma by emission spectroscopy for theprocess of glass surface treatment. Otherresearch groups investigated nonthermal
plasma for surface treatment with similar
characteristics such as high electron, and low
rotational temperatures which recommends
that this technology could be applied for thesurface modification due to its low gas
temperature and molecular excitation ability.
Our microplasma has this characteristics
obtained at relatively low discharge voltages
around 1 kV which can be advantageous infurthermore implementing the technology inindustry.

Experimental Setup(1)Microplasma Electrodes
The electrodes consist in perforated metallic
plates covered with a dielectric layer.

(a)

(b)

Waveform of the discharge voltage, discharge
current and emission signal of microplasma
discharge (337.1 nm) in 1% N2 in Ar and in N2.

Experimental setup: (a) emission spectroscopy;(b) surface treatment.

(4) Electrical Characteristics
Very small discharge gaps and relatively low
discharge voltages (about 1 kV)⇨A high intensity electric field (107-108 V/m)assures the formation of microplasma and acorresponding discharge current.

(a)

(b)

Surface Treatment of Glass

Waveforms of the discharge voltage, corresponding
discharge current and gate signal for ICCD camera:(a) Marx Generator; (b) Neon transformer.

Microplasma electrodes
Emission spectrum was measured
camera shutter opened for 1 µs.

Marx Generator with MOSFET switches:•Output Voltage: -2 kV negative•Rise time: 100 ns•Pulse width: 1 µs
•Frequency: 1-24 kHz
Neon transformer•Output voltage: up to 2 kV AC•Frequency 24 kHz

(a)

14000

Intensity (a.u.)(2) Power Supplies

with18000
16000

Ar I

0.5% N2 in Ar at 1.3 kV3530252015100Ar I

12000
10000

05Ar IAr I

101520253035Treatment time (sec.)

Contact angle of a water droplet at the surface ofglass versus treatment time by microplasma
discharge in 0.5 % N2 in Ar.

Ar I6000455Ar I

8000

A neon transformer was used to energize theelectrodes at 1.3 kV. With the increase oftreatment
timethecontact
angle
isdecreasing from 41.5°without treatment to8.5°after 30 seconds.
40Emission Spectroscopy
Electrode size was 20 mm versus 40 mm foremission spectroscopy analysis. Discharge gap
was set at 50 μm in this study.
Microplasma electrodes for surface treatment
have 40 mm diameter .

Lifetime emission signal of N2 SPS peak at
337.1 nm increased from 40 ns to 260 ns
when 1% N2 was added in Ar.
VibrationalquantumnumberdifferenceΔv=v’-v”=-2 was chosen to determine thevibrational temperature of N2(C). The valueof vibrational temperature was Tvib=3160 K.
Electron temperature was calculated using
line to continuum ratio of ArI peak at 430
nm: Te = 23000 K.
LIFBASEsoftwarewasusedfor
thecalculation of the rotational temperature.
Tgas = Trot = 300 K⇨Microplasma=Nonthermal plasma

Contact angle (deg.)

Microplasma
canbefoundin
manyapplications. In the last years, the technology
was used in applications such as NOx removal,
surfacetreatmentandsterilization
orinactivationofbacteria.
Emission
spectroscopy is one of the methods to analyze
plasma process . The emission spectrum willallow
thecalculationofmicroplasma’s
electron,vibrational
androtationaltemperatures which due to the particularities
of microplasma such as small discharge gap,
can be measured only by these non invasivetechnique.

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 + hν

4000
2000
0Before treatment
414 416 418 420 422 424 426 428 430 432 434

After treatment

Wavelength (nm)
18000
16000
14000
Intensity (a.u.)+VTrigger

Ar
0.5% N2 in Ar(b) N SPS
2N SPS
212000N2 SPS

10000
8000
6000
4000

N2 SPSOH

N2 SPS

2000

Vout

0280 300 320 340 360 380 400 420 440 460 480 500
Wavelength (nm)Emission spectrum of microplasma in: (a) Ar;(b) N2/Ar at -1.2 kV.

Photo of negative pulse Marx Generator.

(3) Experimental setup
Emission spectrum wasspectrometer, an ICCD
photomultiplier tube.

measured bycamera andaaA microplasma enclosed reactor was used forsurface treatment of glass. A contact angle
meter was used to measure the contact angleof a water droplet at the surface of glass.
Gas flow rate: Ar and N2/Ar at 10 L/min.

Contact angle of a water droplet at the surface ofglass before and after microplasma treatment..

Emission spectrum in Ar and Ar/N2 shows:•N2 second positive band system peaks at315.9, 337.1, 357.7, 380.4, 400 and 405 nm.
•N2+ first negative band system peak at391.4 nm.
•OH peaks at 306.4, 307.8 and 308.9 nm.
•Ar I peaks were measured at 415.8, 419.1,419.8, 420.1, 426.6, 427.2, 425.9, 433.3,696.5, 706.7, 727.3, 738.3; 703.2, 750.4 and772.4 nm.

Conclusions•Emission spectrum of microplasma shown
intensity peaks of N2 SPS and N2+ FNS, OHand ArI.
•Lifetime emission signal peak of the 337.1
nm N2 SPS peak for microplasma in N2 was40 ns and 260 ns when 1% N2 was added inAr.
•Temperatures of microplasma: Trot = 300 K;
Tvib = 3160 K; Te = 23000 K  thistechnology could be applied for the surface
modification due to its low gas temperatureand molecular excitation ability obtained atabout 1 kV.
•The contact angle of a water droplet at asurface of the glass panel decreased after
microplasma
treatment
from
41.5°to8.5°after 30 seconds. This recommends
microplasma as a solution for the surface
treatment of glass panels used in electronic
industry.